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RR926 On-tool controls to reduce exposure to
Health and Safety
Executive
On-tool controls to reduce exposure to
respirable dusts in the construction industry
A review
Prepared by the Health and Safety Laboratory
for the Health and Safety Executive 2012
RR926
Research Report
Health and Safety
Executive
On-tool controls to reduce exposure to
respirable dusts in the construction industry
A review
Dom Pocock
Health and Safety Laboratory
Harpur Hill
Buxton
Derbyshire
SK17 9JN
Many processes in the construction industry create large quantities of dust; often materials used in
construction contain silica. If the dust emissions from these processes are not controlled they can cause
exposures that exceed UK workplace exposure limits and consequently lead to occupational diseases
such as cancer, silicosis, chronic obstructive pulmonary disease and asthma. A common way to control
these hazards is to apply local exhaust ventilation (LEV). However, construction sites tend be temporary
workplaces, which makes the application of traditional LEV difficult. One solution is to affix LEV to the tool
being used or to use another mobile form of on-tool control such as water suppression.
The objective of this project was to conduct a review of the literature on the subject of the effectiveness of
on-tool controls and to summarise this information for HSE. The main findings were that:
g
On-tool LEV is capable of reducing exposures by 90% or more.
g
Important factors in achieving this reduction is hood design and choice of vacuum extraction source.
g
Even with exposure reductions of 90 %, on-tool controls never completely eliminated exposure. This may
mean that the use of supplementary respiratory protective equipment (RPE) is required, especially where
materials contained silica.
This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents,
including any opinions and/or conclusions expressed, are those of the author alone and do not necessarily
reflect HSE policy.
HSE Books
© Crown copyright 2012
First published 2012
You may reuse this information (not including logos) free of
charge in any format or medium, under the terms of the
Open Government Licence. To view the licence visit
www.nationalarchives.gov.uk/doc/open-government-licence/,
write to the Information Policy Team, The National Archives, Kew,
London TW9 4DU, or email [email protected]
Some images and illustrations may not be owned by the
Crown so cannot be reproduced without permission of the
copyright owner. Enquiries should be sent to
[email protected]
ii
KEY MESSAGES • Many construction activities such as grinding, finishing, polishing, mortar removal, sanding
and cutting produce large quantities of dust including materials containing silica and
gypsum in the inhalable and respirable size fractions and if uncontrolled can cause exposure
exceeding UK occupational exposure limits.
• A large body of work has been carried out in the last 10 – 15 years on controls. These
studies have demonstrated that significant reductions in exposure to workers in excess of
90 % are achievable for the following activities; tuck-point grinding, surface grinding and
polishing, floor sanding, drywall sanding and block, slab and tile cutting using both on-tool
LEV and water suppression methods.
• Where the two on-tool methods were directly compared there was often no significant
difference in control effectiveness.
• The choice of vacuum source is critical, maintaining the vacuum flow rate is vital. To do
this, the studies reviewed indicated that vacuum cleaners with cyclone type pre filters are
desirable or a vacuum fitted with an automatic back flush system.
• Although the European standard states that class H vacuums should be used for
carcinogenic materials several studies have shown that maintaining an adequate volume
flow rate is easier with a class M vacuum cleaner. Maintaining an adequate volume flow
rate is vital to achieving good capture and control of process generated dusts. It should be
recommended that for silica containing dusts a minimum of a class M vacuum cleaner
should be used.
• For applications such as tuck-point or surface grinding a minimum volume flow rate of
50 m3h-1 (30 cfm) is required to maintain good control but volume flow rates of 80 –
130 m3h-1 (50 – 80 cfm) are recommended, the European standard states that vacuum
cleaners should be fitted with a low flow alarm when extract velocity in the largest diameter
duct falls below 20 ms-1, this equates to approximately 140 m3h-1.
• On-tool controls should be considered as a complete system, where vacuum cleaner/extract
units that have been matched to specific tools should be used for best results.
• Water suppression methods were often considered to be unfavourable in some applications
for both safety and quality control reasons.
• Some studies found that the application of on-tool LEV did not significantly reduce
exposure and in one case actually increased it before modifications were made, hood
design/position/use was found to be critical in achieving effective removal of dusts. Some
studies found that only partial reductions in exposure were achievable.
• Even with exposure reductions in excess of 90 %, with many construction materials
containing respirable crystalline silica the use of supplementary respiratory protective
equipment (RPE) may be necessary to meet exposure limits.
• Many workers using these on-tool controls complained that the addition of extraction hoses
or water tanks made the tool heavier and more difficult to use and sometimes compromised
their productivity.
iii
iv
EXECUTIVE SUMMARY Objectives
Many processes in the construction industry create large quantities of dust; often materials used
in construction contain silica. If the dust emissions from these processes are not controlled they
can cause exposures that exceed UK occupational exposure limits and consequently lead to
occupational diseases such as cancer, silicosis, chronic obstructive pulmonary disease and
asthma. A common way to control these hazards is to apply local exhaust ventilation (LEV)
however, construction sites tend be temporary workplaces, which makes the application of
traditional LEV difficult. One solution is to affix LEV to the tool being used or to use another
mobile form of on-tool control such as water suppression.
Much of the information held by HSE on on-tool controls requires updating and there has been
much research carried out in the field in recent years. The objective of this project was to
conduct a review of the literature on the subject of the effectiveness of on-tool controls and to
summarise this information for HSE.
Main Findings
On-tool LEV is capable of reducing exposures created by processes such as; tuck-point grinding
to remove mortar, surface grinding, finishing and polishing, block, slab, brick and tile cutting,
floor and drywall sanding. In most cases exposure reductions of greater than 90 % were
achieved, sometimes after modifications to the LEV hood. Water suppression was found to be
an effective on-tool control for reducing exposure to respirable dusts. Where the two on-tool
control methods were compared no significant differences were found.
The volume flow rate of air for good on-tool control required is typically 50 m3h-1 as a
minimum but ideally 80 – 130 m3h-1 is recommended. The choice of vacuum source is vital;
typically industrial vacuum cleaners are used, which tend to recirculate air back into the
workplace. It is important that they have a final filter with a filtration efficiency of at least 99 %
to prevent reintroducing captured respirable dusts back into the workplace air. To this end
vacuum cleaners with cyclone type pre-filters are desirable or a vacuum fitted with an automatic
back flush system to maintain adequate volume flow rates. Where dusts containing crystalline
silica are produced a minimum of a Class M vacuum cleaner with final filter efficiency greater
than 99.9 % should be used. When using water suppression, the importance of the volume flow
rate of water was not widely agreed upon. Although where it was considered a flow rate
0.5 lmin-1 was considered to be a minimum.
Even with exposure reductions of 90 % and greater, on-tool controls never completely
eliminated exposure and could not always reduce it to below occupational exposure limits,
especially where materials contained silica. This may mean that the use of supplementary
respiratory protective equipment (RPE) is required. It should be noted however that most of the
studies reviewed measured task-based exposure and not whole shift exposure and that 8-hour
time weighted average (TWA) exposures may be lower, especially where workers perform
different tasks throughout the day.
The use of on-tool controls was not without issue. Many workers commented that the addition
of extraction hoses or the need to carry or move water tanks made the tools ergonomically
difficult to use and adversely affected their productivity. Some field studies noted that as
operators became more familiar with new tools the effectiveness of the controls improved. This
v
shows that where new tools and controls are to be applied training will be an important part of
achieving good control.
An internet search was conducted to determine the types and availability of on-tool extraction
devices. A wide range of power tools fitted with extraction and dust control devices were
available for purchase or hire either direct from manufacturers or from retailers and hire
companies. Most companies offering extracted tools also offered vacuum cleaners/extraction
units; most were of unspecified dust class. Vacuum cleaner manufacturers tended to be those
who specify the dust class. L and M class vacuum cleaners were widely available, H class
vacuum cleaners were only available from a limited number of suppliers.
vi
CONTENTS PAGE
1. INTRODUCTION ........................................................................ 1
2. IMPLICATIONS.......................................................................... 2
3. METHODOLOGY ....................................................................... 3
4. RESULTS................................................................................... 5
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
Construction activities and exposures studied
Tuck-point grinding (Mortar removal)
Surface Grinding (Finishing)
Cutting (Concrete, tiles & Bricks)
Other Applications
Vacuum sources for on-tool controls
Discussion and Conclusions
Availability of on-tool controls in the UK: As of November 2011
5
5
7
9
10
11
12
14
5. REFERENCES ......................................................................... 16
6. APPENDIX I – ON-TOOL CONTROLS USED IN STUDIES
REVIEWED..................................................................................... 19
vii
viii
1. INTRODUCTION Many processes in the construction industry in general and stone masonry in particular are
highly energetic and create large quantities of inhalable and respirable dust. Uncontrolled
emissions of these dusts present significant risks to workers’ health. These dusts may contain
respirable crystalline silica (RCS), which is a group 1 human carcinogen[1] and exposure to
them can lead to the development of silicosis, lung cancer and chronic obstructive pulmonary
disease (COPD). In addition respirable wood dusts can also be respiratory sensitizers, which can
cause occupational asthma. There is a requirement under the Control of Substances Hazardous
to Health (COSHH) regulations to eliminate or prevent such exposures. Where this is not
possible, such emissions must be adequately controlled to reduce exposure to below the
occupational exposure limit. One of the most effective controls is the application of local
exhaust ventilation (LEV) to control emissions at source.
Traditionally, in industries such as stonemasonry dust control is often achieved through the use
of capturing or receiving hoods, but these need to be frequently repositioned in order to function
effectively. In the construction industry where the location of work changes frequently often no
such controls are used. During a study of dust exposures to 1335 construction workers in the
Netherlands Nij et al (2003) found that only 9 % used external LEV, 14 % used on-tool LEV
and 66 % of respondents relied upon respiratory protective equipment (RPE) to control dust
exposure[2].
On-tool controls are integrated or mounted onto the tool and therefore move with the source of
the dust generation. As such it can provide a high standard of control and offers a possible
alternative method of traditional LEV control. On-tool extraction has been considered before
but much of the information held by HSE on the use and efficacy of these controls is old and
dates back to the late 1980s. Since then, there has been significant progress in the design and
use of on-tool controls.
This project was commissioned to conduct a review of the current literature on the subject of
on-tool controls, including extraction and water suppression and to summarise this information
for HSE.
1
2. IMPLICATIONS The findings of this literature review will better inform HSE policymakers and inspectors of the
abilities of on-tool controls to reduce respirable dust exposures to construction workers and
allow them to further consider the inclusion of on-tool controls in guidance and
recommendations to the construction sector.
The review of approximately 30 studies on the effectiveness of both on-tool LEV and on-tool
water suppression methods applied to construction related processes, such as tuck-point
grinding, surface grinding, polishing, brick, block and tile cutting, floor and dry-wall sanding is
capable of producing significant reductions in exposures to dusts in some studies. Where
materials containing silica were used it may be necessary to use supplementary RPE, as
exposure was not always reduced to below the workplace exposure limit (W.E.L) of 0.1 mgm-3
[3].
The studies have shown that the two main factors to consider when selecting an on-tool LEV
control are hood design and air volume flow rate. The use of tools with well-designed integrated
LEV hoods are preferable to retrofitted or after market systems. The choice of vacuum source is
instrumental in achieving and maintaining a sufficient volume flow rate. To do this, the studies
reviewed indicated that vacuum cleaners fitted with cyclone type pre filters or automatic back
flush systems are desirable. Class L vacuums are for dusts with an occupational exposure limit
grater than 1 mgm-3, Class M for dusts with an occupational exposure limit of no less than 0.1
mgm-3 and Class H vacuums are for dusts with all exposure limits including carcinogenic and
pathogenic materials. Whilst Class H vacuum cleaners have higher filtration efficiency than
Class M it can be more difficult to maintain a sufficient volume flow rate to provide good
capture and control of process generated dusts. For this reason, a Class M vacuum cleaner as a
minimum should be used in on-tool control systems for use in construction related tasks.
The information gathered in this literature review is not specific to the construction sector and
the lessons learned could be applied to any sector where these tasks are performed.
2
3. METHODOLOGY
A set of key words was defined to perform the literature search. These included terms for
airborne contaminants such as dust, mist and fume, relevant sectors such as construction,
building and stone masonry, tasks that were likely to produce airborne contaminants such as
drilling, grinding and sanding and interventions of interest such as ventilation and extraction.
These terms were formatted into a viable search strategy by the HSE search team in consultation
with the author; the search strategy used is given below.
mist or mists or dust or dusts or silica or gypsum or wood or lead or masonry or
concrete or brick or stone or metal*
AND
construction or build* or tool or tools or vacuum or ventilat* or scabbler* or grinder* or
saw or saws or sander or sanders or chisel* or drill* or router or routers or scaler or
scalers or hammer* or weld* or grinding or scabbling or sanding or cutting or chiselling
or routing or exhaust* or “low volume high velocity” or lev or lvhv or scarifying or
chipping or polishing or burning or plastering or gouging or screeding or seaming or
pointing or sweeping or scaling or splitting or breaking or jointing or raggling or harling
or stippling or chasing or sawing or mixing
AND
“technology control*” or “engineering control*” or ((control* or captur*) near5 (expos* or
emission* or emit* or efficien* or effect* or extract* or evaluat*))
(* = truncation)
This strategy was used to search a number of databases including Web of Science, Oshrom,
OshUpdate, ANTE and Iconda. In addition the author performed several internet searches and
searches of specific journals such as Annals of Occupational Hygiene, Journal of Applied
Occupational and Environmental Hygiene and the Journal of Occupational and Environmental
Hygiene. These searches produced approximately 200 articles, papers, policy, guidance and
review documents. The abstracts for these documents were sifted and the full texts of the
relevant articles were obtained. During the review several other referenced papers that hadn’t
been identified in the original search were added, in total 36 documents were selected and
reviewed.
The documents fall into four broad categories; the first is policy or guidance documents similar
to HSE Information Sheets, these are generic and do not contain any measured exposure data.
The second category is articles from peer reviewed scientific literature that do not directly report
or contain any measured exposure data such as literature review articles or studies from the
social sciences concentrating on perceptions of risk or the implementation of control strategies.
The third category is papers or reports that are not published in scientific peer reviewed
journals, but are technical reports from organisations such as National Institute of Safety &
Health (NIOSH) or the Health and Safety Laboratory (HSL), these contain measurements of
exposure and control intervention assessments. The final category is articles from peer reviewed
scientific journals that directly report work containing exposure measurements and/or measured
effectiveness of control interventions using on-tool controls.
3
Articles in the first and second categories are generally drafted and written using the data
gathered and lessons learned in the work reported in the third and fourth categories. Some of the
articles from the third category that were identified in the sift were later discarded as the data
from the work was subsequently published in an article that fell into the fourth category. The
findings and conclusions in this report are largely drawn from the articles from the third and
fourth categories. These are the ones that contain measured exposure caused by performing
construction tasks such as grinding, sanding, drilling and blasting and directly measure the
effectiveness of on-tool controls by comparing exposures with control on to control off.
4
4. RESULTS 4.1
CONSTRUCTION ACTIVITIES AND EXPOSURES STUDIED
The articles reviewed considered a variety of construction activities, these were; surface
grinding and finishing, tuck-point grinding (mortar removal), rock and surface drilling, sanding
(of drywalls, wood and refractory ceramic fibres), wood cutting and shaping, tile cutting, brick
and concrete block cutting and abrasive blasting. All of the tasks and activities mentioned above
were studied in at least one of the articles reviewed but the most studied were grinding and
cutting activities. Similarly, exposure to a variety of materials has been studied but by far the
most considered was exposure to silica caused by grinding or cutting concrete. Of the 36 articles
reviewed 25 were directly considering exposure to RCS from working with concrete. Other
materials considered were wood dust (3), gypsum containing drywall compound (2), refractory
ceramic fibres (1), lead and other metals (1). Three articles were sampling for unspecified dust
during rock drilling activities although it is likely that silica exposure would be an issue during
these activities. Not all articles that considered exposure directly measured exposure to silica,
rather to respirable dust, which is sometimes referred to as respirable suspended particulate
(RSP) matter.
4.2
TUCK-POINT GRINDING (MORTAR REMOVAL)
4.2.1
On-tool LEV
Tuck-point grinding is performed during the restoration of old brickwork. The old mortar is
removed to depth of 1 – 2 cm using a right angle grinder before the brickwork is re-pointed.
Grinding is a highly energetic process and creates large quantities of dust, Meeker et al (2009)
measured personal breathing zone exposures to RCS of 4.99 mgm-3 and 10.90 mgm-3 during
uncontrolled tuck-point grinding using two different right-angle grinders[4]. In a study for
NIOSH of RCS exposures in the construction industry in the U.S. Heitbrink et al (2000) found
exposures of 1 – 3 mgm-3 caused by tuck-point grinding[5]. In a study of the effectiveness of
on-tool LEV Croteau et al (2002) measured RCS exposures of 3.04 mgm-3 caused by
uncontrolled tuck-point grinding[6]. These values were typical of the measured RCS exposure
caused by uncontrolled tuck-point grinding and fall within the range of 10 – 100 times the U.K.
8-hour Time Weighted Average (T.W.A.) Workplace Exposure Limit (W.E.L.) of 0.1 mgm-3 as
stated in the July 2006 addendum to EH40[3].
A total of nine articles reporting results from ten studies of on-tool controls for right-angle
grinders were reviewed, the control methods assessed had varying degrees of success. The
Heitbrink et al (2000)[5] evaluated on-tool controls in the field. Uncontrolled personal
exposures to RCS were measured to be 1 – 3 mgm-3 and total dust exposures of 24 – 442 mgm-3.
A Metabo right-angle grinder with an extracted shroud around the grinding wheel was tested;
personal exposures to RCS of 9.01 mgm-3 and total dust of 103 mgm-3 were measured. In this
case the control measure increased exposure to dust and in fact testing of the device was halted
because the dust exposures were excessive. The authors believed that the poor positioning of the
extracted shroud caused the increase in exposure. Nash et al (2000)[7] tested a right angle
grinder fitted with an extracted shroud, 8-hour TWA exposures to total dust were 22.4 mgm-3
and 16.3 mgm-3. Use of the on-tool LEV reduced these exposures to 11.4 mgm-3 and 8.6 mgm-3
respectively, reductions of 49 % and 47 %. The employees using the ventilated tool found it
cumbersome and difficult to use, following modification by the manufacturer the tool was
retested. This time 8-hour TWA exposure was reduced by 97 % from 94.6 mgm-3 to 3.0 mgm-3.
Following their study in 2000 Heitbrink and Bennett tested another on-tool LEV system for a
right-angle grinder[8]. They measured personal exposures of workers using the system of 0.94 –
5
4.0 mgm-3, there were no control off measurements but these exposures are consistent with
uncontrolled exposure levels reported elsewhere. The authors believed that the reasons for the
control failure included insufficient volume flow rate to the system (measured as approximately
19 m3h-1) and an inadequate filtration system.
Other studies found on-tool LEV systems for right-angle grinders to be more effective, in their
study of on-tool LEV for a variety of tasks Croteau et al [6] measured an 84 % reduction in
exposure to RCS (3.04 mgm-3 without control, 0.47 mgm-3 with) and an 80 % reduction in total
respirable dust (RSP) with a volume flow rate of 128 m3h-1. Shojiro et al (2003)[9] assessed
control of right-angle grinders using a traditional grinding disc and a mortar rake. The system
on the grinding disc reduced exposures to RCS by 98 % (2.84 mgm-3 without and 0.059 mgm-3
with control). The extracted shroud on the mortar rake reduced exposure by 81 %. Heitbrink
et al conducted a further study of three ventilated shrouds for right-angle grinders[10] one
manufactured by Dust Control (Wilmington, Delaware, USA), one by Zantech (Wayne, New
Jersey, USA) and a home made one. The study was conducted in the laboratory using an
automated traverse in a ventilated test chamber and sampling for emitted dust, thus not
measured personal exposure data but emitted dust per volume of mortar removed. Emission rate
with no control was 27 mgcm-3 of mortar removed. There was no statistically significant
difference in emission rates between the three different shrouds. With a volume flow rate
between 51 m3h-1 and 136 m3h-1 the average emission rate was 0.21 mgcm-3 of mortar removed
and with volume flow rate greater than 136 m3h-1 the average emission rate was 0.06 mgcm-3 of
mortar removed. Collingwood et al (2007)[11] performed a field evaluation of an on-tool LEV
system for a right-angle grinder measuring personal exposure to RCS. The geometric mean of
22 samples was 0.06 mgm-3 with a range of 0.01 mgm-3 to 0.86 mgm-3. There was no
measurement of control off exposure but previous work has shown uncontrolled exposures to be
up to 10 mgm-3. Finally Meeker et al (2009)[4] in their study of on-tool controls measured
reduction in exposure to RCS of 91 % for a Bosch grinder (4.99 mgm-3 reduced to 0.47 mgm-3)
and 97 % for Metabo grinder (10.90 mgm-3 reduced to 0.33 mgm-3).
The studies reviewed considered the various factors affecting the performance of on-tool LEV
for right-angle grinders. All the systems take the form of an extended shroud or guard around
the grinding wheel with a take-off for the exhaust, see Figure 1 below.
To
extract
Shroud
d
Grinding
wheel
Mortar
Figure 1 Illustration of a ventilated shroud for a right-angle grinder
The positioning of the extract take-off is important, it should be positioned to best intercept the
dust as it is thrown off of the rotating wheel, this was believed to be the problem with the
shroud tested by Heitbrink[5]. Collingwood and Heitbrink [10, 11] performed some
6
computational fluid dynamics (CFD) simulations of extracted shrouds. They found that the
particle stream emanating from the grinding wheel was the dominant factor inducing airflows
and should be the primary focus for design. They found that minimising the distance d between
the grinder shroud and the wall (see Figure 1 above) is vital in achieving good control and
preventing the dust from escaping the shroud. They also found that the volume flow rate of the
system is an important factor and recommend a minimum flow rate of 85 cfm (145 m3h-1). This
is in line with the experimental work carried out in the same study that found the three shrouds
to be more effective at volume flow rates in excess of 80 cfm (136 m3h-1).
An important part of achieving and maintaining the volume flow rate to the shroud is the
selection and operation of the vacuum unit. Heitbrink and Santalla-Elias (2009)[12] tested four
commercially available vacuum cleaners when used as a vacuum source for on-tool LEV during
tuck-pointing. All four vacuum cleaners had a final filter efficiency of at least 99.9 % at 0.3 μm,
two of them were 99.97 % at 0.3 μm. Two of the vacuum cleaners had cyclone type pre-filters
and the other two used traditional paper bag pre-filters. The vacuum filters fitted with cyclone
pre-filters were unaffected by debris build-up and the volume flow rate did not alter
significantly during testing. The volume flow rate of the two with bag pre-filters fell from 80
cfm (136 m3h-1) to as little as 30 cfm (51 m3h-1). This means that if vacuum cleaners with bag
pre-filters are used the pre-filter will have to be unblocked frequently to maintain the volume
flow rate to the shroud. It should be noted here that some systems are available with an
automatic ‘back-flush’ filter cleaning system, which would be beneficial for systems with bag
type pre-filters. Although no peer reviewed published information was found on evaluation of
these systems.
On-tool LEV applied to right angle grinders for mortar removal has been tested both in the field
and in a laboratory setting. The efficacy of the LEV controls has been found to range from
completely ineffective to being able to reduce exposure to respirable dusts by 99 %. The
primary factors affecting control performance are design of the hood or enclosure, user training
and operation of the tool, the volume flow rate and type of vacuum source used to move air
through the system and the location of the work taking place. Exposures outdoors tended to be
lower than those indoors, which is likely to be due to the dilution effect.
4.2.2
Water suppression
One study considered a water suppression system for a right-angle grinder. Heitbrink[5] fitted a
water suppression device to one of the right-angle grinders tested after the on-tool LEV device
had failed and retested it with a wet and dry vacuum cleaner. This reduced exposure to
0.38 mgm-3 (uncontrolled exposure 1-3 mgm-3) providing a maximum reduction in exposure of
87 %.
4.3
SURFACE GRINDING (FINISHING)
4.3.1
On-tool LEV
The second most studied construction task was surface grinding or finishing, predominantly of
concrete. This ranged from grinding large areas such as floors and walls to finishing beams and
pillars. This is again a highly energetic process with the potential to cause high exposures to
respirable dust and where the material being ground is concrete or stone potentially respirable
silica. Flanagan et al (2003)[13] measured exposure to respirable dust of 4.87 mgm-3, Ojima
(2007)[14] measured a concentration of metal dust of 7.73 mgm-3 approximately 40 cm from a
grinder in a test chamber, Croteau[6] measured exposure to RCS of 29.16 mgm-3 caused by
uncontrolled grinding and Akbar-Khanzadeh (2010)[15] measured exposure to RCS of
6.80 mgm-3 and RSP of 47.8 mgm-3 caused by uncontrolled surface grinding.
7
On-tool LEV for surface grinding was found to have varying levels of success, Ojima[14]
assessed the effectiveness of a ventilated shroud supplied with a Hitachi grinder in a controlled
test chamber. The effectiveness was assessed by measuring respirable dust approximately 40 cm
from the grinder with and without control whilst grinding weld beads that had been laid down
on a test piece of metal. The shroud reduced the concentration of respirable dust outside of the
grinder shroud by 37 %, 7.73 mgm-3 without control, 4.87 mgm-3 with control. Flanagan[13]
studied RCS exposures during a variety of construction activities including concrete cutting,
mixing, grinding, tuck-point grinding, sacking and patching and floor sanding. They observed
that dust controls were used during only 12 % of tasks studied; personal exposure to RCS was
measured during a surface grinding operation. The on-tool LEV reduced exposure by 71 % from
4.87 mgm-3 to 1.42 mgm-3. A box fan providing general area ventilation was found to reduce
personal exposure to RCS during a similar task by 57 %.
Echt et al (2002)[16] performed a field study of on-tool controls on surface grinders being used
by construction workers. A variety of grinders were used but they were all fitted with a
Vacugaurd ventilated shroud manufactured by Pearl Abrasive Co. and connected to a
Dustcontrol H-type vacuum cleaner. Personal samples were collected over a full shift and
exposures reported as an 8-hour TWA. Exposure to silica over five days ranged from
0.036 mgm-3 to 0.13 mgm-3 and respirable dusts 0.55 mgm-3 to 1.2 mgm-3. There were no
measurements taken with the control off but comparing these exposures to exposures measured
from uncontrolled grinding in other studies shows that exposure was being well controlled. The
sampling periods over the five days ranged from 265 minutes to 340 minutes so they represent a
high level of control over a whole shift. Additionally, workers on the site provided anecdotal
evidence that dust emissions were well controlled. The author states that, “The concrete finisher
reported that electricians had told him that they didn’t need to clean concrete dust from the light
fixtures they were installing, and that form crews were able to work nearby, stripping forms,
while grinding was conducted. Uncontrolled grinding would not have allowed this to occur.”
Croteau [6] assessed the effectiveness of a ventilated shroud on a surface grinder in a laboratory
study. The on-tool control reduced personal exposure to RCS by 94 %, 29.16 mgm-3 without
control and 1.70 mgm-3 with control running at 128 m3h-1, this was reduced to a 92 % reduction
(personal exposure 2.36 mgm-3) when volume flow rate was reduced to 51 m3h-1. Shepherd et
al[17] performed a case study investigating the social sciences aspect of applying exposure
controls in the construction industry. Whilst there was no measurement of exposures or
assessment of controls they do discuss the application of an on-tool control used during grinding
of concrete ceilings on a construction site that maintained workers exposure below the
Occupational Safety and Health Administration (OSHA) WEL.
Akbar-Khanzadeh et al have performed three studies on the effectiveness of on-tool LEV for
grinders in the last ten years. In 2002[18] they performed a field study measuring exposures to
RCS of 17 concrete finishers. Data for a total of 64 shifts was collected, 15 of the shifts were
performed using on-tool LEV. Task mean exposure to RCS for no control was 1.50 mgm-3 and
for respirable dust 24.3 mgm-3. For shifts with LEV control the mean RCS exposure was
0.38 mgm-3 and respirable dust 5.49 mgm-3, which is a 75 % reduction in RCS and 77 %
reduction in respirable dust. When these task-based exposures were converted to 8-hour TWA
exposures 14 of the 15 with LEV control were below the OSHA Permissible Exposure Limit
(PEL). In 2007[19] they performed a laboratory study comparing the effectiveness of on-tool
LEV and water suppression to uncontrolled grinding. They found that the on-tool LEV reduced
the exposure to RCS from 25.4 mgm-3 with no control by 99 % to 0.148 mgm-3, wet grinding
reduced the exposure by 98 % to 0.521 mgm-1. Statistical analysis showed that there was no
statistically significant difference between the two control measures. Similar reduction were
found for exposure to respirable dust, on-tool LEV reduced exposure by 99 % (228 mgm-3 with
8
no control, 1.82 mgm-3 with control) and wet grinding by 97 % (7.77 mgm-3 with control).
Again there was no statistically significant difference between the two control methods.
Akbar-Khanzadeh et al[15] conducted a study of on-tool controls for surface grinders in
controlled conditions. They investigated several parameters; the effect of general ventilation,
orientation of surface being ground, size of angle grinder and grinding wheel, and a variety of
control combinations. The control combinations were LEV with a HEPA filtered vacuum
cleaner, LEV with a standard vacuum cleaner, wet grinding and water volume flow rate and
uncontrolled grinding. They found that LEV with the HEPA filtered and standard vacuum
cleaners reduced respirable dust exposure by 99 % and 97 % respectively. Wet grinding reduced
respirable dust exposure by 93 %, there was no statistically significant difference between LEV
and water control. The general ventilation applied was 62 air changes per hour (ach), this is
extremely high and would be the equivalent of working inside a ventilated booth, and would be
unlikely to be found on a construction site unless working outdoors. The study found that this
level of general ventilation reduced exposure to RCS and respirable dust by 66 % and 70 %,
however I feel that it would be impractical to achieve this level of ventilation without building a
ventilated enclosure to contain the work. The study found that larger grinders produce more dust
and that reductions in dust exposure decreased with the larger grinders which used larger
diameter wheels , this is expected because the same vacuum cleaners were used and the larger
diameter grinding wheels would require a higher volume flow rate. It was found that the
orientation of the work piece, the water volume flow rate, and the smaller grinder sizes (100,
115 and 125 mm wheels) did not have a statistically significant effect on control efficiency.
On-tool LEV for use with surface grinders has been tested in the field and in the laboratory in a
variety of configurations. It has been found to be able to provide exposure reductions from 37 %
to 99 % depending on the application. Factors affecting performance are again maintaining an
adequate volume flow rate to the hood and user training and operation. Anecdotally
construction workers have found the tools harder to use than tools without on-tool controls,
specifically finding them more cumbersome to manoeuvre because of the added weight of the
extraction hose. Several workers also reported that using the on-tool devices reduced their
productivity although his may be the effect of using a new tool.
4.3.2
Water suppression
Only the two studies by Akbar-Khanzadeh considered the use of water suppression as an
alternative control to on-tool LEV [15, 19]. In both studies water suppression was compared to
on-tool LEV. In both cases there was no statistically significant difference in the reductions in
exposure to respirable dust.
4.4
CUTTING (CONCRETE, TILES & BRICKS)
A number of studies have been carried out assessing on-tool controls for cutting activities such
as cutting concrete blocks and paving slabs, cutting bricks and cutting roofing tiles using hand
held saws and stationary chop and cut-off saws. Exposures to respirable dust have been
measured at up to 50 mgm-3[20] when using these types of tool. Sheehy et al[21] performed a
field evaluation of three hand-held masonry saws and a manual tile cutter. One of the saws
(Partner) was fitted with a water suppression system fed by a backpack water tank; another
(Bosch) was fitted with a ventilated shroud and connected to a vacuum cleaner and a third
(Revelation) had an after market dust collection system consisting of an axial fan and a shroud
collecting dust in a filter bag. Testing with the Revelation saw was immediately abandoned
because in order to fit the dust collection system the blade guard had to be removed which was
deemed unsafe by the roofer. The Partner saw was considered unsuitable for use on a roof
because of the weight of the backpack and that the water presented a slipping hazard and as
9
such was only tested on the ground. The Bosch saw was also considered unsuitable for use on a
roof due to the dragging effect of the exhaust hose and was also only tested on the ground.
When using the Partner saw with the water suppression the personal exposure to respirable dust
ranged from 4.80 mgm-3 to 8.2 mgm-3. When using the Bosch saw the personal exposure to
respirable dust was 2.51 mgm-3 and when using the manual tile cutter respirable dust exposure
never exceeded 0.12 mgm-3. Whilst the manual cutter did not produce significant amounts of
dust the roofers felt that it was not suitable for cutting roofing tiles neatly.
Thorpe et al[20] conducted a study of controls on three cut-off saws in the construction
industry, the controls tested were; water suppression from a pressurised tank, water suppression
from mains water and an on-tool LEV system each using a resin bonded blade and diamond
tipped blade. Exposures to respirable dust were reduced by 94 %, 96 % and 91 % for the
pressurised water, mains water and LEV controls respectively using a diamond tipped saw. For
the resin bonded saw, exposures to respirable dust were reduced by 47 %, 97 % and 98 % for
pressurised water, mains water and LEV respectively. The authors believed that the poor control
reduction for the pressurised water system was caused by the resin bonded blade taking longer
to make the cuts and requiring the water tank to be re-pressurised. The mass of RCS collected
onto the filters was below the limit of detection for all three ‘control on’ scenarios making it
difficult to accurately measure the reduction in RCS exposure. Additional work was carried out
in the laboratory to assess the effect of water volume flow rate on control effectiveness.
Respirable dust concentrations were measured using water flow rates of 0.12, 0.20, 0.50 and
1.0 lmin-1, the reductions in respirable dust concentration were 55 %, 73 %, 97 % and 98 %
respectively. This suggests that when water suppression is used on a hand-held cut-off saw the
volume flow rate should be a minimum of 0.50 lmin-1.
Croteau[6] assessed the effectiveness of a masonry saw and hand held saw for block and brick
cutting. The masonry saw for block cutting produced a 96 % reduction in RCS exposure and a
90 % reduction in respirable dust. The hand held saw for brick cutting produced an 86 %
reduction in RCS exposure but no measurements of respirable dust were made. Meeker et al[4]
measured RCS exposure during block and brick cutting using a hand-held saw fitted with
on-tool LEV and a stationary wet saw in the field. When cutting blocks the saw with LEV and
wet saw produced reductions in RCS exposure of 96 % and 93 % respectively (0.11 mgm-3,
0.21 mgm-3 controlled and 2.83 mgm-3 uncontrolled). When brick cutting the reductions in RCS
exposure were 91 % for both controls (0.08/0.09 mgm-3 controlled and 0.94 mgm-3
uncontrolled). Carlo et al (2010)[22] performed a laboratory evaluation of an on-tool LEV and a
water suppression system for a hand-held masonry saw. The water suppression system reduced
exposure to respirable dust by 99 % and the LEV system by 88 %.
Shepherd et al (2008)[23] evaluated an on-tool system for a hammer drill, two hood types and
two vacuum cleaners were assessed. Exposure to RCS was reduced by 91-98% by the four
combinations (0.308 mgm-3 uncontrolled, 0.006 – 0.028 mgm-3 controlled).
4.5
OTHER APPLICATIONS
Two articles were found that considered control of dust emissions from sanding internal
drywalls comparing the effectiveness of dust control from hand sanding, pole sanding, wet
sponge sanding and a ventilated sander. A review article authored by NIOSH[24] states that
drywall sanders can be exposed to dust levels in excess of 15 mgm-3, the UK WELs for
inhalable and respirable gypsum dust, which is one of the main drywall compound ingredients,
are 10 mgm-3 and 4 mgm-3 respectively[3]. The NIOSH article advises that the use of vacuum
sanding tools can reduce exposure by 80-97 %. Young-Corbett et al (2009)[25] compared hand
sanding to pole sanding (hand sanding with the use of a pole to separate the workers breathing
10 zone from the dust source), wet sponge sanding and vacuum sanding. They found that
exposures were reduced by 58 %, 60 % and 88 % respectively.
Potts and Reed (2009, 2010)[26, 27] performed two studies investigating dust emissions from
surface drilling. These types of drill are encased in an enclosure called the drill shroud that is
extracted. Air is supplied down the drill sleeve which then exits and enters the drill shroud
carrying dust with it, the moving air then forms a rolling eddy inside the shroud and dust laden
air leaks around the bottom edges despite air being extracted from the shroud. The study
investigated the addition of a blocking shelf inside the enclosure to break up the eddy and
redirect the air toward the exhaust, this reduced dust concentrations measured outside of the
drill shroud by 81 %. The second study investigated the use of compressed air jets to further
improve containment of dust-contaminated air inside the drill shroud. The system they designed
and tested reduced the concentration of dust outside of the enclosure by 48 – 52 %.
Several articles concerning on-tool controls for woodworking were identified, however none of
them contained systematic assessments of effectiveness or measured exposure reductions.
Although they were outside of the scope of this literature review HSL have recently carried out
two projects assessing the effectiveness of on-tool controls for arc welding and for soldering,
which showed that on-gun LEV for these applications could be highly effective. For on-gun
welding capture efficiencies were generally greater than 90 % except for when welding in the
interface between horizontal/vertical fillets[28]. For soldering, the use of on-tool LEV in the
form of a small capturing hood positioned 5 – 10 mm from the soldering iron tip was able to
reduce exposure to colophony fume by 100 %.
4.6
VACUUM SOURCES FOR ON-TOOL CONTROLS
The majority of the studies considered in this review tended to concentrate on the hood end of
the LEV system and this is a typical approach from an occupational hygiene perspective with
the justification that if contaminants do not enter the hood or enclosure then the rest of the
system is redundant. However, a majority of the studies conclude that the volume flow rate
generated by the LEV system is an important factor in achieving good control. The vacuum
source, which would typically be a mobile industrial vacuum cleaner on a construction site, and
filtration system are vital in creating and maintaining a sufficient volume flow rate to achieve
good control.
Heitbrink and Santalla-Elias studied the effect of filter loading on volume flow rate using four
commercially available vacuum cleaners during tuck-pointing operations[12]. They primarily
compared two with cyclone type pre-filters to two using traditional bag type pre-filters. The
study showed that the vacuum cleaners fitted with cyclone pre-filters suffered virtually no
decrease in volume flow rate whilst the two vacuum cleaners with bag pre-filters suffered a
decrease in volume flow rate of up to 60 % caused by filter loading. This would mean that
vacuums fitted with bag type pre-filters would require more regular filter cleaning or bag
replacement to maintain sufficient volume flow rates compared to vacuums with cyclone prefilters, or be fitted with an automatic ‘back-flush’ system.
There is a European standard, EN 60335-2-69:2009 [29] regarding the use of vacuum cleaners
and dust extractors for the collection of hazardous dusts. This standard defines the operating
characteristics of L, M and H type vacuum cleaners, these are summarised in Table 4.1 below.
11 Table 4.1 Performance characteristics of L, M and H type vacuum cleaners
Dust Class
Suitable for hazardous dusts with occupational exposure limits
mgm-3
Final filter efficiency
%
L
>1
> 99
M
≥ 0.1
> 99.9
H
< 0.1
> 99.995
L-type (Light hazard) vacuum cleaners are suitable for separating dusts with an occupational
exposure limit of greater than 1 mgm-3. M-type (Medium hazard) vacuum cleaners are for
separating hazardous dusts with an occupational exposure limit of not less than 0.1 mgm-3. Htype (High hazard) vacuum cleaners are for separating dusts with all occupational exposure
limits including carcinogenic and pathogenic dusts. At first glance this suggests that both H and
M type vacuum cleaners would be suitable for controlling dust emissions from processes
creating respirable crystalline silica dust. The 8-hour TWA exposure limit for RCS is 0.1 mgm-3
[3], this puts it on the limit between using an M type or H type vacuum cleaner. However,
respirable crystalline silica dust is classified by the International Agency for Research on
Cancer (IARC) as a group 1 human carcinogen[1]. This classification clouds the issue of which
class of vacuum cleaner to use for silica containing materials. BG BAU in Germany conducted a
significant body of work in which the capturing efficiency over 100 combinations of power
tools fitted with on-tool controls and vacuum cleaners were measured[30]. The main conclusion
of this study was that the systems with the most successful dust controls were those that used
harmonised systems, i.e. an on-tool control matched to the correct vacuum cleaner, usually one
from the same manufacturer. They also found that Class M vacuums tended to be less
susceptible to filter loading and thus maintained the correct volume flow rate for longer than
compared to class H vacuums. Whilst the filtration efficiency of a class H vacuum is higher this
only related to material removed from exhausted air, if the dust-laden air is not captured by the
LEV in the first pace the vacuum cleaner filter would remove none of the contaminant dust.
This coupled with the fact that class M vacuums are more readily available than class H it
would seem sensible to specify that for processes releasing silica containing dusts a minimum
of a class M vacuum cleaner should be used.
The standard recommends that vacuum cleaners have a low flow warning when the velocity in
the largest diameter hose falls below 20 ms-1. If we assume that the mean diameter of the largest
hose on an industrial vacuum cleaner is 50 mm this is equivalent to a volume flow rate of
140 m3h-1. This is comparable to or higher than most of the minimum volume flow rates quoted
in the studies reviewed. Two are slightly higher or come close to this value, Collingwood and
Heitbrink[10, 11] recommend a minimum volume flow rate of 145 m3h-1 for tuck-pointing
operations and Flynn et al[31] recommend 43 m3h-1 per inch of grinding wheel for tuck-pointing
which would exceed the 140 m3h-1 for anything larger than a 3 ¼” grinding wheel.
Much of the detail of the standard is concerned with the electrical safety of vacuum cleaners;
other relevant material concerns the required regular maintenance. Specifically those for H-type
vacuum cleaners the internal parts are treated as being contaminated and only opened by trained
individuals wearing suitable PPE. The essential (final) filter should be tested for filtration
efficiency at least every year.
4.7
DISCUSSION AND CONCLUSIONS
One of the most important factors in achieving good control using any LEV system and on-tool
systems in particular is hood design. Many on-tool extraction devices are added as an after
thought or retrofitted to existing tools. Whilst this approach can be effective in can detrimentally
12 affect the effective use of the tool by the user and if poorly designed can also reduce control
effectiveness. Some modern on-tool controls have been designed as an integral part of the tool
and are often positioned so as to maximise the use of any air movement generated by the tool –
such as spinning discs of grinders of saws – to intercept the contaminant laden air and to ensure
that the extraction does not hinder the effective use of the tool. A good example of this is the
evolution of on-tool extraction applied to arc welding torches. The early versions in the 1970s
had large and bulky hoods bolted onto existing torches, anecdotally these made the torches
heavier and more difficult to use with the dragging effect of the extract duct and also impaired
visibility of the work. Modern extracted welding torches have the hood built into the torch and
extract ducting integrated as part of the existing hose carrying coolant and the welding wire, this
makes the torches considerably more acceptable to operators.
Whilst many factors are important when selecting on-tool controls the two main things to
consider are the hood as discussed above and selecting the correct vacuum source to provide
and maintain sufficient volume flow rate. As discussed above a system with integrated
extraction is preferable to one where a hood has been retrofitted to a tool and vacuum for those
systems investigated, cleaners with cyclone type pre-filters are preferable to those with bag type
pre-filters. These factors were considered and investigated in detail by the BG-BAU study on
on-tool controls[30]. The two main conclusions from this study were that harmonised systems
had a higher potential for exposure reduction and that a well-designed hood is critical to
achieving adequate dust control. A harmonised system is defined as one where tool,
capturing/containing device and vacuum cleaner/extract unit are designed to work together as an
integrated system. The work by BG-BAU showed that for much construction related work such
as wall chasing/tuck-pointing, concrete grinding, concrete/stone cutting, plaster milling and
sanding most on-tool controls were capable of reducing dust exposures below exposure limits,
some of their conclusions are given below.
“Most of the tested systems show at least adequate efficiency”
“The essence in future will be to prompt the firms only to use power tool systems recommended
and harmonised by the manufacturers”
“An important factor for high efficiency of the seizing [capture] element is a hood as closed as
possible guiding the exhaust air as optimal[ly] as possible. Necessary intakes have to placed in
the right positions.”
Finally, Flynn et al (2003)[31] conducted a review similar to this report, a few of their
comments were as follows:
“Exposures to dust and silica during surface grinding of concrete are reduced with both local
exhaust ventilation and with wet methods. However, few of the studies provided adequate detail
to come to definitive conclusions, and further studies are needed to document the required air
flow rates for hoods.”
When considering tuck-point grinding:
“Results to date suggest that ventilating the enclosing shroud at a rate of 20 – 25 cfm (34 –
43 m3h-1) per inch of wheel or blade diameter is required to minimize dust generation.”
And cutting:
“The use of wet methods and LEV provide significant reductions in exposures for cutting
operations using either fixed or hand held masonry saws.”
13 And in conclusion:
“…, it is clear that technology is currently available to provide dramatic reductions in
exposure.”
Regarding the first comment from Flynn, since 2003 a number of studies have been completed
that demonstrate that on-tool LEV applied to surface grinders is capable of producing
significant reductions in exposure to respirable dusts. Some of the studies investigated the effect
of volume flow rate upon control effectiveness. A minimum volume flow rate of 50 m3h-1
(30 cfm) is required to maintain a capture efficiency greater than 90 % and a flow rate of 80 –
100 m3h-1 would be recommended to allow for some decrease in volume flow rate caused by
filter loading in the vacuum source.
Having reviewed a large quantity of literature on the subject it seems clear that on-tool controls
exist that are capable of reducing exposure to respirable dusts including silica by greater than
90 % for construction activities such as mortar removal, concrete grinding and finishing, block,
tile and brick cutting and sanding. However, in the case of silica because the activities
concerned produce high quantities of respirable dust and the need to reduce exposure as far
below the challenging exposure limit it may still be necessary to combine on-tool controls with
supplementary RPE. The exposure reductions provided by on-tool controls may remove the
need for full-face air fed respirators in favour of half face filtering masks with lower assigned
protection factors, although it should be noted that protection level is only one factor in
selecting RPE. Proper training in the use of tools fitted with controls is vital as it may be
necessary to alter methods of working in order to maximise the effectiveness of controls.
In those studies where water suppression as an on-tool exposure control was studied it was
found to be effective and where it was compared to on-tool LEV there was often no significant
difference in control effectiveness. There are some concerns using about using water
suppression in some applications. For instance in roofing activities the use of water suppression
would pose a significant slip risk on a roof and there are quality control issues with the slurry
staining roofing tiles. There are also some issues regarding electrical safety and the use of water
suppression, however for some applications there are pneumatic or electrically isolated tools
available.
It seems clear that without some form of exposure control, exposure to respirable dusts caused
by these construction activities is excessive. The majority of studies in this review measured
task-based exposure rather than full shift exposure and as many construction workers are likely
to vary their activities during the working day further studies measuring full shift exposures
whilst using on-tool controls would be beneficial in further assessing their capabilities.
4.8
AVAILABILITY OF ON-TOOL CONTROLS IN THE UK: AS OF
NOVEMBER 2011
A wide range of hand-held power tools fitted with on-tool extraction is available for sale and for
hire in the UK. These include mitre saws, cut-off saws, table saws, hand-held circular saws,
surface grinders, angle grinders, wall chasers, drills, hand-held sanders and floor and wall
sanders. An internet search was undertaken of the types and availability of on-tool extraction
devices in the UK. This was performed using internet search engines using combinations of the
following search terms:
Power tools, extraction, on-tool, dust control, dust extract, industrial vacuum cleaners, hire
Not all tools in any of the ranges available were fitted with a capturing hood and extraction
take-off port but most manufacturers offered at least some models with dust control fitted. Tools
14 fitted with extraction and dust control devices were available to purchase either directly from
the manufacturers or via retailers. Most tools fitted with on-tool controls were also available to
hire.
Most companies offering power tools also offered a number of vacuum cleaners/extraction
units. The majority of vacuum cleaners were of unspecified dust classes on websites, more
information was usually available if the company was contacted directly. Vacuum cleaner
manufacturers tended to be those who specify dust class. L and M class vacuum cleaners were
widely available, H class vacuums were available but from a limited number of suppliers which
tended to be companies specialising in extraction.
15 5. REFERENCES
1.
IARC, IARC Monograph on the Evaluation of Carcinogenic Risks to Humans: Volume
68 - Silica, Some Silicates, Coal Dust and Para-Aramid Fibrils, ed. IARC. Vol. 68.
1997. 506.
2.
Nij. E.T., Hilhorst.S., Spee. T., Spierings. J., Steffens. F., Lumens. M., Heederik. D.,
Dust Control Measures in the Construction Industry. Ann. Occup. Hyg., 2003. 47(3): p.
211-218.
3.
HSE, EH40/2005 Workplace exposure limits. 2nd ed, ed. H. Books. 2011: HSE Books.
74.
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Meeker. J.D., Cooper.M.R., Lefkowicz. D., Susi. P., Engineering Control Technologies
to Reduce Occupational Silica Exposures in Masonry Cutrting and Tuckpointing.
Public Health Reports, 2009. 124(1): p. 101 - 111.
5.
Heitbrink. W.A., In-depth Survey Report: Control Technology for Crystalline Silica
Exposures in Construction: Exposures and Preliminary Control Evaluation, in In-depth
Survey Reports, C. NIOSH, Editor. 2000, NIOSH: Cincinnati. p. 21.
6.
Croteau. G.A., Guffey.S.E., Flanagan. M.E., Seixas. N.S., The Effect of Local Exhaust
Ventilation Controls on Dust Exposures During Concrete Cutting and Grinding
Activities. AIHA Journal, 2002. 63(4): p. 458-467.
7. Nash. N.T., Williams.D.R., Occupational Exposure to Crystalline Silica During
Tuckpointing and the Use of Engineering Controls. Applied Occupational and
Environmental Hygiene, 2000. 15(1): p. 8-10.
8.
Heitbrink. W.A., Bennett.J.S., Control Technology for Crystalline Silica Exposures in
Construction: Exposures and Preliminary Control Evaluation at a Restoration
Preservation Masonry Construction Site, in In Depth Survey Report, C. NIOSH, Editor.
2000, NIOSH: Cincinnati. p. 14.
9.
Shojiro. Y., Susi.P., McClean. M., Flynn. M., Assessment of Silica Exposures and
Engineering Controls During Tuckpointing. Applied Occupational and Environmental
Hygiene, 2003. 18(12): p. 977-984.
10.
Heitbrink. W., Bennett.J., A Numerical and Exerimental Investigation of Crytalline
Silica Exposure Control During Tuckpointing. Journal of Occupational and
Environmental Hygiene, 2006. 3(7): p. 366-378.
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Collingwood. S., Heitbrink.W.A., Field Evaluation of an Engineering Control for
Respirable Crystalline Silica Exposures During Mortar Removal. Journal of
Occupational and Environmental Hygiene, 2007. 4(11): p. 875-887.
12.
Heitbrink.W.A., Santalla-Elias.J., The effect of debris accumulation on and filter
resistance to airflow for four commercially available vacuum cleaners. Journal of
Occupational and Environmental Hygiene, 2009. 6(6): p. 374-384.
13.
Flanagan. M.E., Seixas.N., Majar. M., Camp. J., Morgan. M., Silica Dust Exposures
During Selected Construction Activities. AIHA Journal, 2003. 64(3): p. 319-328.
16 14.
Ojima. J., Efficiency of a Tool Mounted LEV System for Controlling Dust Exposures
During Metal Grinding Operations. Industrial Health, 2007. 45: p. 817-819.
15.
Akbar-Khanzadeh. F., Milz.S.A., Wagner. C.D., Bisesi. M.S., Ames. A.L., Khuder. S.,
Susi. P., Akbar-Khanzadeh. M., Effectiveness of Dust Control Methods for Crytalloine
Silica and Respirable Suspended Particulate Matter Exposure During Manual Concrete
Surface Grinding. Journal of Occupational and Environmental Hygiene, 2010. 7(12): p.
700-711.
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Echt. A., Sieber.W.K., Control of Silica Exposure from Hand Tools in Construction:
Grinding Concrete. Applied Occupational and Environmental Hygiene, 2002. 17(7): p.
457-461.
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Shepherd. S., Woskie.S.R., Case Study to Identify Barriers and Incentives to
Implementing an Engineering Control for Concrete Grinding Dust. Journal of
Construction Engineering and Management, 2010. 136(11): p. 1238-1248.
18.
Akbar-Khanzadeh. F., Brillhart.R.L., Respirable Crystalline Silica Dust Exposure
During Concrete Finishing (Grinding) Using Hand-held Grinders in the Construction
Industry. Ann. Occup. Hyg., 2002. 46(3): p. 341-346.
19. Akbar-Khanzadeh. F., Milz.S.A., Ames. A., Susi. P.P., Bisesi. M., Khuder. S.A.,
Akbar-Khanzadeh. M., Crystalline Silica Dust and Respirable Particulate Matter
During Indoor Concrete Grinding - Wet Grinding and Ventilated Grinding Compared
with Conventional Grinding. Journal of Occupational and Environmental Hygiene,
2007. 4(10): p. 770-779.
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Thorpe. A., Ritchie.S.A., Gibson. M.J., Brown. R.C., Measurement of the Effectiveness
of Dust Control on Cut-off Saws Used in the Construction Industry. Ann. Occup. Hyg.,
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21.
Sheehy. J.W., Garcia.A., Echt. A., In-Depth Survey Report of a Demonstration and
Evaluation of Roofing Tile Saws and Cutters Controlling Respirable and Crystalline
Silica Dust, in In-depth Survey Reports, C. NIOSH, Editor. 2006, NIOSH: Cincinnati.
p. 21.
22.
Carlo. R.V., Sheehy.J., Feng. H.A., Sieber. W.K., Laboratory Evaluation to Reduce
RCS Dust When Cutting Concrete Roofing Tiles Using a Masonry Saw. Journal of
Occupational and Environmental Hygiene, 2010. 7(4): p. 245-251.
23.
Shepherd. S., Woskie.S.R., Holcroft. C., Ellenbecker. M., Reducing Silica and Dust
Exposures in Construction During the Use of Powered Concrete Cutting Hand Tools:
Efficacy of LEV on Hammer Drills. Journal of Occupational and Environmental
Hygiene, 201*. 6(1): p. 42-51.
24.
NIOSH, C., Hazard Controls of Drywall Sanding Dust Exposures. Applied
Occupational and Environmental Hygiene, 2000. 15(11): p. 820-821.
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Young-Corbett. D.E., Nussbaum.M.A., Dust Control Efficiency of Drywall Sanding
Tools. Journal of Occupational and Environmental Hygiene, 2009. 6(7): p. 385-389.
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Potts. J.D., Reed.W.R. Horizontal Air Blocking Shelf Reduces Dust Leakage From
Surface Drill Shroud. in SME Annual Meeting and Exhibit. 2009: Society for Mining,
Metalurgy and Exploration Inc.
17 27.
Reed.W.R., Potts.J.D., Improved Drill Shroud Capture of Respirable Dust Utilizing Air
Nozzles Beneath the Drill Deck, in Tanscript Society Minerals Metal Exploration. 2010.
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Pocock, D., Saunders, C.J., Carter, G., Effective control of gas shielded arc welding
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Kluger. N, Kraus.J.W.-K., Musanke. U, Evaluation of Dust Emission Properties for
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31.
Flynn. M.R., Susi.P., Engineering Controls for Selected Silica and Dust Exposures in
the Construction Industry - A Review. Applied Occupational and Environmental
Hygiene, 2003. 18(4): p. 268-277.
18 6. APPENDIX I – ON-TOOL CONTROLS USED IN STUDIES REVIEWED Tools with controls used in reviewed papers
1
Tool
Grinder
Make
Metabo1
Grinder
Grinder
Grinder
Grinder shroud
Grinder shroud
Grinder Shroud
Grinder shroud
Tuckpointing
grinder
Roofing saw
Metabo
Bosch2
Milwaukee3
Pearl4
Transmatic5
Sawtec6
Sawtec
Bosch
Roofing saw
Roofing saw
Roofing saw
Tile saw
Grinder
Grinder
Partner
Revelation
Bronco
Hytile
Matabo7
Sawtec
Bosch
Metowerke GmbH; Nurtingen, Germany
Robert Bosch GmbH; Stuttgart, Germany
3
Milwaukee Electric Tool Corp.; Brookfield, Wisconsin, USA
4
Pearl Abrasive Co.; Commerce, CA, USA
5
Transmatic Inc.; Wilmington, NC, USA
6
Sawtec; Oklahoma City, OK, USA
7
Matabo Vollwellenen, Germany
2
Model
W7-115 Quick 10000
rpm
11025
1347A
6153-20
Vacugaurd
Dustcontrol
Full-dust shroud
Cut (edging) shroud
Dust Director 1775E
Task
1364 Hand held electric
saw
Gasoline powered saw
Tile cutting
Water backpack saw
Manual tile cutter
Tuckpointing grinder
Hiltzx DC500b
Paper
Workplace Solutions: Control of
Hazardous Dust When Grinding
Concrete; NIOSH
Tile cutting
Tile cutting
Tile cutting
Tile cutting
Tuck-pointing
Tuck-pointing
Workplace Solutions: Control of
Hazardous Dust During Tuckpointing;
NIOSH
In-depth survey report of a
demonstration and evaluation of roofing
tile saws and cutters controlling
respirable and crystalline silica dust.,
317-11a Sheehy, Garcia, Echt,
In-depth survey report ECTB 247-12
Heitbrink W.A February 2000
Masonry saw
Right angle
grinder
Mortar rake and
shroud
Angle Grinder
Grinder shroud
Grinder Shroud
Grinder Shroud
Floor standing
20” disc sander
Homemade LEV
for above
Grinder
Grinder
Grinder shroud
Vacuum cleaner
Rotary hammer
drill
Ring hood for
drill
Bellows hood
for drill
Vacuum cleaner
EDCO8
Metabo
EDCO GMS 10
11025
American Tool
Company9
Milwaukee
Zantech Inc10
Dustcontrol11
Workshop made
Fireline12
Brick cutting
Tuck Pointing
In-depth study report EPHB 247-18
Heitbrink. W.A., Watkins. D.S.,
Tuck Pointing
6153-20
Tuck Pointing
Tuck Pointing
Tuck Pointing
Tuck Pointing
Sanding and polishing of
refractory ceramic fibre parts
Sanding and polishing of
refractory ceramic fibre parts
Concrete surface grinding
Concrete surface grinding
Concrete surface grinding
Vacuum source for above
Fireline
Metabo
Bosch
Pearl Abrasive
Dustcontrol
W7-115 Quick
1347A
Vacu-Guard
DC 2700C
Bosch13
Bosch
11221 DVS 7/8” SDSplus 6.9 amp
Part No. 1618190009
Tiger-Vac14
Bellows hood
Drilling and concrete
finishing
Drilling and finishing
concrete
Drilling and finising concrete
Porter-Cable15
#7812
Vacuum source
8
Equipment Development Company, Frederick, Maryland, USA
Ameican Tool Company, Lincoln, Nebraska, USA
10
Zantech Inc. Wayne, New Jersey, USA
11
Dustcontrol. Wilmington, Delaware, USA
12
Fireline Inc. Youngstown, Ohio, USA
13
S-B Power Tool Co., Chicago Ill, USA
14
Plattsburgh NY, USA
15
Porter-Cable, Jackson, Tennessee
9
20
In depth study report EPHB 246-11a.
Dunn. K.H., Shulman. S.A., Cecala.
A.B.
In-depth surver report EPHB 247-15c
Echt. A., Sieber. W.K.,
Also reported in
Echt. A., Sieber. W.K., Control of silica
exposure from hand tools in
construction: App. Occ. Env. Hyg 17(7),
pp 457-461, 2002
Shepherd. S., Woskie. S.R., Holcroft.
C., Ellenbecker. M. (2008): Reducing
silica dust exposures in Construction….
Vacuum cleaner
Grinder
Dustcontrol11
Makita16
#DC3700C
17.5” GA7001L
Grinder
4.5” 2750G
Grinder
Black and
Decker17
Hilti18
Vacuum cleaner
Grinder
Hilti
Metabo
Vacuum
Angle Grinder
Industrial
Contractors’
Supplies19
Dewalt
VCD 50L
5” diamond blade with
shroud
Dust Director High
Power Vacuum
Vacuum
Rigid?
Disc sander
Oliver
Abrasive cutting
tool
Bosch
Dust extraction
guard for above
Vacuum source
for above
Bosch
1364 12 Inch cutter
with all-purpose
diamond blade
Model 1605510215
Bosch
3931 Airsweep (HEPA)
Vacuum source
Wet-Concrete surface
grinding
Concrete surface grinding
6” DG 150
LEV-concrete surface
grinding
Vacuum source for above
Tuckpointing
Vacuum source for above
Akbar-Khanzadeh et al Crystalline silica
dust and RPM during indoor concrete
grinding J.Occ.Env.Hyg
Yasui. S., Susi. P., McClean. M, Flynn.
M., Assessment of Silica Exposure and
Engineering Controls During
Tuckpointing: App. Occ. Env. Hyg, 18,
p. 977-984, (2003)
Tuckpointing
Tungsten Carbide
tipped mortar ra ke20
Wet and dry 8 gallon
shopvac
Model 30
Vacuum source for above
16
Makita, Anjo, Japan
Black & Decker, Towson, Maryland, USA
18
Hilti, Schaan, Liechtenstein
19
Industrial Contractors’ Supplies, North Huntingdon, PA, USA
20
Joran Bor, Randers, Denmark
17
21
Wood sanding
Hampl. V., Johnston. O.E., (1991):
Control of wood dust from disc sanders,
App. Occ. Env. Hyg. 6(11), pp. 938-944
Block and brick cutting
Meeker. J.D., et al (2009)
Engineering control technologies to
reduce occupational silica
exposures in masonry cutting and
tuckpointing. Public Health
Reports, 2009 Supplement Volume
124 pp 101 – 111
Wet masonry
saw
Wet masonry
saw
Tuckpopint
grinder
Grinder shroud
Felker21
Block cutting
Target22
Mason Mate II 14”
diamond blade
Portasaw PS1141S
Bosch
1775E 5”
Mortar removal
Bosch
TG500 and vacuum
adaptor VAC002
WE14-125 Plus
Dust Director Shroud
Same vacuum source as
above
Mortar removal
LEV hood for above
Concrete grinding
Concrete grinding
Concrete grinding
Concrete grinding
Vacuum for above tools
Vacuum for above tools
Dry wall sanding
Tuck pointing
Surface grinding
Block and brick cutting
Angle grinder
Angle grinder
Angle grinder
Concrete grinder
Metabo23
Industrial
Contractors
Supplies24
Metabo1
Metabo1
Metabo1
Eibenstock25
Vacuum
Dustcontrol11
Vacuum
Vacuum
Powered dry
wall sander
Angle Grinder
Flat Grinder
Masonry Saw
Eibenstock25
Shop-vac26
Porter Cable27
W7-115 Quick
WE14-150 Quick
W23-180
EBS 1801 with integral
dust shroud
DC 2800c cyclone
HEPA
Eibenstock 1500
85L575
Model 7800
Porter Cable
Porter Cable
EDCO
F1509 FR
LD 1509 FR
GMS-10
Grinder
Grinder shroud
21
Felker Products Inc., Olathe, Kansas
Target (Now Husqvarna)., Olathe, Kansas
23
Metabo Corp., West Chester, PA
24
Industrial Contractors Supplies Inc. Huntingdon, PA
25
Elekrowerkzeuge GmbH, Eibenstock, Germany
26
Shop-vac Corporation., Williamsport, PA
27
Porter Cable Inc., Cleveland, Ohio
22
22
Akbar-Khanzadeh et al.
Effectiveness of dust control
methods for crystalline silica and
respirable suspended particulate
matter exposure during manual
concrete surface grinding
Vacuum for above tools
Young-Corbett. D.E., et al Dust Control
Effectiveness of Drywall Sanding Tools
Croteau. G.A., et al, The effect
of lev controls on dust
exposures during concrete
Hand-held saw
Vacuum
Partner
Dust Control28
K650 Active
3700c
Surface grinder
Dust collector
Hitachi Koki29
Hitachi Koki
G10SM2
R30Y3
Block cutting
Vacuum source for above
tools
Surface metal grinding
Vacuum source for above
Grinder
Grinder
Grinder shroud
Grinder shroud
Grinder shroud
Vacuum
Masonry saw
Dust hood
Flex30
Metabo
Flex
Sawtec31
Sawtec
Dust Control
EDCO33
EDCO
LD 1509 FR
WE 9-125 Quick
Rigid rubber shroud
Polyurethane shroud
Cut-shroud32
2700C
GMS-14
40320
Concrete surface grinding
Concrete surface grinding
Concrete surface grinding
Concrete surface grinding
Concrete surface grinding
Vacuum for above
Tile cutting
Tile cutting
28
Dust Control, Norsburg, Sweden
Hitachi Koki Co. Ltd., Japan
30
Flex, Steinheim, Germany
31
Sawtec, Costa Mesa, California
32
Modified by cutting section off of front of shroud
33
EDCO Inc., Frederick, Md
29
23
cutting and grinding activities.
AIHA Journal 63(4): pp 458­
467
Ojima. J., Efficiency of a tool mounted
LEV system for controlling dust
exposure during metal grinding
operations. Industrial Health, 45 pp.
817-819
Croteau et al The efficacy of
LEV for controlling dust
exposures during concrete
surface grinding. Ann. Occ.
Hyg. 48(6) p. 509-518, 2004
Carlo. R.V., et al Laboratory evaluation
to reduce RCS dust when cutting
concrete roofing tiles using a masonry
saw. J. Occ. Env. Hyg. 7(4) p 245-251,
2010
Published by the Health and Safety Executive
06/12
Health and Safety
Executive
On-tool controls to reduce exposure to
respirable dusts in the construction industry
A review
Many processes in the construction industry create
large quantities of dust; often materials used in
construction contain silica. If the dust emissions
from these processes are not controlled they
can cause exposures that exceed UK workplace
exposure limits and consequently lead to
occupational diseases such as cancer, silicosis,
chronic obstructive pulmonary disease and asthma.
A common way to control these hazards is to
apply local exhaust ventilation (LEV). However,
construction sites tend be temporary workplaces,
which makes the application of traditional LEV
difficult. One solution is to affix LEV to the tool
being used or to use another mobile form of on-tool
control such as water suppression.
The objective of this project was to conduct a review
of the literature on the subject of the effectiveness of
on-tool controls and to summarise this information for
HSE. The main findings were that:
g
On-tool LEV is capable of reducing exposures by
90% or more.
g
Important factors in achieving this reduction is
hood design and choice of vacuum extraction
source.
g
Even with exposure reductions of 90 %, on-tool
controls never completely eliminated exposure.
This may mean that the use of supplementary
respiratory protective equipment (RPE) is required,
especially where materials contained silica.
This report and the work it describes were funded
by the Health and Safety Executive (HSE). Its
contents, including any opinions and/or conclusions
expressed, are those of the authors alone and do
not necessarily reflect HSE policy.
RR926
www.hse.gov.uk
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