Engineering Controls for Silica in Construction
Cut-off saws (also known as hand-held abrasive cutters, chop
saws, and quickie saws) are used extensively throughout the
construction industry.They are frequently used without dust
controls to cut brick, concrete slabs, block and pavers which
typically contain crystalline silica. Cutting those masonry
materials without dust controls can surround the worker in a cloud
of dust that contains respirable crystalline silica (RCS).
The Cut-off Saw without Engineering Controls video shows the
potential exposure that results when cutting a concrete block
without dust controls.The workerâ€™s respirable dust exposure is
shown in the bar at the right.The units are milligrams of
respirable dust per cubic meter of air.
Two types of engineering controls are available to reduce dust
exposures from cutting masonry with a cut-off saw.The first type of
control uses water to suppress the dust.The second used local
exhaust ventilation to capture dust at its source.Both types of
control are described below.Each description is followed by a video
that demonstrates the effectiveness of the dust control.
1. Dust suppression with water
Water may be used to suppress dust produced by pneumatic,
hydraulic, or gasoline-powered saws.Water is typically applied to
the blade through one or two nozzles to suppress dust
emissions.Water may be supplied from a portable pressurized tank or
a hose.The recommended flow rate is 0.5 liters (17 ounces) of water
per minute to suppress dust .Less water will
not be as effective.More water will not increase dust
control.Electric-powered saws with water attachments are also
The Cut-off Saw with Water Controls video shows the same worker
using a cut-off saw with dust suppression with water.The workerâ€™s
respirable dust exposure, shown in the bar at the right, is much
lower than in the previous video.
2. Local exhaust ventilation
Local exhaust ventilation is used on hand-held concrete saws in
the form of an exhaust hood (or shroud) that surrounds the
blade.The hood is connected to an industrial vacuum cleaner by a
flexible hose.The vacuum cleaner produces suction to capture the
dust at its source. The hood should be in close contact with the
surface to be cut for best results.Adjustable hoods that can
accommodate different cutting depths are preferred.
The vacuum cleaner should have the following features:
- Sufficient flow rate to capture the dust and transport it to
the vacuum source. One study showed that and air flow rate of 70
cubic feet per minute (cfm) was required to achieve effective dust
- A high-efficiency particulate air (HEPA) filter to reduce the
chances of releasing dust containing RCS from the vacuum into the
- A pre-filter or cyclone to increase the length of service of
the HEPA filter.
- A filter replacement indicator, such as a pressure gauge. If
the vacuum cleaner does not have a pressure gauge, workers can
monitor the air flow by checking to see if a dust plume is escaping
from around the shroud.
- The ability to clean and replace filters and full collection
bowls or bags without exposing the operators to dust.
- A motor that draws at least 10 amps.
A 2-inch diameter hose with a smooth interior and a length of no
more than 15 feet provides adequate air flow to capture and
transport the dust. The hose should have as few elbows or turns as
The Cut-off Saw with Vacuum Controls video shows the worker
using a cut-off saw with local exhaust ventilation.The bar on the
right shows that the workerâ€™s respirable dust exposure is even
lower when compared to the dust suppression with water method.
For more information about dust controls for cut-off saws
of the effectiveness of dust control on cut-off saws used in the
construction industry [PDF – 314 KB]
effect of local exhaust ventilation controls on dust exposures
during concrete cutting and grinding activities [PDF – 354
American Industrial Hygiene Association Journal: 2002 / 63:
Engineering control technologies to reduce occupational silica
exposures in masonry cutting and tuckpointing [PDF – 2.90
Public Health Reports: 2009/ 124 (Supplement 1) 101-111.
Laboratory evaluation to reduce respirable crystalline silica dust
when cutting concrete roofing tiles using a masonry saw [PDF –
Journal of Occupational and Environmental Hygiene:2010/ 7(4):
- Time to
clear the air – paving the way for healthier work
(Press Release) Health and Safety Executive (HSE) 2009.
- Time to Clean
the Air! Protect your lungs when using cut-off saws [PDF – 213
Health and Safety Executive (HSE) (2008).
In-depth survey of dust control technology for cutting concrete
block and tuckpointing brick at The International Masonry Institute
Bordentown Training Center, Bordentown, New Jersey
NIOSH Report No. EPHB 282-13 (2007).
Shepherd & Susan Woskie (2013): Controlling Dust from Concrete
Journal of Occupational and Environmental Hygiene, 10:2, 64-70
Middaugh, Bryan Hubbard, Neil Zimmerman & James McGlothlin
(2012): Evaluation of Cut-Off Saw Exposure Control Methods for
Respirable Dust and Crystalline Silica in Roadway
Journal of Occupational and Environmental Hygiene, 9:3,
controls to reduce exposure to respirable dusts in the construction