DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Description of 

Exposure

Breathing dust that contains respirable 

crystalline silica can lead to silicosis, 

a deadly lung disease. Respirable dust 

is that fraction of the aerosol that is 

small enough to reach the deeper, 

gas-exchange regions of the lungs. No 

effective treatment exists for silicosis, 

but it can be prevented by controlling 

workers’ exposures to dust containing 

crystalline silica. Exposure to crystalline silica has also been linked to lung 

cancer, kidney disease, reduced lung 

function, and other disorders [NIOSH 

2002]. Crystalline silica is found in 

several construction materials, such 

as brick, block, fiber-cement siding, 

mortar and concrete. Many construction tasks have been associated with 

overexposure to dust containing crystalline silica [Chisholm 1999, Flanagan 

et al. 2003, Rappaport et al. 2003, Qi et 

al. 2013a]. Among these tasks are tuckpointing, concrete cutting, concrete 

grinding, abrasive blasting, and cutting 

fiber-cement siding. 

The use of fiber-cement siding in construction and renovation is undergoing 

rapid growth. From 1991 to 2010, the 

market share of fiber-cement siding has 

climbed from 1% to 13% [U.S. Census 

Bureau 2013]. In contrast, the market 

share of wood siding in residential construction has decreased from 38% to 

8% [U.S. Census Bureau 2013]. The durability and appearance of fiber-cement 

siding, which simulates wood without 

its maintenance issues, is appealing and 

provides a competitive advantage over 

other building materials. The number 

of workers exposed to dust containing 

crystalline silica will likely increase as 

the use of fiber-cement siding displaces 

other siding products [Bousquin 2009]. 

Fiber-cement board is cut using three 

methods: (1) scoring and snapping 

the board, (2) cutting the board using 

shears, and (3) cutting the board using 

a power saw. Although the first two 

methods are relatively dust-free, they 

are not appropriate for use with siding 

mainly because they are slow and not 

very precise [Bosuquin 2009]. 

Fiber-cement products can contain 

as much as 50% crystalline silica and 

cutting this material with a power saw 

has been shown to cause excessive exposures to respirable crystalline silica. 

One study by Lofgren et al. [2004] 

reported that cutters’ uncontrolled exposures to respirable crystalline silica 

ranged between 0.02 to 0.17 milligram 

per cubic meter (mg/m3

), which was up 

to 3.4 times the NIOSH recommended exposure limit (REL) for respirable 

crystalline silica of 0.05 mg/m3

. In an 

in-depth field survey, Qi et al. [2013a] 

reported that a cutter’s uncontrolled 

exposure to respirable crystalline silica 

resulted in an exposure of between 0.02 

to 0.13 mg/m3

, which was up to 2.6 

times the NIOSH REL.

NIOSH Study

Power saws, such as circular saws and 

compound miter saws, are used to cut 

fiber-cement siding. These saws are 

normally used with 4–8 tooth polycrystalline diamond-tipped (PCD) 

blades specifically designed to cut 

fiber-cement siding and minimize dust 

generation. Several commercially available circular saws have dust-collecting 

Reducing Hazardous Dust Exposure 

When Cutting Fiber-Cement Siding

Summary

Construction workers may be exposed to hazardous dust containing 

silica when cutting fiber-cement 

siding. The National Institute for 

Occupational Safety and Health 

(NIOSH) found that workers’ exposures could be reduced by attaching a regular shop vacuum to 

a dust-collecting circular saw providing a simple low-cost solution.
2

features such as hoods and exhaust take-offs that can be connected to vacuum cleaners or dust-collection bags. These 

hoods are designed to partially enclose the saw blade.

NIOSH scientists conducted a study to develop practical 

engineering control recommendations for respirable crystalline silica from cutting fiber-cement siding. The first phase 

of the study to characterize the dust generated from cutting 

fiber-cement siding was conducted in a laboratory setting 

[Qi et al. 2014d]. The three dust-collecting circular saws 

evaluated in this study featured built-in dust collection containers or shrouds that functioned as a hood and partially 

enclosed the saw blade. When fiber-cement siding was cut, 

the air flow induced by the spinning blade caused a large 

portion of the dust generated to be collected in the container or shroud and also directed the dust to an exhaust port, 

which was connected to an external vacuum cleaner. The 

study found that the dust removal efficiency for the circular saws when used in conjunction with the external vacuum 

cleaner, which had a cyclone pre-separator and a high-efficiency particulate air (HEPA) filter cartridge, was greater 

than 81% even at a low air flow rate of 0.83 cubic meters per 

minute (m3

/min) or 29 cubic feet per minute (CFM). It was 

also found that further increasing the flow rate provided by 

the external vacuum cleaner did not substantially improve 

the dust removal efficiency. A regular shop vacuum typically has a flow rate higher than 30 CFM. Thus, the results from 

the laboratory evaluation suggested that connecting a dustcollecting circular saw to a regular shop vacuum can be a 

simple and low-cost engineering solution to control the dust 

generated from cutting fiber-cement siding. 

To further validate the effectiveness of the control, four field 

surveys [Qi et al. 2013b, Qi et al. 2014a, Qi et al. 2014b, 

Qi et al. 2014c] were conducted at locations where fibercement siding was being cut. A regular shop vacuum, which 

had a high efficiency disposable filter bag as a pre-filter and 

a cartridge filter (not HEPA), was used in these surveys. 

The survey results showed that the 10-hour time weighted 

average (TWA) exposure to respirable crystalline silica for 

the workers who mainly cut fiber-cement siding on the job 

sites was controlled to well below the NIOSH REL. These 

findings indicated that the engineering control measure 

evaluated, if used properly, was effective in reducing worker 

exposures to concentrations below the NIOSH REL for respirable crystalline silica. This engineering control measure 

has the potential to provide an effective, simple and low cost 

(comparing to HEPA vacuums) solution for workers cutting 

fiber-cement siding. 

Recommended Controls

LEV System

 Use a shop vacuum with an air-flow rate of about or higher 

than 30 CFM. A vacuum hose can be used to attach the circular saw to the shop vacuum. Figures 1 and 2 depict the 

circular saw with dust collector and how it was connected 

to the shop vacuum during the NIOSH field evaluation.

 The hose that connects the shop vacuum to the saw should 

be of sufficient size (1.25-inch or greater inner diameter) 

to allow adequate airflow for the capture and transport of 

saw dust. To maximize efficiency, the hose should only be 

as long as necessary and be kept as straight as possible.

 A high efficiency disposable filter bag can be used as a prefilter in the shop vacuum to capture most of the dust. This 

will prolong the life of the filter cartridge that captures the 

dust that goes through the filter bag.

 The shop vacuum and the circular saw can be plugged 

into an intelligent vacuum switch. This eliminates the 

distraction for the operator of turning on and off a dust 

collection system and ensures the vacuum is running 

while operating the saw, avoiding uncontrolled dust 

release. The switch also allows for delay in turning off the 

shop vacuum when the saw is turned off, removing the remaining dust in the vacuum hose following the cutting of 

a board. Some shop vacuums have incorporated such an 

intelligent vacuum switch. For those shop vacuums that 

don’t have it, an aftermarket device with the same feature 

can be purchased and utilized [Qi et al. 2013b, Qi et al. 

2014a, Qi et al. 2014b, Qi et al. 2014c]. 

Figure 1. Rear view of a worker bent at the waist 

wearing a helmet while cutting fiber cement boards on 

trestles. He is using a dust collecting circular saw connected to a vacuum. A blue boom lift and red brick 

building are in the background.

Photo by NIOSH
3

Circular Saws

 Use only circular saws with a built-in dust collection 

container or shroud that functions as a hood, partially encloses the saw blade, and can be easily connected to the 

LEV system. 

Circular Saw Blades

 Use polycrystalline diamond-tipped (PCD) blades designed to be used to cut fiber-cement siding. Compared 

to Carbide-tipped blades, they provide a cleaner cut of 

the siding, exhibit a longer wear life, and may reduce the

dust generated. 

Work Practices

 When using a power saw (circular or miter), cut fibercement siding outdoors when practical.

 Avoid cleaning up fugitive fiber-cement dust on job site 

using dry sweeping, and use vacuum instead.

 Provide a covered trash can near the work station for 

saw operators to dispose of collected dust. Follow local, 

state and/or Federal regulations when disposing of fibercement dust.

 Ensure the shop vacuum is maintained according to manufacturer recommendations.

 Ensure the shop vacuum is inspected daily for defects 

(new filter bags and cartridges inspected for holes, cuts, 

etc.) and that filter bag and cartridge filter are changed 

regularly to prevent restricted air flow.

 Do not clean the cartridge filter, work clothing, or other 

areas with compressed air. In addition to creating a hazardous dust cloud, compressed air can damage the filter.

 Inspect the saw blade frequently and change as necessary 

to ensure the blade is not excessively worn.

 Keep nearby workers clear from any dust generating operation.

 Written procedures should be developed and employees 

trained on the hazards of silica exposure and the proper 

methods to reduce exposure.

Respirators

The dust controls provided in this document may greatly 

reduce worker exposure to hazardous dust; however, NIOSH 

recommends the use of half-facepiece particulate respirators 

with N95 or better filters for airborne exposures to crystalline silica at concentrations less than or equal to 0.5 mg/

m3

 [NIOSH 2008]. Employers should consult with an occupational safety and health professional and/or certified 

industrial hygienist to determine the respirator that would 

be best suited for the application. Employers should always 

follow the Occupational Safety and Health Administration 

(OSHA) Respiratory Protection Standard (29 CFR 1910.134) 

if respiratory protection is used. (www.osha.gov/SLTC/

etools/respiratory/index.html). NIOSH guidance for selecting respirators can be found at http://www.cdc.gov/niosh/

docs/2005-100/default.html.

Acknowledgments

This document was prepared by Chaolong Qi, NIOSH 

Division of Applied Research and Technology, and John J. 

Whalen, formerly with NIOSH.

References

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Publication date: February 13, 2009. http://www.ebuild.

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Chisholm J [1999]. Respirable dust and respirable silica 

concentrations from construction activities. Indoor 

Built Environ 8:94–106. http://www.karger.com/Article/

Abstract/24619

Figure 2. A dust collecting circular saw sitting on a blue 

filing cabinet and connected to a shop vacuum that is on 

the floor.

Photo by NIOSH
Flanagan ME, Seixas N, Majar M, Camp J, Morgan M 

[2003]. Silica dust exposures during selected construction 

activities. Am Ind Hyg Assoc J 64:319–328. http://deohs.

washington.edu/sites/default/files/images/general/Majar

Thesid.pdf

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2002-129.pdf

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(NIOSH) Report No. EPHB 358–11a. http://www.cdc.gov/

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surveyreports/pdfs/358-13a.pdf

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(NIOSH) Report No. EPHB 358–14a. http//www.cdc.gov/

niosh/surveyreports/pdfs/358-14a.pdf

Qi C, Kratzer J, Echt A [2014c]. In-Depth Survey Report: 

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(NIOSH) Report No. EPHB 358–15a. http://www.cdc.gov/

niosh/surveyreports/pdfs/358-15a.pdf

Qi C, Echt A, Gressel M [2014d]. Evaluation of the dust generation and engineering control for fiber-cement siding. 

DHHS (NIOSH) Report No. EPHB 358–16a. http://www.

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wallmat.pdf 

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Reducing Hazardous Dust Exposure When Cutting

Fiber-Cement Siding

This document is in the public domain and may be freely 

copied or reprinted. NIOSH encourages all readers of 

the Workplace Solutions to make them available to all 

interested employers and workers.

As part of the Centers for Disease Control and Prevention, 

NIOSH is the Federal agency responsible for conducting 

research and making recommendations to prevent workrelated illnesses and injuries. All Workplace Solutions 

are based on research studies that show how worker 

exposures to hazardous agents or activities can be significantly reduced.

DHHS (NIOSH) Publication No. 2015–185

For More Information

safer • healthier • peopletm June 2015

Suggested Citation

NIOSH [2015]. Reducing hazardous dust exposure when cutting fiber-cement siding. By Qi C, Whalen JJ. Cincinnati, OH: U.S. 

Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational 

Safety and Health. DHHS (NIOSH) Publication No. 2015–185.