WORKPLACE SOLUTIONS

From the National Institute for Occupational Safety and Health

Summary

Construction workers are exposed to hazardous dust when 

using handheld electric grinders to smooth poured concrete surfaces after forms are 

stripped. The National Institute for Occupational Safety 

and Health (NIOSH) found 

that exposures could be reduced if a local exhaust ventilation (LEV) shroud was attached to the grinder.

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Control of Hazardous Dust When 

Grinding Concrete

disease, reduced lung function, and 

other disorders [NIOSH 2002a]. 

Workers in the construction industry 

may breathe dust that contains silica 

during various tasks including cutting 

brick and block, tuckpointing masonry, using a jackhammer to break 

concrete or rock, or grinding concrete. A NIOSH [2001] study found 

that workers grinding concrete to 

smooth poured concrete surfaces after forms are stripped were exposed 

from 35 to 55 times the NIOSH recommended exposure limit (REL) for 

airborne dust containing crystalline 

silica. NIOSH evaluated the use of

LEV shrouds on handheld concrete 

grinders to see whether they reduce 

worker exposure to dust [Echt and 

Seiber 2002; NIOSH 2002b].

NIOSH Study

The concrete finishers in the NIOSH 

studies were responsible for smoothing poured concrete walls and columns. The LEV system consisted of a grinder that was equipped 

with a ventilation shroud, a length 

of flexible corrugated hose, and a 

portable electric vacuum cleaner that 

acted as the fan and dust collector 

for the ventilation system (Figures 1 

and 2). The concrete surfaces were 

flat and allowed the shroud to make 

a good seal with the concrete. Four 

commercially available shrouds were 

used in the NIOSH study. All grinder/

shroud combinations reduced dust exposure by at least 90%. 

Description of 

Exposure

Breathing dust that contains crystalline silica can lead to the development of silicosis, a deadly lung disease. No effective treatment exists 

for silicosis, but it can be prevented 

by controlling workers’ exposure to 

dust containing crystalline silica. Exposure to crystalline silica has also 

been linked to lung cancer, kidney 

Figure 1. Grinder in use with the control in place.
Grinders

The grinders used were rated at either 10,000 or 11,000 

rpm: Metabo model W7-115 Quick 10,000-rpm grinder and Metabo model 11025 grinder (Metabowerke 

GmbH; Nürtingen, Germany); Bosch model 1347A 

grinder (Robert Bosch GmbH; Stuttgart, Germany); and 

Milwaukee model 6153–20 grinder (Milwaukee Electric Tool Corp.; Brookfield, WI). The grinders were fitted with 4-inch diameter diamond cup wheels (PW series, Pearl Abrasive Co.; Commerce, CA). 

LEV shrouds

Four LEV shrouds were used in the study. The shrouds 

were selected based on their rugged appearance, how 

easily they could be mounted on the grinders, and their 

availability for purchase. The shrouds used were Vacuguard (Pearl Abrasive Co.; Commerce, CA), Dustcontrol (Transmatic Inc; Wilmington, NC); and “full-dust 

shroud” and “cut (edging) shroud” (Sawtec; Oklahoma 

City, OK).

Vacuum cleaners and hoses

The grinder/shroud pairs were connected via 1.5-inch 

(inside diameter) corrugated flexible hose to two types 

of industrial vacuum cleaners (DC 2700 and DC 3700; 

Dustcontrol AB, Norsborg, Sweden). The manufacturer reports that the DC 2700 vacuum has a maximum 

flow capacity of 112 cubic feet per minute (190 cubic 

meters per hour), and a maximum negative pressure of 

84 inches w.g. (21 kPa). The DC 3700 has a maximum 

flow capacity of 188 cubic feet per minute (320 cubic 

meters per hour) and a negative pressure of 96.5 inches w.g. (24 kPa). 

Controls

NIOSH and its partners have developed recommendations to protect workers from exposure to crystalline silica dust during construction activities [NIOSH 1996; 

Echt and Seiber 2002; NIOSH 2002a; Heitbrink and 

Collingwood 2005]. Some of the benefits of using the 

dust control noted in this report include reducing worker exposure to hazardous dust and potentially allowing 

for use of less protective respiratory protection, reduced 

cleanup time, and reduced cleanup exposures. 

Vacuum cleaners

The choice of a vacuum cleaner depends on the task. It 

must be carefully selected to include features such as the 

following:

 Sufficient flow rate to capture the dust and transport 

it to the vacuum source

 Uses a high-efficiency particulate air (HEPA) filter to 

reduce the chance of releasing dust containing crystalline silica from the vacuum into the worksite

 Uses pre-filter or cyclone to increase the length of 

service of the HEPA filter

 Uses filter replacement indicator

 Filters can be cleaned and replaced or full collection 

bowls or bags can be replaced without exposing the 

operators to dust

The vacuum cleaner should draw at least 10 amps if it is 

used as part of a ventilated grinder system, so it can overcome filter loading. Some vacuum cleaners are equipped 

with a pressure gauge that indicates when the air flow 

rate is too low to be effective. If the vacuum cleaner does 

not have a pressure gauge, workers can monitor the air 

flow by looking at the dust plume. If dust is escaping under the shroud, the dust collected on the pre-filter needs 

to be dislodged or the vacuum cleaner bags or filters need 

to be changed. 

Hose

A 1.5- or 2-inch diameter hose with a relatively smooth 

interior and a length of no more than 15 feet should provide adequate air flow. The hose should have as few elbows or turns as possible. A study on tuckpoint grinders 

[Heitbrink and Collingwood 2005] reported that 2-inch 

diameter hoses provided better air flow than smaller 

(e.g., 1.5 inch) diameter hoses. Dust has a greater tendency to settle in larger diameter hoses and should be 

Figure 2. Diagram of grinder showing main parts. cleared before and after each use.
Shroud

The shroud can be purchased with the grinder, separately, or as a unit with the vacuum cleaner and hose. 

The shroud should totally enclose the spaces around the 

exhaust entry point for the hose. The exhaust shroud 

should have an entry point for the hose matching the diameter of the hose.

Work practices

 Keep the shroud flat against the surface of the concrete while grinding.

 Shake the hose as needed to loosen the settled dust 

and prevent the hose from clogging.

 When using the grinder, look to make sure no dust is 

escaping from the shroud.

 If dust is escaping, turn off the unit and clean or 

change the filter as recommended by the manufacturer. Sometimes the build-up on the filter can be 

dislodged by simply moving or shaking the cleaner, or 

turning the motor off and on a few times. Build-up on 

the filters slows down the air flow through the system 

and reduces dust capture.

 Change vacuum cleaner bags before they leak. 

 When changing filters, bags, or self-contained collection bowls, use proper disposal practices and use respirators if appropriate.

Since NIOSH last investigated concrete grinders in 2002, 

several grinder manufacturers have introduced tools with 

dust controls. Studies since the NIOSH investigation show 

the effectiveness of LEV controls in reducing respirable 

dust when using concrete grinders [Croteau et al. 2004; 

Akbar-Khanzadeh et al. 2007].

Respirators

Workers and employers should be aware of the high risk 

of dust exposure in poorly ventilated areas (such as in 

corners or inside buildings). This may result in increased 

exposure to hazardous dust. 

The dust control cited in this report may greatly reduce 

worker exposure to hazardous dust; however, respirators 

are still necessary to reduce exposure to crystalline silica below the NIOSH REL of 50μg/m3

. Follow the Occupational Safety and Health Administration (OSHA) 

Respiratory Protection Standard (29 CFR* 1910.134) 

(www.osha.gov/SLTC/etools/respiratory/index.html). 

The provisions of the program include procedures for selection, medical evaluation, fit testing, training, use, and 

care of respirators.

*Code of Federal Regulations. See CFR in references.

Acknowledgments

The principal contributors to this publication were Alan 

Echt of the Division of Applied Research and Technology, NIOSH and John J. Whalen under contract with the 

U.S. Public Health Service, Division of Federal Occupational Health. 

References

Akbar-Khanzadeh F, Milz S, Ames A, Susi PP, Bisesi M, Khuder SA, Akbar-Khanzadeh A [2007]. Crystalline silica dust and 

respirable particulate matter during indoor concrete grinding—wet grinding and ventilated grinding compared with 

uncontrolled conventional grinding. Occup. Environ. Hyg 

4:770–779. 

CFR. Code of Federal regulations. Washington, DC: U.S. Gov-ernment Printing Office. Office of the Federal Register. 

Croteau GA, Flanagan ME, Camp JE, Seixas NS [2004]. The 

efficacy of local exhaust ventilation for controlling dust exposures during concrete surface grinding. Ann. Occup. Hyg 

48(6):509–518. 

Echt A, Seiber K [2002]. Control of silica exposure from hand 

tools in construction: grinding concrete. Appl Occup Environ 

Hyg 17(7):457–461. 

Heitbrink WA, Collingwood S [2005]. Protecting tuckpointing workers from silica dust: draft recommendations for a ventilated grinder. The Center to Protect Workers’ Rights, Silver Spring, MD [www.cdc.gov/

elcosh/docs/d0600/d000683/d000683.html].

NIOSH [1996]. NIOSH Alert: Request for assistance in preventing silicosis and deaths in construction workers. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, DHHS 

(NIOSH) Publication No. 96–112.

NIOSH [2001]. In-depth survey report of four sites: exposure 

to silica from hand tools in construction chipping, grinding, 

and hand demolition at Frank Messer and Sons Construction 

Company, Lexington and Newport KY; Columbus and Springfield, OH. Cincinnati, OH: U.S. Department of Health and 

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

Survey Report No. EPHB 247–15. 

NIOSH [2002a]. NIOSH hazard review: Health effects of occupational exposure to respirable crystalline 

silica. 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. 2002–129. 

NIOSH [2002b]. In-depth survey report of control of 

respirable dust and crystalline silica from grinding 

concrete at Messer Construction, Newport, Kentucky and 

Baker Concrete Construction, Dayton, Ohio. Cincinnati, OH: U.S. Department of Health and Human Services, 

Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Survey Report 

No. EPHB 247–21. 
DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

4676 Columbia Parkway

Cincinnati, OH 45226–1998

safer • healthier • peopletm April 2009

For More Information

The information in this document is based on NIOSH field 

studies. More information about silica hazards and controls 

is available on the NIOSH Web site at www.cdc.gov/niosh/

topics/silica/default.html. 

To receive copies of the NIOSH field study reports that 

formed the basis of this document or to obtain information 

about other occupational safety and health topics, contact 

NIOSH at 

Telephone: 1–800–CDC–INFO (1–800–232–4636)

TTY: 1–888–232–6348  E-mail: cdcinfo@cdc.gov

or visit the NIOSH Web site at www.cdc.gov/niosh

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NIOSH eNews by visiting www.cdc.gov/niosh/eNews.

Mention of any company or product does not constitute endorsement by NIOSH. In addition, citations to Web sites external to NIOSH do not constitute NIOSH endorsement of 

the sponsoring organizations or their programs or products. 

Furthermore, NIOSH is not responsible for the content of 

these Web sites. All Web sites addressess referenced in this 

document were accessible as the publication date.

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 work-related 

illness and injuries. All Workplace Solutions are based on research studies that show how worker exposures to hazardous 

agents or activities can be significantly reduced.

Control of Hazardous Dust When Grinding Concrete

DHHS (NIOSH) Publication No. 2009–115