A New Method to Clean Dust From Soiled Work Clothes 

Objective 

 To develop a quick, safe, and effective method that allows 

workers at mineral processing operations to clean their dustsoiled clothing periodically throughout the workday. 

Background 

 Reducing workers' respirable dust exposure to silica and 

other harmful dusts and contaminants is an ongoing goal in the 

U.S. mining industry. One area of known worker exposure is 

from contaminated work clothes. A U.S. Bureau of Mines report 

documented a number of cases where a tenfold increase in a 

worker's dust exposure was measured from contaminated work 

clothes. In these cases, the dust emitted from clothing caused 

the worker's dust exposure to exceed the permissible exposure 

limit in less than 2 hours. The most effective way to eliminate 

this dust source is to have workers clean or change their work 

clothes. 

 There are two federal regulations that impact the clothescleaning process. The first states that at no time shall 

compressed air be directed toward a person, but that when 

compressed air is used, then all necessary precautions shall be 

taken to protect persons from injury. The second regulation 

states that compressed air should only be used for cleaning 

purposes when it is less than 30 psi and used along with personal 

protective equipment. For the mining industry, by default, the 

only approved method to perform clothes cleaning is to have 

workers vacuum their clothes using a HEPA filter system. This 

is very difficult and time-consuming and, in most instances, not 

very effective. Most workers would prefer to use a single 

compressed air hose to blow dust from their work clothes. 

However, not only is this method prohibited by law, it usually 

creates a significant dust cloud in the work environment and 

contaminates coworkers. 

Approach 

 The clothes-cleaning process was designed within the 

guidelines of the two federal regulations and provides a much 

more effective and quicker method for cleaning dust-soiled work 

clothes. The system consists of four main parts: (1) a cleaning 

booth, (2) an air reservoir, (3) an air spray manifold, and (4) an 

exhaust ventilation system. The base dimension of the cleaning 

booth is 48 by 42 inches. This gives the worker enough space to 

rotate in front of the air nozzles to perform the cleaning process. 

Intake air enters the booth through an open grate above the door. 

It then flows down through the booth and exits on the bottom 

back wall. An air plenum at the bottom back wall location 

connects the booth to ductwork that leads to a baghouse dust 

collector. 

 The air reservoir supplies the required air volume to the air 

nozzles used in the spray manifold. Either a 120- or 240-gallon 

reservoir should be used with this system. If it is intended that 

multiple individuals use the clothes-cleaning process one after 

another, then the 240-gallon reservoir should be used. This 

reservoir should be pressurized to 150 psi, located close to the 

cleaning booth, and hard-piped to the air spray manifold located 

in the booth. The air pressure is regulated to 30 psi before being 

directed toward the individual for the clothes cleaning. 

The air spray manifold is composed of 26 spray nozzles 

spaced 2 inches apart (Figure 1). The bottom nozzle is located 

6 inches from the floor and is a circular designed nozzle for 

cleaning the person's work boots. This nozzle is used in 

conjunction with an adjustable ball-type fitting so that it can be 

directed downward. The other 25 air spray nozzles are flat fan 

sprays, which lab testing proved to be most effective cleaning at 

close distances. The 26 air spray nozzles deliver slightly less 

than 500 ft3

/min of air. The average cleaning time with this new 

clothes-cleaning technique during field testing was about 

18 seconds. With the 120-gallon reservoir, there is approximately 22 seconds of air capacity. The 240-gallon reservoir 

doubles the cleaning capacity and should allow for multiple 

workers to clean their clothing, one after another. 

 The exhaust ventilation system is connected to the cleaning 

booth and is capable of creating negative pressure in the booth at 

all times. This ensures that all of the dust removed from a 

worker's soiled work clothes is contained within the cleaning 

booth before being exhausted 

 All workers using this cleaning process are required to wear 

a half-mask, fit-tested respirator with an N100 filter, hearing 

protection, and full-seal goggles. The air spray manifold was 

designed for a 5'10" tall individual, which represents a 50thNo. 509 May 2005 
Figure 1.—Air spray manifold with 26 nozzles spaced 2 inches apart.

percentile male worker. When the person is shorter, the top air 

nozzles can be covered with deflectors to prevent the air sprays 

from directly hitting the individual's face. These deflectors were 

made from 4-in PVC pipe that was cut in half and then into 2-inwide strips. Latches were attached on both sides of these 

deflectors so they could be locked in either the open or closed 

position. 

 This clothes-cleaning system was developed under a 

cooperative research effort between Unimin Corp. and NIOSH. 

All field testing was done at Unimin's operation in Marston, NC. 

Field Testing 

 The mineral processing plant where this clothes-cleaning 

process was field tested had a baghouse with excess capacity. 

During field testing, the baghouse provided an exhaust air 

volume of 4,400 ft3

/min, creating a negative static pressure of 

0.16-in water gauge in the cleaning booth. In lieu of excess 

baghouse capacity, it is estimated that the minimal exhaust air 

volume required for this system would be about 1,000 ft3

/min, 

but further testing is needed to verify this value. 

 During field testing, the new clothes-cleaning process with 

its air spray manifold was compared to the vacuuming system 

and the single handheld compressed air hose. For this testing, 

100% cotton and cotton/polyester blend coveralls were each 

tested by soiling the coveralls with limestone dust. Table 1 

shows the cleaning times and effectiveness of the three different 

techniques. Clearly, the new NIOSH system was much more 

effective than the other two techniques and at a fraction of the 

time. Table 1 also shows that the polyester/cotton blend 

coveralls were cleaned more effectively than the 100% cotton 

type. 

Table 1.—Amount of dust remaining on coveralls after cleaning, 

and cleaning time for cotton and polyester/cotton blend coveralls

Cotton Polyester/cotton blend

Cleaning method 

Dust 

remaining 

on coveralls, 

grams

Cleaning 

time, 

sec

Dust 

remaining 

on coveralls,

grams

Cleaning 

time, 

sec

Vacuuming. . . . . 63.1 398 45.5 346

Air hose . . . . . . . . 68.8 183 48.4 173

New NIOSH system 42.3 17 21.9 18

Summary

 The new NIOSH-developed clothes-cleaning process has 

been shown to be much more effective in removing dust from a 

worker's clothes than the methods currently used by workers. 

This process uses a compressed air nozzle manifold to blow dust 

from the worker's clothes in an enclosed booth. Since the air 

exhausted by the dust collector causes the booth to be under 

negative pressure, no dust escapes to contaminate the work 

environment or other workers. Test results showed that the 

NIOSH process cleaned the work clothes 10 times faster and 

removed up to 50% more dust than the single air hose or 

vacuuming methods. The average cleaning time with the 

NIOSH technique was less than 20 seconds. The cost of this 

clothes-cleaning system was approximately $3,000, excluding 

the cost of the exhaust ventilation component. 

For More Information

For more information about the new NIOSH clothescleaning system, contact Andrew B. Cecala or Douglas E. 

Pollock, NIOSH Pittsburgh Research Laboratory, Cochrans Mill 

Rd., P.O. Box 18070, Pittsburgh, PA 15236–0070; phone: 

412–386–6677 or 412–386–6863, respectively; fax: 412–386–

4917; e-mail: ACecala@cdc.gov or DEPollock@cdc.gov, 

respectively. 

DHHS (NIOSH) Publication No. 2005–136

To receive other information about occupational safety and 

health topics, call 1–800–35–NIOSH (1–800–356–4674), or 

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

Mention of any company name or product does not constitute 

endorsement by the National Institute for Occupational Safety 

and Health.