No. 487 March 2001

Sweeping Compound Application Reduces Dust From

Soiled Floors Within Enclosed Operator Cabs

Objective

To reduce dust generated from soiled floors within enclosed

operator cabs.

Background

Enclosed operator cabs are widely used on mobile excavation

equipment in the mining and construction industries. They protect

the operator from bad weather, noise, and airborne dusts. The inside

cab environment usually must be kept at very low dust concentrations because of quartz dust generated from the excavation of silicabearing rock. For cabs to be effective in controlling airborne

respirable dust, they must have an efficient air filtration system,

while providing a positive pressurization of the cab interior. Ideally,

the recirculated and exterior makeup air filtration should provide at

least 99% capture efficiency for dust particles as small as 0.3-μm

aerodynamic diameters.

Many of these enclosed cabs use heating units mounted or

directed along the floor (see figure 1), which can cause dust

entrainment problems. Prior studies by the National Institute for

Occupational Safety and Health (NIOSH) of enclosed cabs have

shown that these floor heaters can generate notable amounts of dust

within the cab enclosure (see Technology News 486). Multiple-shift

dust levels measured inside a drill cab increased on average from

0.04 mg/m3

 during the summer months to 0.68 mg/m3 during the

winter months. Additional dust level measurements, made with

optical particle counters during a nondrilling time period, verified

that dust levels inside the cab increased from 0.03 to 0.26 mg/m3

when the floor heater/fan was turned on. Dust levels within the cab

also became greater than the ambient air dust levels outside of the

cab when the floor heater was turned on during the nondrilling time

period. This shows that the floor heater was a notable dust source

problem.

Cab floors are commonly soiled from operators tracking dirt

inside the cab upon entering from the mine or construction site.

Interior cab dust levels can be increased by (1) airflow disturbance

of the soiled floor or (2) operator disturbance of the soiled floor.

Approach

During prior NIOSH surveys of surface coal mine drills, several

drills with very low cab dust levels (#0.1 mg/m3

) were observed to

have floor sweeping compound spread out over the cab floor during

the working shift. This initial observation led to a more controlled

A-B study of the effect of the sweeping compound on the interior cab

dust levels. This study involved dust sampling with and without

sweeping compound inside the cabs of a bulldozer and two drills.

Sweeping compounds commonly use sawdust or cellulose as the

main bulk material, with oil or wax added for dust adhesion purposes.

Sand is sometimes added to increase bulk density. Sweeping

compounds with sand are commonly used to sweep up concrete

floors. Those without sand (usually referred to as "gritless") are used

to sweep up smooth finished floors. Most of the oils and waxes used

for the adhesive ingredient are petroleum-base and can have an

irritating odor. People sensitized to petroleum distillates could have

allergic reactions to these sweeping compounds. A few companies

offer nonpetroleum-base sweeping compounds, using either a natural

oil or chemical additive for dust adhesion. 

During this study, it was decided that only the gritless sweeping

compound (without sand) would be used, eliminating the addition of

another potential silica source inside the cab. Since the sweeping

compound would be applied on the enclosed cab floor for the

duration of the shift, it was decided to use a canola oil-base sweeping

compound to eliminate irritating odor from the petroleum-base

sweeping compounds. The natural canola oil-base sweeping

compound had a slight woody scent.

The three pieces of equipment used in this study had notably

different cab layouts. The bulldozer had a small cab with vents

discharging air-conditioned or heated air from adjustable louvers

at operator waist level and floor level. The bulldozer also had a cloth

fabric seat and a carpeted floor. Drill A had a large cab with the heat

directed from adjustable louvers at operator knee level and the airconditioned air directed from cabin ceiling louvers. This drill had a

vinyl fabric seat and a steel plate floor. Drill B had a small cabin with

the heat directed across the floor (see figure 1) and the airconditioned air directed down from the ceiling. It had a vinyl fabric

seat and a worn rubber mat on a steel floor.
 Figure 1.—Sweeping compound applied on drill cab floor with

floor heater.

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Dozer

Drill A

Drill B

Sweep Compound

Baseline

INSIDE CAB DUST LEVELS, mg/m3

 Figure 2.—Interior cab dust levels measured during

sweep compound study.

Outside dust levels

16%

Unexplained

34%

Sweeping compound

10%

Cab interior design

18%

Combined cab-compound effect

22%

 Figure 3.—The statistical effect of field variables on interior cab dust

levels.

During the operation of each piece of equipment, airborne

respirable dust sampling was done inside and outside the environmental cabs, with and without the sweeping compound applied

to the floor. Three to five shifts of dust sampling were done for each

test condition (baseline and sweeping compound). A 0.25- to 0.5-inthick layer of canola oil sweeping compound was applied on the

floor of the cabs (see figure 1). The average dust levels measured

inside the cabs for these field tests are shown in figure 2. These

average results show that the sweeping compound effectively

reduced dust levels in the two drill cabs, but had no beneficial effect

on the bulldozer cab dust levels. Since the outside cab dust levels

could not be controlled during these field studies and varied

significantly (up to two orders of magnitude), a more thorough

statistical analysis was done to account for the multiple-field

variable effects on the inside cab dust levels.

Figure 3 shows the proportionable effect of the multiple-field

variables on interior cab dust levels. All of the field variables were

found with statistical certainty to have some effect on interior cab

dust levels. The sweeping compound and the interactive cabcompound effects accounted for 32% of the inside cab dust levels.

The cab interior design (such as heater discharge location, floor

type, and seating material) accounted for 18% of the inside cab dust

levels, while the outside dust levels accounted for 16% of the

interior cab dust levels. Thirty-four percent of the remaining interior

cab dust level variations could not be accounted for by these

variables and are unexplained.

From this analysis, it was concluded that the sweeping compound

had a positive effect on suppressing dust from the soiled floor in the

two drill cabs because it was able to make direct contact with and

bind up the dirt on the steel and rubber mat floors. Nearly onequarter (22%) of inside cab dust levels were accounted for by the

combined effect of sweeping compound with respect to the cab

interior design or floor types of the individual cabs tested. Other cab

interior design factors that affect interior cab dust levels are the

heating system discharge locations and the seating materials.

Heating units mounted or directed along the floor can entrain dust

from soiled floors, while soiled cloth seats may release dust from

operator movements.

Recommendations

Application of a gritless (i.e, without sand) natural base sweeping

compound is recommended on smooth enclosed cab floors to help

bind up the dirt and soil tracked into the cabs. The effect of this

control seems to be very beneficial when enclosed cab airflow is

being directed near or at floor level. However, this control method

will only be effective in reducing dust generated from within the

cab. It will not control the dust from poorly designed or poorly

maintained cab enclosures that allow outside dust to enter the cab

through inferior filtration or cab leaks. A natural-base sweeping

compound is strongly suggested for enclosed cab application to

reduce any possible operator irritation or allergic reactions to odors

from petroleum-base oils and wax compounds. Before any of these

sweeping compounds are used, their material safety data sheets

(MSDSs) should be examined for ingredients and precautions.

Finally, good house-keeping is always recommended. The cab

interior should be wiped down periodically, making vinyl seats and

smooth surfaces easier to keep clean.

For More Information

For more information about controlling dust levels in enclosed

cabs, contact John A. Organiscak, Steven J. Page, or Andrew B.

Cecala, NIOSH Pittsburgh Research Laboratory, Cochrans Mill

Rd., P.O. Box 18070, Pittsburgh, PA 15236-0070, phone: (412)

386-6675, (412) 386-6669, or (412) 386-6677, respectively; fax:

(412) 386-4917; e-mail: jdo3@cdc.gov, sep8@cdc.gov, or

aic1@cdc.gov, respectively.

To receive additional information about occupational safety

and health problems, 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.