CONTROL OF SILICA DUST IN CONSTRUCTION 

Small Drivable Milling Machines 

(Less than Half Lane)

Using small drivable milling machines (less than half lane) on asphalt pavement, 

concrete, and other silica- containing materials can generate respirable crystalline 

silica dust. When inhaled, the small particles of silica can irreversibly damage the 

lungs. This fact sheet describes dust controls that can be used to minimize the amount 

of airborne dust when using small drivable milling machines as listed in Table 1 of the 

Respirable Crystalline Silica Standard for Construction, 29 CFR 1926.1153.

Engineering Control Method: Water spray with surfactant (a dust suppressant additive)

Wet Methods

Employers must use spray systems to spray 

a combination of water and surfactants to 

control dust generated by small drivable milling 

machines. These systems use a pump to 

deliver water to the milling surface and to the 

conveyor, where it combines with dust and silica 

particles and reduces airborne levels. The keys 

to effective dust control are (1) water pressure 

and water flow rate; (2) the proper application 

of water amended with a surfactant; (3) nozzle 

location and orientation; (4) the control of droplet 

size; (5) the selection of the best spray pattern 

and spray nozzle type for the operation; and (6) 

the proper maintenance of nozzles and water 

spray application equipment.

Employers are responsible for keeping 

equipment in good condition to minimize dust 

emissions and for training workers on how 

to use the equipment, including ways to limit 

exposure. Focus on the following:

• Maintain an adequate water supply to the

milling machine.

• Rinse or replace water filters according

to manufacturers’ instructions to maintain

water flow.

• Check that hoses are securely connected and

are not cracked or broken.

• Adjust spray nozzles so that water goes to the

drum and the conveyor.

• Check that spray nozzles are not clogged or

damaged.

• Inspect the milling machine and cutting bits

to be sure the machine is in good working

condition.

Indoors or in Enclosed Areas

Using wet methods indoors or in an enclosed 

area may not reliably keep exposure low, so 

extra ventilation or a means of exhaust may be 

needed to reduce visible airborne dust. Extra 

ventilation can be supplied by using:

• Exhaust trunks

• Portable exhaust fans

• Air ducts

• Other means of mechanical ventilation

Photo courtesy of the International Union of Operating Engineers

Small drivable milling machine. 

FactSheet
Ensure that air flow is not impeded by the 

movements of employees during work, or by 

the opening or closing of doors and windows. 

Position the ventilation to move contaminated air 

away from the workers’ breathing zones.

Respiratory Protection

When properly used, wet methods can 

effectively control exposure to silica dust. 

Therefore, Table 1 of the silica standard for 

construction does not require the use of 

respiratory protection when operating small 

drivable milling machines using wet methods.

Additional Information

For more information, visit www.osha.gov/silica

and see the OSHA Fact Sheet on the Crystalline 

Silica Rule for Construction, and the Small Entity 

Compliance Guide for the Respirable Crystalline 

Silica Standard for Construction.

OSHA can provide compliance assistance 

through a variety of programs, including 

technical assistance about effective safety and 

health programs, workplace consultations, 

and training and education. OSHA’s On-Site 

Consultation Program offers free, confidential 

occupational safety and health services 

to small and medium-sized businesses in 

all states and several territories across the 

country, with priority given to high-hazard 

worksites. On-Site consultation services are 

separate from enforcement and do not result 

in penalties or citations. To locate the OSHA 

On-Site Consultation Program nearest you, 

visit www.osha.gov/consultation.

Workers’ Rights

Workers have the right to:

• Working conditions that do not pose a risk of 

serious harm.

• Receive information and training (in a 

language and vocabulary the worker 

understands) about workplace hazards, 

methods to prevent them, and the OSHA 

standards that apply to their workplace.

• Review records of work-related injuries and 

illnesses.

• File a complaint asking OSHA to inspect their 

workplace if they believe there is a serious 

hazard or that their employer is not following 

OSHA’s rules. OSHA will keep all identities 

confidential.

• Exercise their rights under the law without 

retaliation, including reporting an injury or 

raising health and safety concerns with their 

employer or OSHA. If a worker has been 

retaliated against for using their rights, they 

must file a complaint with OSHA as soon as 

possible, but no later than 30 days.

For additional information, see OSHA’s Workers 

page.

How to Contact OSHA

Under the Occupational Safety and Health Act 

of 1970, employers are responsible for providing 

safe and healthful workplaces for their employees. 

OSHA’s role is to ensure these conditions for 

America’s working men and women by setting 

and enforcing standards, and providing training, 

education and assistance. For more information, 

visit www.osha.gov or call OSHA at 1-800-321-

OSHA (6742), TTY 1-877-889-5627.

DSG FS-3933 12/2017

This is one in a series of informational fact sheets highlighting OSHA programs, policies or 

standards. It does not impose any new compliance requirements. For a comprehensive list of 

compliance requirements of OSHA standards or regulations, refer to Title 29 of the Code of Federal 

Regulations. This information will be made available to sensory-impaired individuals upon request. 

The voice phone is (202) 693-1999; teletypewriter (TTY) number: (877) 889-5627.