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Engineering Controls and Housekeeping Practices to Reduce Silica Dust Levels

September 26, 2016

OSHA’s new silica dust rule sets very strict standards for exposure — a limit of 50 micrograms of respirable crystalline silica per cubic meter of air, averaged over an eight-hour day. For reference, 50 micrograms has roughly the same mass as a fly’s wing. (If you’re into stats like that, here’s another one: a human eyelash weighs about 75 micrograms.)

The bottom line is that 50 micrograms is not very much. To keep your workers’ exposure below this level, you’ll need to implement both proper engineering controls and housekeeping practices. This article reviews the controls and practices that will help you meet compliance standards for silica dust.

Substitutes

The best way to prevent health problems related to silica dust is to avoid silica altogether. Many silica substitutes are available and appropriate for many applications.

Here are a few of them:

  • Aluminum oxide
  • Shot
  • Glass beads
  • Garnet
  • Emery
  • Urea plastic

The OSHA website provides an extensive list of silica substitutes, along with their recommended applications, advantages and limitations, and price.

Ventilation

You can stop silica dust dispersion before it starts using local exhaust ventilation (LEV). A LEV is essentially a proper vacuum cleaner hooked up to a piece of equipment with a dust shroud. This setup removes the dust at or close to its point of origin so that it doesn’t get the chance to enter workers’ breathable air space.

LEV system

LEV system

LEV systems work particularly well for construction applications with concrete grinders, cut-off saws, and tuck-pointing. They can reduce respirable crystalline silica dust exposure by 5 to 20 times.

Learn more about LEV systems 29 CFR 1926.57: Ventilation.

Dust containment systems

There are several types of dust containment systems. The right one for you depends on the design of your facility, your applications, and your assessed risk, among other factors.

For example, in a large facility where hazardous dust is everywhere, you might consider installing an building-wide dust collection system to continuously remove and filter the contaminated air. If you just have a few machines generate dust, install a dust shroud hooked to a portable dust collector directly on the equipment.

Your hazard and risk assessment will help you identify the specific control points where you should concentrate your efforts.

Wet methods

Dry drilling and cutting may be common practices in construction and other industries. But they aren’t the only game in town. In some cases, wet methods work just as well.

Wet methods involve spraying water (or another liquid agent) on an area before performing a task that generates dust, like drilling or cutting. Obviously, wet work isn’t always possible. For example, you probably want to avoid water if you’re working near electrical equipment.

OSHA provides several industry-specific fact sheets that address wet and dry work methods. Here are two for construction:

Housekeeping

Silica dust can be stubborn. Even if you use proper ventilation, install dust collectors, and employ wet methods when possible, you’ll likely still have dust particles hanging around, just waiting to go airborne at the slightest draft or brush of a broom.

To keep these dust particles firmly under control, you need a housekeeping program. Under the new standard, the only approved housekeeping methods are wet methods (i.e., using water to keep dust down) and vacuuming using equipment that meets strict filter requirements.

Using compressed air, dry brushing, or dry sweeping is prohibited unless wet methods and vacuuming aren’t feasible.

For more more information on housekeeping and the filtration requirements for vacuums and other dust collection equipment, read OSHA’s Silica Dust Rule: How Vacuum Filtration Helps You Protect Your Workers and Stay Compliant.

Personal protective equipment

Personal protective equipment, such as respirators, are an important part of a dust safety program. However, they should be considered something of a last resort.

OSHA has determined that respirators are not as protective, or as practical, as engineering controls. For respirators to work properly, they must be selected for each worker, individually fitted and periodically refitted, and regularly maintained, which includes replacing filters and other parts as necessary. If these procedures aren’t followed, workers will continue to be exposed to silica dust.

Because of their limitations, the new rule specifies that respiratory protection should only be used in cases where engineering controls fail to adequately eliminate or control dust.

For more information, see 29 CFR 1910.134: Respiratory Protection.

Written control plans

Finally, everything needs to be documented. The new rule requires employers to have a written exposure control plan that describes the following:

  • The tasks that could expose workers to silica dust
  • The engineering controls, work practices, and respiratory protection used to limit exposure for each task
  • The housekeeping measures and restricted work area procedures used to limit exposure

Want to learn more about how to reduce exposure to silica dust? Read Silica Dust at a Glance: Answers to 7 FAQ About OSHA’s New Rule.

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