All respirators, including filtering facepieces, must be selected based on the hazard and must be certified by NIOSH. If your dust mask does not bear the NIOSH approval label, it can

Clearing the Air About Disposable Dust Masks

Always be sure that you have chosen the correct mask for the application and that you follow all of the manufacturer's recommendations and all OSHA requirements.

The president of Chicago's Trauma Risk Management Research Institute has history with Chernobyl and has invented an "emergency bra," with two cups that can separated and strapped on over the faces of two people to act as air-filtering masks. The RAD EBra model comes with a radiation sensor insert. The manufacturer can also take any bra provided by a customer and perform alterations to turn it into an EBra. This a true bit of trivia; I know because, out of curiosity, I bought one! I've debated about the political correctness of using it for employee respirator training.

I recently presented an OH&S webinar on respiratory protection. Most of the questions asked by attendees related to the application of the OSHA Respiratory Protection Standard, 1910.134, to disposable dust masks, which OSHA calls "filtering facepieces." In 1910.134(b), OSHA includes the following definition: "Filtering facepiece (dust mask) means a negative pressure particulate respirator with a filter as an integral part of the facepiece or with the entire facepiece composed of the filtering medium." 

An OSHA Letter of Interpretation1 dated Nov. 22, 2011, clearly addresses a number of questions regarding filtering facepieces. The bottom line is yes, all of the requirements outlined in the Respiratory Protection Standard do apply to use of these masks if they are required by the employer to protect an employee from any form of dust that exceeds the OSHA Permissible Exposure Limit (PEL)

The only exception is if use is voluntary (Ref 1910.134(c)(2)).

Voluntary Use
When the exposure does not exceed the PEL, dust masks may be made available to employees for voluntary use, or employees may use their own. The decision to permit voluntary use lies with the employer. The only requirements that apply are:

  • The employer must determine that voluntary use does not in itself create a hazard. This would include avoiding reuse of contaminated dust masks and also ensuring proper use by the employee:
  • The employer must provide the voluntary user with Appendix D, Information for Employees Using Respirators When Not Required Under the Standard. This appendix provides four steps that the employee should take to avoid hazards:
    1. Ensure proper use and maintenance per manufacturer's instructions.
    2. Ensure that only NIOSH-certified masks are used, with the proper design for the application.
    3. Ensuring that the exposure does not contain other contaminants that the mask is not designed to protect from, i.e., gases, vapors, or very small particles from fumes or smoke that are smaller than the particle size rating of the dust mask.
    4. Keep track of the respirator to avoid using someone else's.
  • Normally, voluntary use of most respirators requires the employer to implement those parts of their written respiratory protection program that are necessary to ensure the safety of the employee, but there is an exception for voluntary use of filtering facepieces.

Respiratory Protection Requirements for Filtering Facepieces
For filtering facepieces:

  • NIOSH approval: According to OSHA, all respirators, including filtering facepieces, must be selected based on the hazard and must be certified by NIOSH. If your dust mask does not bear the NIOSH approval label, it can't be used for either required or voluntary protection.
  • Written respiratory protection program: If you already have a written program that meets the OSHA requirements for other respirators, be sure to include these in the program, including any site-specific procedures. If you don't have a written program, you will need to develop one, even if your only use is for required disposable dust masks. Refer to 29CFR1910.134(c) for the specific requirements for the program content.
  • Medical evaluations: As with any negative-pressure respirator and half-mask respirator, filtering facepieces can restrict airflow to the user's lungs. Medical evaluations are required to ensure that the user will not be placed at risk when wearing the mask.
  • Fit testing: Fit testing is required for disposable dust masks, however, you may be limited to the type of testing that can be used. There are four types of chemicals used for Qualitative fit testing—Saccharin, Bitrex, Irritant Smoke, and Banana Oil (Isoamyl Acetate). Be sure to check with the manufacturer to see what can be used for your dust mask. (For example, per 3M, only Saccharin and Bitrex can be used for its N95 dust masks.) Quantitative fit testing is also appropriate for dust masks.
  • Training: All of the same training requirements apply. OSHA at 1910.134(k) specifies the training content and frequency. The employer shall ensure that the training is provided to an employee prior to using a respirator, repeated annually. Retraining is required: 1) When changes or respirator types render previous training obsolete, 2) When the employee demonstrates inadequate knowledge or retention of the training, or 3) When any other situation arises making retraining necessary to ensure safe use.

Dust Masks
Training must be comprehensive and understandable. The employer shall also ensure that each employee can demonstrate knowledge of at least the following:

  • Why the respirator is necessary and how improper fit, usage, or maintenance can compromise the protective effect of the respirator.
  • What the limitations and capabilities of the respirator are.
  • How to use the respirator effectively in emergency situations, including situations in which the respirator malfunctions.
  • How to inspect, put on and remove, use, and check the seals of the respirator.
  • What the procedures are for maintenance and storage of the respirator.
  • How to recognize medical signs and symptoms that may limit or prevent the effective use of respirators.

Dust masks are identified by the NIOSH numbers, for example, there are three basic types of dust masks. The differences relate to the presence of oil mist in the atmosphere:

  • N-Series Filters: These are restricted to use in atmospheres that are free from aerosolized oil. They may be used for any solid or liquid airborne particulates that do not contain oil.
  • R-Series Filters: These are intended for removal of any particulates, including oil-based liquid aerosols.
  • P-Series Filters: These are also intended for removal of any particulates, including oil-based liquid aerosols, and may be used for any solid or liquid particulate airborne hazard. In this case, NIOSH requires that respirator manufacturers establish time-use limitations for P-series filters.  Be sure to check the manufacturer specifications for these limits.

All particulate filters and dust masks are rated based on particulate removal efficiency, as shown in this chart:

Assigned Protection Factor (APF)
The APF is the level of respiratory protection that a respirator is expected to provide as long as it is functioning properly and the user is wearing it correctly. The APF indicates the amount that a respirator can be expected to reduce contaminant concentration.

Disposable dust masks have the same APF as for half-mask air-purifying respirators, APF 10. An APF of 10 means that dust masks (if used properly) can be safely used in an atmosphere that has a hazardous concentration of up to 10 times the Permissible Exposure Limit (PEL) or other exposure limit for that hazard.

Dust Mask Limitations
Dust masks are designed to provide protection from a variety of contaminants. When deciding on the type of protection needed, always check with the manufacturer to ensure that the dust mask is the correct type of protection for the contaminant and level of exposure. When determining the exposure limit, be sure to check the Toxic and Hazardous Substances in 1910 Subpart Z and especially the Tables in 1910.1000, for your chemical exposure. Be sure to look at Table Z-3 for Mineral Dusts, including Inert or Nuisance Dusts, which may apply to your situation.

Another great resource is the NIOSH Pocket Guide2, which provides detailed information on a wide range of chemicals and will include the OSHA and NIOSH exposure limits, sampling methods, and recommended respirators. You can also look at the ACGIH TLV/BEI guidelines3. The Threshold Limit Values (TLVs), while not OSHA-enforceable, may be lower, more protective limits than the PELs. My recommendation is to always use the lower limits for employee protection.

As with any negative-pressure respirator that filters ambient air, some exposures won’t be protected by a dust mask, such as IDLH (Immediately Dangerous to Life and Health), including oxygen-deficient atmospheres. Be very sure that a disposable dust mask is correct for your situation and conditions. Note that there are filtering facepieces that are specifically designed for medical exposures. For example, a surgical N95 respirator is a NIOSH-approved respirator that has also been cleared by the FDA as a surgical mask. Always be sure that you have chosen the correct mask for the application and that you follow all of the manufacturer's recommendations and all OSHA requirements.

Additional resources for respirator users are available on the CDC/NIOSH website at


This article originally appeared in the November 2015 issue of Occupational Health & Safety.

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