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Breath of Fresh Air

Respiratory protection basics

Vince McLeod, CIH

Vince McLeod is an American Board of Industrial Hygiene-certified industrial hygienist and the senior industrial hygienist with Ascend Environmental + Health Hygiene LLC in Winter Garden, Florida. He has more...

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In the mid-1980s there was a fire in a feed and fertilizer store in Gainesville, Florida, where the Safety Guys lived and worked. Large quantities of smoke were generated, and police were called in to assist with cordoning off and securing the area. 

Many of the officers who were stationed downwind ended up with some significant symptoms of chemical exposure through inhalation of the smoke from these agricultural products. Some of our fire service personnel referred jokingly to these perimeter officers as the “blue canaries,” demonstrating the boundary where use of respiratory protection was needed. Shortly after this fire, we were asked to come help set up a respiratory protection program for the police department. To the best of our knowledge, the department didn’t have a single functional respirator available at the time of the fire.

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Things have come a long way since then, and use of respiratory protection in hazardous atmospheres is the norm. Yet there are still many misunderstandings and misconceptions surrounding the use of respiratory protection, whether it is in response to a possible chemical spill incident in the lab, processing chemical wastes in confined spaces, or just dealing with routine chemicals in your normal activities. So, as they say, let’s begin at the beginning.

Respirators are designed to prevent contaminated air from entering the body. There are several basic facepiece designs. Typically, one sees “half mask” respirators, which cover just the nose and mouth; “full face” respirators, which cover the entire face; and “hood” or “helmet” style respirators, which cover the entire head.

Respirators can protect the user in two basic ways. The first is by cleaning the “dirty” outside air that passes through a filter or adsorption bed or both when one inhales. This type is known as an air-purifying respirator (APR). The other main type of respirator protects the user by supplying clean breathing air from a remote source. The clean air can either be delivered via a supply line (supplied air respirators—SARs), or the clean air is packaged and carried with you in a tank (a self-contained breathing apparatus—SCBA), such as by a scuba diver.

When using APRs, one must first have a good idea of the nature and concentration of the contaminants against which one needs protection. For example, are you seeking protection against actual chemical hazards or simply avoiding exposure to unpleasant odors? In addition, one should ensure that there is adequate oxygen (at least 19.5 percent by volume) in the air, because the APR simply cleans the air and will not provide extra oxygen. If there is inadequate oxygen, as one might find in confined spaces, APRs cannot be used, and one must use a supplied air type.

For non-particulate contaminants, APRs should be used only for materials that have good sensory “warning properties” such as odor or irritation. This alerts the user to respirator failure either through seal leakage or cartridge overloading. OSHA requires use of cartridges/canisters with end-of-service-life indicators (ESLIs) or establishing cartridge change-out schedules to reduce the likelihood of contaminant breakthrough. These schedules will vary with the type of work done, the effort expended by the user, and the nature and concentration of contaminants encountered. The technical assistance group of your respirator manufacturer can help establish these change-out schedules. A certified industrial hygienist (CIH) can conduct exposure assessments to determine contaminant levels and establish change-out criteria through actual sampling of representative processes.

We must emphasize that respirators only reduce the amount of contaminants within the breathing air but don’t eliminate them altogether. Each type of respirator carries an “assigned protection factor,” which can be considered the theoretical amount of protection a properly fitted respirator might provide. The highest protection factor for APRs is only 50, according to NIOSH. APRs should be used only in relatively low-hazard areas where a single face respirator seal break might be unpleasant but not dangerous.

For high-hazard areas where atmospheres are oxygen deficient or otherwise immediately dangerous to life and health (IDLH), the use of supplied air or SCBA is required. Although one may still find some demandtype units where negative pressure with respect to the outside of the mask is created when taking a breath, these provide much less protection than the pressuredemand units. With pressure-demand supplied air, the space within the mask is maintained at a higher pressure than that of the outside air. Thus, if there is a break in the respirator seal, air should rush out of the mask, preventing the entry of any contaminants. The use of SCBA should be required for initial entry into clandestine drug labs due to the multitude and unknown concentrations of chemical hazards that may be present.1

A few words on OSHA regulations regarding respirator use.

The two basic requirements are that no one may use a respirator unless he or she is first given a medical evaluation and then tested to ensure that the respirator provided will actually fit to provide protection. In addition, anywhere respirators are used to protect one’s health against respiratory hazards, OSHA requires development of a respiratory protection program in accordance with 29 CFR 1910.134.2 Where respirators are used on a voluntary basis, fewer program elements are required to prevent hazards associated with respirator misuse. Suffice it to say that if your organization is using respirators, you should have a written program and an administrator well versed in this OSHA standard.

Before a user ever puts on a respirator, OSHA requires (and it makes good sense) assurance that users are physically capable of wearing a respirator. OSHA 29 CFR 1910.134 states “The employer shall provide a medical evaluation to determine the employee’s ability to use a respirator before the employee is fit-tested or required to use the respirator in the workplace.” It goes on to say, “Employees that use any respirators, including respirators such as air-supplied positive pressure face masks or hoods, must have a medical evaluation before use.”

One must also ensure that the respirator fits the wearer. A respirator that does not fit properly simply gives the false impression of protection and may be more dangerous than no respirator at all. There are specific fit-test protocols that are accepted by OSHA. The following is an excerpt from an OSHA compliance directive:

  1. Respirators must be fit-tested.
  2. A “test atmosphere” must be applied to assess the quality of fit.
  3. The fit-test must be applied to each and every employee required to wear a respirator.
  4. The fit-testing requirement applies to all negative-pressure respirators, including SINGLE-USE RESPIRATORS.

Respirators allow us to go where we could not normally enter safely. The use of respirators should not be taken lightly or in a cavalier manner. When used improperly, they can put people in greater jeopardy. Remember, respirators should be used only as a last line of defense when other control systems, such as adequate ventilation or hazard containment, are not feasible.


1. Guidelines for Law Enforcement for the Cleanup of Clandestine Drug Laboratories. US Department of Justice, Drug Enforcement Agency. Washington, D.C. 

2. Respiratory Protection, US Department of Labor, Occupational Safety, and Health Administration. Washington, D.C.