Respiratory Protection Against Airborne Infectious Agents for Health Care Workers

Health care workers can be exposed to patients with infections. To minimize exposure to airborne infectious agents, health care facilities use isolation rooms, negative pressure ventilation, air filtration and disinfection. However, in certain settings administrative and engineering controls may not adequately protect health care workers from contaminated airborne droplets. Therefore health care workers should use respiratory protection.

Health care workers routinely use surgical masks as part of their personal protective equipment. However, surgical masks are not respirators and are not certified as such. They do not protect the wearer from inhaling small particles that can remain airborne for long periods of time. Surgical masks are effective barriers for retaining large droplets which can be released from the wearer through talking, coughing, or sneezing. Surgical masks are useful in many patient care areas. In fact, they may reduce wound site contamination during surgical or dental procedures. But surgical masks cannot be used as a protection from many hazardous airborne materials. The filter material of surgical masks does not retain or filter out submicron particles. In addition surgical masks are not designed to eliminate air leakage around the edges.

Respirators used in health care settings should be selected according to the efficiency of respirator filters in filtering aerosols and according to the type of procedure to be carried out.

As stated in the Canadian Biosafety Handbook Second Edition, "Where applicable, respiratory protection should conform to standard CSA Z94.4, Selection, Use and Care of Respirators" and "Using the wrong respirator or misusing one can be as dangerous as not wearing one at all." No single respirator (or any type of personal protective equipment (PPE)) can be expected to provide protection against all types of hazards. Be sure you are wearing the correct PPE for the task.

One of the most common respirators used in health care facilities is the type N95 disposable respirator. These used to be called dust/fume/mist (DFM) masks that were certified under a previous standard. N95 filters belong to a group of air purifying particulate filters. NIOSH (National Institute for Occupational Safety and Health in the U.S.) certifies these respirators (and other respirators) and these certified products are used in Canada.

The "N95" is one of three types of filters - N, R and P. These refer to the type of resistance they have to the degrading of their filtering efficiency when exposed to different kinds of airborne particulates, mists, etc. To help people remember which filters can be used for protection against different kinds of airborne particulates (e.g., dust, fume and mist). NIOSH provides the following guide:

N - Not resistant to oil

R - Somewhat Resistant to oil

P - Strongly resistant to oil (oil Proof)

The "95" in N95 refers to the filter efficiency. There are three levels of filter efficiencies - 95% (N95), 99% (N99), and 99.97% (N100 or HEPA filter) tested against aerosol (fine mist) droplets 0.3 microns in diameter. N95 type respirators are the respirators recommended by the Government of Canada and the U.S. Centers for Disease Control and Prevention (CDC) for use by health care workers in contact with patients with infections that are transmitted from inhaling airborne droplets (e.g., tuberculosis (TB); also recommended for health care staff working with patients having or suspected of having SARS, severe acute respiratory syndrome).

High risk procedures such as bronchoscopy and autopsy require additional protection. For example, protection may include full facepiece negative-pressure respirator, powered air-purifying respirators, and positive pressure airline respirators equipped with a half-mask or full facepiece. A supplied-air respirator with a hood may be needed for staff who cannot be properly fitted with respirators with a facepiece. In medical procedures that generate aerosol mists, goggles or face shields (with safety glasses or goggles) should also be used to prevent eye contamination.

Laser Plumes - Health Care Facilities has some additional, related information on controlling exposure to certain airborne contaminants in health care facilities.

If health care workers need to use a respirator then a respiratory protection program is necessary. The program should include the following procedures for:

• Selection and use of respirators.
• Respirator user training.
• Respirator face fitting.
• Inspecting, cleaning, maintaining and storing respirators.

In addition, CSA standard Z94.4 requires that the employer ensure the individual is medically approved to wear a respirator.

Other OSH Answers documents Designing an Effective PPE Program, Respirator Selection and Respirator Care have additional informational information that will assist in setting up a respiratory protection program.

As listed in the Canadian Biosafety Handbook:

• Complete respirator training and ensure proper fit through qualitative or quantitative fit-testing before beginning any activities that require a respirator.
• Perform a seal check every time the respirator is worn.
• Clean, and sanitize or decontaminate the respirator after every use according to the manufacture's instructions or safe operating procedures, even if it is stored in the containment zone.
• Prevent the filters or cartridge from becoming wet during decontamination. 
• Replace cartridges that are near the end of service life.
• Never reuse disposable respirators or masks. Decontaminate used respirators and masks before disposal.
• Inspect the respirator after use. Dispose, or repair any defective parts.
• Remove respiratory protection at the point at which a risk assessment deems it safe to do so upon exit from the containment zone.
• Reusable respirators should be stored so that they are protected from hazards that may affect the respirators (e.g., dust, sunlight, heat, extreme cold).