Understanding Respiratory Protection Against SARS
SARS (severe acute respiratory syndrome) is a new respiratory illness that has been reported in Asia, North America, and Europe. SARS appears to spread primarily by close person-to-person contact with symptomatic individuals (e.g., persons with fever or respiratory symptoms). SARS can be spread by touching the skin of other people or objects contaminated with infectious droplets and then touching the eyes, nose, or mouth. Contamination occurs when someone with SARS coughs or sneezes droplets onto themselves, other people, or nearby surfaces. It also is possible that SARS can be spread further through the air by very small particles. This method is called airborne transmission, but investigations to date suggest that this type of transmission is unusual. It also is possible that SARS may be spread by other ways that are currently not known.
Most transmission of SARS to health care workers appears to have occurred after close contact with SARS infected individuals. CDC has therefore issued interim infection control recommendations for health care and other institutional settings (see Updated Interim Domestic Infection Control Guidance in the Health-Care and Community Settings for Patients with Suspected SARS, Interim Domestic Guidance on the Use of Respirators to Prevent Transmission of SARS, and Transport of Patients with Suspected SARS.)
These guides recommend that health care workers entering the room of a SARS patient and medical transport workers transporting a patient with suspected SARS use the following:
Infectious material deposited on personal protective equipment may cause it to become a vehicle for direct or indirect transmission. Therefore, care is needed when removing personal protective equipment to avoid contaminating skin, clothing, and mucous membranes. Standard procedures for removal of personal protective equipment that minimize the potential for self-contamination should be developed based on the equipment used, and healthcare and transport workers should be trained in these procedures. Hand hygiene should be performed following the removal of personal protective equipment.
A respirator is a personal protective device that is worn on the face, covers at least the nose and mouth, and is used to reduce the wearer’s risk of inhaling hazardous airborne particles (including dust particles and infectious agents), gases, or vapors. The many types of respirators available include (1) particulate respirators, which filter out airborne particles; (2) “gas masks,” which filter out chemicals and gases; (3) airline respirators, which use compressed air from a remote source; and (4) self-contained breathing apparatus, which include their own air supply. The category of particulate respirator can be further divided into (1) disposable or filtering facepiece respirators, where the entire respirator is discarded when it becomes unsuitable for further use due to excessive resistance, sorbent exhaustion, or physical damage; (2) reusable or elastomeric respirators, where the facepiece is cleaned and reused but the filter cartridges are discarded and replaced when they become unsuitable for further use; and (3) powered air purifying respirators (PAPRs), where a battery-powered blower moves the air flow through the filters.
An N-95 respirator is one of nine types of disposable particulate respirators.
Respirators that filter out at least 95% of airborne particles during “worse case” testing using a “most-penetrating” sized particle are given a 95 rating. Those that filter out at least 99% receive a “99” rating. And those that filter at least 99.97% (essentially 100%) receive a “100” rating.
Respirators in this family are rated as N, R, or P for protection against oils. This rating is important in industry because some industrial oils can degrade the filter performance so it doesn’t filter properly.* Respirators are rated “N,” if they are not resistant to oil, “R” if somewhat resistant to oil, and “P” if strongly resistant (oil proof). Thus, there are nine types of disposable particulate respirators:
NIOSH uses very high standards to test and approve respirators for occupational uses. NIOSH-approved disposable respirators are marked with the manufacturer’s name, the part number (P/N), the protection provided by the filter (e.g., N-95), and “NIOSH.” This information is printed on the facepiece, exhalation valve cover, or head straps. A listing of all NIOSH-approved disposable respirators is available at http://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/. If a disposable respirator does not have these markings and does not appear on one of these lists, it has not been certified by NIOSH. NIOSH also maintains a database of all NIOSH- approved respirators regardless of respirator type (the Certified Equipment List) that can be accessed at [http://www.cdc.gov/niosh/npptl/topics/respirators/cel/]).
More detailed respirator information has been published by NIOSH, CDC, at http://www.cdc.gov/niosh/npptl/topics/respirators/ and by the Occupational Safety and Health Administration (OSHA) at http://www.osha.gov/SLTC/etools/respiratory/index.html.
*The SARS virus has a “shell” composed of lipids, which are fats and oils. However, the amount of fat and oil in these tiny virus particles is extremely low and is not enough to affect the filter in the N-series respirator. Thus the N-series respirators such as N-95 will protect against SARS exposure.
Yes, workers can wear any of the types of particulate respirators for protection against SARS—if they are NIOSH-approved and if they have been properly fit-tested and maintained. All of the NIOSH-approved particulate respirators protect workers against SARS as effectively as the N-95 respirators.
A respirator will work only if it is used correctly. Thus the
key elements for respiratory protection are fit-testing and training of
each worker in the use, maintenance, and care of the respirator.
NIOSH considers each of the nine types of disposable particulate
In health care settings, the use of respirators by workers is regulated under the Occupational Safety and Health Administration (OSHA) standard for respiratory protection. The OSHA standard sets requirements for the fit-testing of respirators to ensure a proper seal between the respirator’s sealing surface and the wearer’s face. The OSHA standard also contains requirements for determining that workers can use respirators safely, for training and educating employees in the proper use of respirators, and for maintaining respirators properly. NOTE: Fit-testing and the other OSHA-required procedures are absolutely essential to assure that the respirator will provide the wearer with required protection. Detailed information on respiratory programs, including fit test procedures can be found at http://www.osha.gov/SLTC/etools/respiratory/index.html.
The CDC Guidelines for Isolation Precautions in Hospitals [http://www.cdc.gov/ncidod/hip/isolat/isolat.htm] recommends that health care workers protect themselves from any disease spread through the air (airborne transmission) by wearing a respirator at least as protective as a fit-tested N-95 respirator.† These guidelines were written before SARS was discovered, but they have been used to protect against other airborne diseases such as tuberculosis.
†Although N-95 respirators are sold outside the United States, other particulate respirators are also available. If you live in another country, your country may have its own standards for particulate respirators. The particulate respirators may have different names than those certified by NIOSH in the United States. If these respirators pass testing programs comparable to those used for N-95 respirators, they should protect against SARS as well as the N-95 respirators.
Usually, yes. An exhalation valve reduces excessive dampness and warmth in the mask from exhaled breath.
The valve opens to release exhaled breath and closes during inhalation so that inhaled air comes through the filter. Health care workers may wear respirators with exhalation valves unless the patient has a medical condition (such as an open wound) for which a health care worker would normally wear a surgical mask to protect the patient. Similarly, respirators with exhalation valves should not be placed on a patient to contain droplets and prevent spread of infectious particles; surgical masks are adequate for this purpose.
Once worn in the presence of a SARS patient, the respirator should be considered potentially contaminated with infectious material, and touching the outside of the device should be avoided. Upon leaving the patient’s room, the disposable respirator should be removed and discarded, followed by hand hygiene.
If a sufficient supply of respirators is not available, healthcare facilities may consider reuse as long as the device has not been obviously soiled or damaged (e.g., creased or torn). Data on reuse of respirators for SARS are not available. Reuse may increase the potential for contamination; however, this risk must be balanced against the need to fully provide respiratory protection for healthcare personnel.
If N-95 disposable respirators are reused for contact with SARS patients, implement a procedure for safer reuse to prevent contamination through contact with infectious droplets on the outside of the respirator.
Consider wearing a loose-fitting barrier that does not interfere with fit or seal (e.g., surgical mask, face shield) over the respirator.
Surgical masks are not designed for use as particulate respirators and do not provide as much protection as an N-95 respirator. Most surgical masks do not effectively filter small particles from air and do not prevent leakage around the edge of the mask when the user inhales.
If surgical masks do not protect against airborne diseases, why are surgical masks suggested for use against SARS when no N-95 respirators are available?
Surgical masks are recommended only as a last resort for health care and medical transport workers exposed to SARS patients when no NIOSH-approved respirator equivalent to or greater than the N-95 is available. SARS appears to be transmitted mainly through direct contact with infectious materials (including large respiratory particles), and surgical masks will provide barrier protection against droplets that are considered to be the primary route of SARS transmission. However, surgical masks may not adequately protect against aerosol or airborne particles, primarily because they do not effectively filter small particles from the air, they allow leakage around the mask, and they cannot be fit tested. Because scientists cannot currently rule out the spread of SARS through the air, CDC recommends a NIOSH-approved respirator equivalent to or greater than the N-95.
Surgical masks may also be placed on patients with communicable conditions like SARS to contain respiratory droplets and prevent spread of infectious particles.
Both CDC and the World Health Organization (WHO) recommend respirator use for the following workers only:
Respirators are not routinely needed (by staff or visitors) in other parts of hospitals or other health care facilities where there is no direct contact with patients.
Outside the health care and medical transport settings, CDC does not recommend the routine use of respirators. Most people who develop SARS become infected through contact with other people who are ill with SARS?not by breathing contaminated air. If a person does contact the SARS virus, it is most likely to be on a surface such as a door knob. The best protection from SARS in public places, (including workplaces other than health care and medical transport settings) is to wash your hands frequently and avoid touching your eyes or nose.
For more information about SARS
For the most current information about SARS as well as specific recommendations for health care workers, visit the following:
NIOSH SARS Web site: http://www.cdc.gov/niosh/topics/SARS/
CDC SARS Web site: http://www.cdc.gov/ncidod/sars/
WHO SARS Web site: http://www.who.int/en/