Aerosol transmission: Occurs by dissemination of either airborne droplet nuclei or small particles containing the infectious agent. This can include respirable particles (mass median aerodynamic diameter smaller than 5 µm), thoracic particles (mass median aerodynamic diameter smaller than 10 µm), and inspirable particles (mass median aerodynamic diameter smaller than 100 µm).
Air-purifying respirator: A respirator with an air-purifying filter, cartridge, or canister that removes specific atmospheric contaminants by passing air through the air-purifying element. Air-purifying respirators are either powered or nonpowered.
ASTM: American Society for Testing and Materials. A nonprofit organization that develops standard testing methods by the consensus of volunteers representing manufacturers, users, and others.
Avian influenza: A type of influenza A infection caused by avian (bird) flu virus, such as type H5N1. Spread of the virus from person to person has been rare thus far and has not extended beyond one person. Because these viruses do not ordinarily infect people, there is little or no immune protection against them in humans. This relatively unusual set of circumstances, combined with absence of a vaccine against H5N1, sets the stage for a possible influenza pandemic.
Cleaning: The removal of surface dirt.
Contact transmission: Spread of infection through (a) direct (body-to-body surface contact) or (b) indirect means (contact with contaminated intermediate objects, such as hands, or inanimate objects, such as countertops).
Cough etiquette: A form of respiratory hygiene that entails voluntary covering of coughs and sneezes with one’s hand, handkerchief, tissues, etc. Because they can be discarded and thus reduce risk of indirect transmission, disposable tissues are preferable to handkerchiefs.
Critical item: One that enters a sterile body cavity, thus requiring sterilization prior to use.
Decontamination: The removal of virulent human pathogens.
Degerming: Mechanical removal of most microbes.
Disinfection: The destruction and removal of pathogenic organisms, especially by means of chemical substances.
Disposable respirator: A respirator that is designed to be discarded after contamination, excessive resistance to breathing, or physical damage, or when odor breakthrough or other warning indicators render the device unsuitable for further use. (See Respirator)
Droplet transmission: Spread of infection through relatively large droplets (≥ 5 µm) propelled a short distance (usually less than 3 feet or 1 meter) by coughing, sneezing, or talking, which then come into contact with the oral or nasal mucosa or conjunctivae of a susceptible host.
Elastomeric: Pertaining to various polymers having the elastic properties of natural rubber. Used in some tight-fitting respirator facepieces.
FDA: Food and Drug Administration. Regulates all personal protective equipment used in a healthcare environment.
Filter: A component used in respirators to remove solid or liquid aerosols from the inspired air.
Filtering facepiece: A type of disposable particulate respirator in which the filter is an integral part of the facepiece or the entire facepiece is composed of the filtering medium. The N95 filtering facepiece is the least expensive and most commonly used. (See Respirator)
Fit check: An action conducted by the user each time the respirator is donned to determine if the device is properly seated on the face. Fit-checking, like the initial fit-testing, is an essential prerequisite for effective respirator use. (Synonym: User Seal Check)
Fit factor: Quantitative estimate of the fit of a particular respirator to a specific individual. Typically estimates the ratio of the concentration of a substance in the ambient air to its concentration inside the respirator when worn. (See Fit Test)
Fit test: Assessment of the status of the seal between the respirator and the wearer’s face. Fit-testing may be qualitative or quantitative. Qualitative fit-testing uses the wearer’s ability to taste or otherwise detect a test aerosol to ensure fit. Quantitative fit-testing requires more complex test equipment and provides an actual measure of the fit factor. Fit-testing is an essential prerequisite for effective respirator use and must meet OSHA respiratory protection standards.
Full facepiece: Tight-fitting respirator that covers the entire face from below the chin to the hairline.
Half mask: Tight-fitting respirator that covers the nose and mouth and fits under the chin.
Hand hygiene: Hand washing with either plain or antimicrobial soap and water and/or use of alcohol-based products (gels, rinses, foams) that do not require the use of water. In the absence of visible soiling of the hands, alcohol-based products are preferred over soap and water. Hand hygiene has frequently been cited as the single most important component of infection control.
Healthcare worker: Any individual working in a healthcare facility—e.g., nurse, physician, physiotherapist, transporter, phlebotomist, cleaner, laboratory worker, prehospital personnel, clerk—whether or not that person is employed by the facility.
HEPA filter: High Efficiency Particulate Air filter: A filter that is at least 99.97 percent efficient in removing monodisperse particles of 0.3 µm in diameter. A NIOSH-certified P100 particulate filter is equivalent.
Influenza A: A common type of influenza with 16 known surface hemagglutinin proteins and 9 known surface neuraminidase proteins. Each combination of surface proteins represents a different influenza A subtype. Avian influenza is the H5N1 subtype.
Inspirable particles: Particles having a mass median aerodynamic diameter smaller than 100 µm.
Loose-Fitting facepiece: A type of respiratory inlet covering designed to form a partial seal with the face and used with a PAPR or supplied-air system.
Low-level disinfection: Process that eliminates most bacteria and some viruses and fungi but may not kill resistant microorganisms.
Mask: Any material or device covering the nose and mouth.
Medical mask: An unfitted mask worn by an infected person, healthcare worker, or member of the public to reduce exposure to or transmission of body fluids that may spread infection. Medical masks may be used as barriers against disease transmission by fluids, especially blood, and some large droplets, but they are not designed to protect the wearer from entry of infectious particles via leakage around or through the mask. (See Procedure Mask and Surgical Mask.) The FDA classifies all medical masks as “surgical” masks, although these masks have many nonsurgical applications outside the operating room. The committee has chosen the generic term “medical mask” to apply to all unfitted (nonrespirator) masks used for medical purposes.
Medical mask/N95 filtering facepiece respirator: A NIOSH-approved N95 respirator that also meets the FDA’s fluid-resistance requirements.
N95 filtering facepiece respirator: A disposable respirator with a filtering facepiece that has been tested and certified by NIOSH and meets the NIOSH criteria for a minimum 95 percent filter efficiency, not to be used
in an environment with an oily atmosphere. In this report the term “N95 respirator” refers to a disposable N95 filtering facepiece.
Negative-pressure check: A maneuver to check the respirator’s seal to the user’s face, in which the user blocks the respirator inlet path (i.e., the inlet valve, canister, or cartridge), inhales gently so that the facepiece collapses slightly, and then holds his or her breath for 10 seconds. If the facepiece remains in its sealed condition and no inward leakage of air is detected, the fit of the respirator is considered satisfactory.
Negative-pressure respirator: A nonpowered air-purifying respirator in which the air pressure inside the facepiece is negative during inhalation with respect to the ambient air pressure outside the respirator.
NIOSH: National Institute for Occupational Safety and Health, a federal agency under the Centers for Disease Control and Prevention that trains occupational health and safety professionals, conducts research on health and safety concerns, and tests and certifies respirators for workplace use.
Noncritical item: One that contacts intact skin. Requires low-level disinfection.
NPPTL: National Personal Protective Technology Laboratory: A division of NIOSH that among other tasks performs respirator certification tests.
OSHA: Occupational Safety and Health Administration, U.S. Department of Labor. Responsible for establishing and enforcing safety and health standards in the workplace.
Pandemic: Worldwide outbreak of an infectious disease.
Particulate respirator: A NIOSH-approved air-purifying respirator meeting certain criteria in specific NIOSH/NPPTL tests. Particulate respirators remove only particles from the air. Other types of air-purifying respirators remove vapors, gases, or chemicals.
Personal protective equipment (PPE): Facemasks (including respirators and medical masks), gloves, gowns, goggles, or faceshields used to reduce transmissibility of infection or exposure to other hazards.
Positive-pressure check: A user seal check in which the user closes off the exhalation valve and exhales gently into the facepiece. The face fit is considered satisfactory if a slight positive pressure can be built up inside the facepiece without any evidence of outward leakage of air at the seal.
Powered air-purifying respirator (PAPR): Respirators that use a blower to draw air through filters.
Procedure mask: One of two kinds of medical mask (the other type is a surgical mask). Procedure masks are flat-pleated or duck-billed in shape and fasten to the head with ear loops.
Reaerosolization: The process by which any aerially deposited material can be resuspended.
Respirable particles: Particles having a mass median aerodynamic diameter smaller than 5 µm.
Respirator: A device approved by NIOSH that when properly fitted protects the wearer against inhalation of harmful atmospheric contamination. In the context of this report, unless otherwise specified, the term “respirator” refers to a NIOSH-approved filtering facepiece particulate respirator. Properly fitted respirators, such as the N95, provide better protection against airborne transmission of infectious particles than do medical masks. (See N95 Filtering Facepiece Respirator)
Respiratory hygiene: Containment of respiratory secretions containing infectious particles disseminated by, for example, coughing or sneezing. May be done voluntarily as part of cough etiquette or through placement of a surgical or procedure mask on the individual who is coughing.
Reuse: Repeated use of a respirator or medical mask. This can be use over an extended period of time, or use following cleaning and disinfection.
Sanitization: Removal of contaminants and inhibition of the action of infectious agents.
Semicritical item: One that contacts mucous membranes or nonintact skin. Requires high-level disinfection.
Single-use respirator: A respirator without a replaceable filter, intended to be discarded after excessive resistance to breathing, reduction in filtration capacity, hygienic considerations, or physical damage that renders it unsuitable for further use. A filtering facepiece is one type of single-use respirator.
Social distancing: Public health measures targeted at minimizing nonessential close contact with others, e.g., temporary closing of schools to reduce influenza transmission among children.
Sterilization: The complete elimination of all forms of microbial life.
Surgical mask: One of two kinds of medical masks. Surgical masks, which were originally designed to protect the operating field from contaminants generated by the wearer, are of two main types: (1) flat-pleated or duck-billed in shape, conforming to the bridge of the nose with a flexible piece and affixed to the head with two ties and (2) premolded, conforming to the bridge of the nose with a flexible piece and adhering to the head with a single elastic. In the context of this report, unless otherwise specified, a surgical mask has passed certain ASTM tests required by FDA.
Thoracic particles: Particles having a mass median aerodynamic diameter smaller than 10 µm.
Tight-fitting respirator: Type of respiratory inlet covering that requires a complete seal with the face of the wearer. Available as half masks and full facepieces.
User seal check: An action conducted by the user each time the respirator is donned to determine if the device is properly seated on the face. A user seal check, like the initial fit-testing, is an essential prerequisite for effective respirator use. (Synonym: Fit Check)