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pretation of how these data can be ap- exposure to fluids that may contain
plied to respiratory protection against M. bloodborne pathogens. In these settings,
tuberculosis; b) data on the efficiency of protection against both types of exposure
respirator filters in filtering biological should be used.
aerosols; c) data on face-seal leakage; and
d) data on the characteristics of respira- When operative procedures (or other proce-
tors that were used in conjunction with dures requiring a sterile field) are per-
administrative and engineering controls formed on patients who may have infec-
in outbreak settings where transmission to tious TB, respiratory protection worn by the
HCWs and patients was terminated. HCW should serve two functions: a) it
should protect the surgical field from the
1. The ability to filter particles 1 mm in size respiratory secretions of the HCW and b) it
in the unloaded state with a filter efficiency should protect the HCW from infectious
of > 95% (i.e., filter leakage < of 5%), given droplet nuclei that may be expelled by the
flow rates of up to 50 L per minute. patient or generated by the procedure. Res-
pirators with expiration valves and posi-
Available data suggest that infectious tive-pressure respirators do not protect the
droplet nuclei range in size from 1 mm to 5 sterile field; therefore, a respirator that does
mm; therefore, respirators used in health not have a valve and that meets the criteria
care settings should be able to efficiently in Supplement 4, Section I.A, should be
filter the smallest particles in this range. used.
Fifty liters per minute is a reasonable
estimate of the highest airflow rate an References reprinted from supplement
HCW is likely to achieve during breathing, 4 [CDC 1994, page 108 & page 112]
even while performing strenuous work
activities. 54. American National Standards
Institute. American national stan-
2. The ability to be qualitatively or quanti- dard practices for respiratory pro-
tatively fit tested in a reliable way to tection. New York: American
obtain a face-seal leakage of < 10% (54, National Standards Institute, 1992.
55).
55. NIOSH. Guide to industrial respi-
3. The ability to fit the different facial sizes ratory protection. Morgantown,
and characteristics of HCWs, which can WV: US Department of Health and
usually be met by making the respirators Human Services, Public Health Ser-
available in at least three sizes. vice, CDC, 1987; DHHS publica-
tion no. (NIOSH)87-116.
4. The ability to be checked for facepiece
fit, in accordance with OSHA standards 59. CDC/National Institutes of Health.
and good industrial hygiene practice, by Agent: Mycobacterium tuberculosis,
HCWs each time they put on their M. bovis. In: Biosafety in microbio-
respirators (54, 55). logical and biomedical laboratories.
Atlanta: US Department of Health
In some settings, HCWs may be at risk for and Human Services, Public Health
two types of exposure: a) inhalation of M. Service, 1993:95; DHHS publica-
tuberculosis and b) mucous membrane tion no. (CDC)93-8395.
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