Agriculture Reference
In-Depth Information
Figure 6.16 Qualitative fit testing is performed every time a mask is repaired
or new mask is used (University of Wisconsin, 40-hour OSHA training,
1991).
The second method for testing the facepiece seal is to close the exhalation
valve with your palm and exhale gently into the facepiece. If slight pressure
builds up inside the facepiece without any evidence of outward leakage, the
respirator probably fits tightly enough and will work correctly. This method is
not appropriate for respirators with an exhalation valve cover that would have
to be removed first. Figure 6.17 illustrates a negative pressure fit check.
Loose -fitti ng r e spi r ator s are powered air-purifying respirators that
constantly pump air through a cartridge or canister into a loosefitting hel-
metlike or hoodlike head covering. The positive outward pressure caused by
the steady outflow of air prevents contaminants from entering the headpiece.
The purified air circulates over the user's head, face, and neck and provides
some cooling.
Not all loose-fitting respirators move the air at the same rate. Most pes-
ticide handling tasks require a minimum airflow rate of 4 cubic feet per min-
ute. If you are doing physically strenuous work, use a respirator with an air-
flow rate of at least 6 cubic feet per minute.
Loose-fitting respirators do not have to form a seal on your face, so peo-
ple with facial hair can use them safely. They do not require extra lung power
and are not nearly as tiring or as hot as face-sealing respirators.
 
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