Environmental Engineering Reference
In-Depth Information
concentration that is present is immediately dangerous to life or health
(IDLH). An IDLH atmosphere is defined as a very hazardous atmosphere
where exposure can cause serious injury or death in a short period of
time. Two kinds of supplied-air respirators are available. The air-line
type of supplied-air respirator delivers clean, compressed air from a sta-
tionary source delivered through a pressurized hose. The hose mask
type supplies clean, noncompressed air through a strong hose to a
respiratory inlet covering. Air may be supplied with a motor or a hand-
operated blower.
The supplied-air respirator has limitations. The biggest disadvan-
tage of supplied-air respirators is that losing the source of respirable
air supplied to the respirator inlet covering voids any protection to the
wearer. Moreover, mobility might be restricted by the inconvenience and
length of the air-supply hose (which cannot exceed 300 feet). Adequate
protection may not be provided in certain highly toxic environments.
The air intake of the device used must be fed uncontaminated air, which
might not be available.
When mobility is an issue and when respiratory protection against
all breathing hazards is required, the self-contained breathing appa-
ratus (SCBA) type of breathing device is required. Although the use of
SCBA allows more freedom and protection than the other types of res-
pirators, it must be kept in mind that it is important to monitor the
amount of air used and the amount still available for use in the worker's
air cylinder.
Selecting the correct type of respirator to wear is only one of sev-
eral considerations involved with respiratory protection. Because it
does little good (and could be disastrous) to have workers wear respira-
tors not suited for the hazard they are to be exposed to, OSHA requires
the employer to ensure that the proper respirator is selected for the
hazard involved. An employee, for example, who chooses to wear a half-
face-mask, air-purifying type of respirator in a confined space that has
an atmosphere composed of 100% carbon dioxide will become another
confined space fatality. Thus, employers must ensure that they provide
their workers with the correct type of respirator to protect them from
the respiratory hazards they are or might be exposed to.
Wearing the correct respirator is important, but making sure that
the respirator actually fits is just as important. OSHA requires that
workers who are designated to wear respirators in the workplace are
to be given respirator fit tests. The purpose of respirator fit-testing is
to provide the worker with a face seal on a respirator that provides the
most protective and comfortable fit. The two types of respirator fit tests
are quantitative and qualitative . In both tests, a harmless smoke, gas,
vapor, or aerosol is used to test for fit.
In a quantitative fit test, the person to be tested is instructed to
don his or her respirator and is then placed inside an enclosure for
exposure to a test agent (irritant smoke, banana oil, or saccharin). The
worker is carefully monitored and observed during a quantitative fit test
to determine if any of the test agent is entering the worker's mask. In a
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