Chapter IV. Escape Respirators
Escape devices have a single function: to allow a person working in
a normally safe environment sufficient time to escape from suddenly
occurring respiratory hazards. Given this function, selection does
not rely on assigned protection factors. Instead, these respirators
are selected based on a consideration of the time needed to escape,
and the likelihood of IDLH or oxygen deficiency conditions. Escape
devices can be separated into two categories: air-purifying respirators
and self-contained breathing apparatus. Air-purifying respirators
remove contaminants from the air by sorbent and/or filter media,
but because they do not provide air, these respirators cannot be
used in an oxygen-deficient atmosphere. Escape capabilities of air
purifying respirators can be summarized as follows:
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• Air-purifying respirators with particulate
filters or chemical cartridges are approved for escape from
atmospheres containing specific contaminants in concentrations
that are not immediately dangerous to life or health (IDLH)
and oxygen content of at least 19.5% by volume. This includes
half and full facepiece respirators that are routinely used
in many work environments. Mouthpiece-type cartridge respirators
(TC-23C) are approved for escape only.
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• Air-purifying respirators with canisters (TC-14G)
include the escape gas mask (canister) respirator, the gas mask
(canister) respirator, and the filter self-rescuer. |
The escape gas mask consists of a half-mask or a mouthpiece respirator.
The mouthpiece respirator can be used for short periods of time
to escape from low concentrations of organic vapor or acid gas.
The escape gas mask, which utilizes a half-mask, filters contaminants
from the air. These respirators may also be used to escape from
low concentrations of organic vapor or acid gas, but not from oxygen
deficient atmospheres. Escape gas mask respirators equipped with
full facepieces can also be used for escape from IDLH conditions
but not from oxygen-deficient atmospheres. These respirators may
be used for escape from contaminant concentrations above the IDLH
value provided that the maximum use concentration (MUC) for the
canister is not exceeded and adequate oxygen (=19.5%) is present.
Note that not all gas masks provide protection against carbon monoxide
(CO). Check the certification to determine if the respirator is
specifically certified for use against levels of CO that exceed
the exposure limit. Gas masks with full facepieces are also acceptable
for routine use in non-IDLH atmospheres. Gas masks with mouthpieces
are for escape only. No air-purifying device is suitable for escape
from a potentially oxygen-deficient atmosphere. The filter self-rescuer
unit is the mouthpiece device, which is designed to protect specifically
against atmospheres with not more than 1% carbon monoxide. The filter
self- rescuer is normally used in mining.
A new type of air-purifying escape hood that fits over the head
and seals at the neck has been developed specifically for escape
from chemical, biological, nuclear, or radiological exposures associated
with terrorism events. This type is not discussed further here as
terrorism-related selection is beyond the scope of this document.
See http://www.cdc.gov/niosh/npptl/guidancedocs/interesc0404.html
for additional information
A self-contained breathing apparatus (SCBA) provides air to the
user for escape from oxygen-deficient environments. Escape SCBA
devices are commonly used with full facepieces or hoods and, depending
on the supply of air, are usually rated as 3- to 60-minute units.
Self-contained self-rescuer (SCSR) devices have been approved by
MSHA/NIOSH for escape from mines, but these devices may also have
application in other similar environments. SCSRs are mouthpiece
respirators that provide a source of oxygen-enriched air for up
to 60 minutes. SCSRs are normally stored in mines and used for emergency
escape from mine disasters. All SCBA devices can be used in oxygen-deficient
atmospheres.
When selecting escape apparatus, careful consideration must be
given to potential eye irritation. This consideration is important
for determining whether a gas mask or SCBA equipped with a full
facepiece should be selected rather than a device equipped with
a half-mask or mouthpiece.
The majority of gas masks or escape gas masks can be used in situations
involving gases, vapors, or particulates. For escape from particulate-contaminated
environments, an air-purifying element must be selected that will
provide protection against the given type of particulate.
In addition to contaminants and concentration levels, the time
to escape the hazard must be considered. For example, escape SCBA
can have rated service lives of 3 to 60 minutes.
NIOSH intends to review the selection criteria for escape respirators
and will provide additional guidance in future revisions of the
RSL.
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