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Index
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CE
- Ceiling Limit
The
concentration which should not be exceeded at any time.
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IDLH
- Immediately Dangerous to Life or Health
The
IDLH value is based on the ability of a worker to escape
without loss of life, irreversible health effects, or other
health effects such as disorientation or coordination that
could prevent escape. It is the maximum concentration
allowed before which a highly reliable breathing apparatus
providing maximum protection for workers in required.
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LEL
- (Lower Explosive Limit) Example (Methane gas)
Methane
gas has a LEL of 5.53% by volume. If the atmosphere has
less that 5.53% methane,
an explosion cannot occur even if a source of ignition is
present. When the methane concentration reaches 5% an explosion
can occur if there is an ignition source. Each combustible
gas has it's own LEL concentration.
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Linearity
Quantitatively,
refers to the output signal in relation to the gas concentration.
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NEMA
Type 1
For
general-purpose indoor use. Provides protection against
incidental contact with the enclosed equipment.
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NEMA
Type 4
For
indoor or outdoor use. Provides protection against windblown
dust, rain, sleet and ice. Provides rust resistance. Provides
protection against direct water hosedown.
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NEMA
Type 4X
For
indoor or outdoor use. Provides protection against windblown
dust, rain, sleet and ice. Provides rust resistance. Provides
protection against direct water hosedown. Provides corrosion
resistance for indoor use.
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NEMA
Type 12
For
indoor use. Provides protection against dust, falling dirt
and dripping non-corrosive liquids.
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PEL
- Permissible Exposure Limit - OSHA
TWA
permissible concentrations, to which workers may be exposed
continuously, day after day, without adverse effects, for
a normal eight-hour workday and a forty-hour work week.
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REL
- Recommended Exposure Limit - NIOSH
The
TWA concentration permissible for up
to ten-hour workdays during a 40 hour work week.
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Repeatability
Relates
to the ability of sensors to repeat the measurements of
gas concentrations when the sensors are subjected to precisely
calibrated gas samples.
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Response
Time
The
time required for a sensor to read a certain percentage
of full-scale reading after being exposed to a full-scale
concentration of a given gas. Example: T80 = 30 seconds
means that a sensor takes 30 seconds to reach 80% of the
full scale reading after being exposed to a full-scale gas
concentration.
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Safety
Group (refrigerants)
This
is determined by a combination of flammability and toxicity.
"A1" rating denotes the safest refrigerants to
handle and "B3" denotes the most dangerous. Combustible
alarm systems are set to alarm at a low percentage of the
LEL of the target gas.
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STEL-
Short Term Exposure Limit
A
fifteen-minute TWA exposure which should
not be exceeded at any time during a work day even if the
eight-hour TWA is within limits. Exposures
at the STEL should not be longer than fifteen minutes and
should not be repeated more than four times per day. There
should be at least 60 minutes between successive exposures
at the STEL.
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TLV
- Threshold Limit Values - ACGIH
TWA permissible concentrations, to which workers may
be exposed continuously, day after day, without adverse
effects, for a normal eight-hour workday and a forty-hour
work week.
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TWA
- Time Weighted Average
The
average concentration of contaminants over a specified time
period.
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