43
Operation
ALTAIR io360
US
6.4
Monitoring Combustible Gases
The detector has been optimized for a response to Methane. The detector can monitor these concentrations
in ambient air:
The detector displays the combustible gas concentration in % LEL or % Vol CH
4
on the Measuring screen
until another screen is selected or the detector is turned off.
WARNING!
A combustible gas reading of "100" or "5" indicates the atmosphere is above 100 % LEL or 5.00 % Vol CH
4
respectively, and an explosion hazard exists. Move away from contaminated area immediately.
Failure to follow this warning can result in serious personal injury or death.
6.5
Environmental Factors
A number of environmental factors may affect the gas sensor readings, including changes in pressure,
humidity and temperature. Pressure and humidity changes affect the amount of oxygen actually present in
the atmosphere.
6.5.1 Pressure Changes
If pressure changes rapidly (e.g., stepping through airlock), the oxygen sensor reading may temporarily shift
and possibly cause the detector to go into alarm. While the percentage of oxygen may remain at or near
20.8 % Vol, the total amount of oxygen present in the atmosphere available for respiration may become a
hazard if the overall pressure is reduced by a significant degree.
6.5.2 Humidity Changes
If humidity changes by any significant degree (e.g., going from a dry, air conditioned environment to outdoor,
moisture laden air), oxygen readings can be reduced by up to 0.5 %, due to water vapor in the air displacing
oxygen.
The oxygen sensor has a special filter to reduce the effects of humidity changes on oxygen readings. This
effect will not be noticed immediately, but slowly impacts oxygen readings over several hours.
6.5.3 Temperature Changes
The sensors have built-in temperature compensation. However, if temperature shifts dramatically, the
sensor reading may shift.
Gas Type
Response Factor
Methane
1
Propane
1.4
Hydrogen
1.1
Acetylene
1.2
Check your national standard values for 100 % LEL (EN60079-20-1).