MSA ALTAIR 4XR, Operating Manual

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ALTAIR
®
4XR
21
Operation
US
3 Operation
Device operation is dialog driven from the display with the aid of the three Function buttons (see Fig.
1 "Device overview").
3.1 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.
Pressure Changes
If pressure changes rapidly (e.g., stepping through airlock), the oxygen sensor reading may temporarily
shift and possibly cause the device 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.
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.
Temperature Changes
The sensors have built-in temperature compensation. However, if temperature shifts dramatically, the
sensor reading may shift. Zero the device at the work site temperature for the least effect.