Operation; Environmental Factors - MSA ALTAIR 5X PID Operating Manual

4

Operation

Device operation is dialog driven from the display with the aid of the three function buttons
(→ chapter 3.2).
For more information, see the flow charts in chapter 11.
4.1

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 could shift.
Combined Humidity and Temperature Changes
When the device is calibrated in an dry, air conditioned environment and taken to a high temperature
and high humidity outdoor environment, a VOC Low or High alarm may be triggered by this sudden
change. It is recommended that the PID sensors be cleaned prior to this transition to avoid this situa-
tion, or to acclimate the sensor to the outdoor conditions in a known safe area.
ALTAIR 5X PID
Operation
US
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