MSA ALTAIR 5X Manual De Uso página 20

4 Operation
• Backlight turns on
• Alarm sounds (if active)
• Alarm LEDs flash (if active)
The 100 % Vol IR sensors have no alarm setpoints.
3.10 Gas Exposure of 100 % LEL
When gas reading exceeds 100 % of the lower explosive limit (LEL), the device enters a Lock Alarm state and displays
"XXX" in place of the actual reading.
WARNING!
A catalytic combustible gas reading of "XXX" indicates the atmosphere could be above 100 % LEL or 5.00 % Vol CH
an explosion hazard exists. Move away from contaminated area immediately.
Failure to follow this warning can result in serious personal injury or death.
For ALTAIR 5X IR devices with an enabled 100 % Vol methane IR sensor, the LockAlarm will clear, and the catalytic
combustible again displays combustible concentrations when the gas sample drops to a lower level. For devices without an
enabled 100 % Vol methane IR sensor, the user can clear the LockAlarm state only by turning the device OFF, and then
ON again in a fresh air environment. When catalytic combustible gas reading digits appear, the device is available for
measuring gases once again.
LockAlarm of the catalytic combustible sensor occurs during Bump Testing and calibration of a % Vol
combustible IR sensor.
After the IR sensor Bump Test, the LockAlarm must be cleared (as described above) before the catalytic
combustible sensor is again able to measure and provide readings.
NOTE: Check your national standard values for 100 % LEL.
4 Operation
Device operation is dialog driven from the display with the aid of the three function buttons (→
Interfaces).
For more information, see the flow charts in
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.
20
9 Appendix – Flow Charts
ALTAIR 5X / ALTAIR 5X IR
and
4
3.2 Device Hardware
US