Maintenance and Calibration Gasman
24
Gasman IR CO2 Personal Detector
The concentration of CO
2
in fresh air is 0.04% by volume. A correctly
zeroed Gasman IR CO
2
monitor will read 0.04% in uncontaminated
ambient air.
Before zeroing the Gasman must be in fresh uncontaminated air well away
from a building or any CO
2
emissions. Hold the unit well away from the
breathing zone of the operator – i.e. at arm’s length. When Gasman IR CO
2
is zeroed in fresh air it automatically sets the CO
2
baseline level to 0.04%.
Gasman IR CO
2
can also be set to zero in nitrogen using the PC interface
and Portables PC software. This is in effect a zero point calibration
rather than a normal zero. To do this, after uploading the instrument
configuration file, note the existing calibration gas level, then set the
calibration value to 0.00%, apply nitrogen gas and click the Calibrate
button. After this zero point calibration is completed, remember to re-set
the calibration gas level to its previous level.
Nitrogen for zeroing should be provided from a suitable gas bottle at a
regulated flow of 0.5 l/min (1 SCFH), connected to the standard flow cap
clipped over the sensor aperture. Recommended calibration gas is 2%
CO
2
in a background of nitrogen.
Care should be taken to vent the nitrogen flow away from the operator
and not allow nitrogen flow for longer than necessary to complete the
zeroing. If indoors it is recommended to vent gas out of a window or into
an extracted fume cupboard.
Ozone sensor
Due to the reactive nature of ozone (O
3
) special procedures should be
followed when calibrating gas detectors that incorporate an ozone sensor.
By following the guidelines for calibration below users will maximise the
protection level that their gas detectors give them.
Always calibrate Crowcon ozone detectors with ozone only.
Fittings
For ozone calibrations all fittings and pipework should be stainless steel,
brass, aluminium or PTFE. Fittings or pipework in other plastic materials
such as Tygon must not be used.
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