5.3 Inspection and Maintenance
5.3.1 Calibration Intervals
Status Scientific Controls advise that calibrations should be performed at no longer than six
monthly intervals (this can be arranged with Status Scientific Controls as part of a maintenance
contract).
If a pellistor-based sensor is known to have been exposed to a poison (refer to section 5.5.1) it
must at least be recalibrated. However Status Scientific Controls strongly advise sensor
replacement in these circumstances.
5.3.2 Routine Inspection
The detector heads will provide accurate fault free service but they rely upon sensible
housekeeping and regular calibrations. It is advisable to periodically inspect the detector head
installation:
• Check cables to ensure no damage has occurred.
• Clean detector heads using a DAMP cloth.
• Inspect detector heads and ensure the sensor housing apertures are not obstructed.
The time interval between routine inspections will depend upon the area in which the head is
installed. A clean laboratory installation may only require inspection at the time of calibration;
whereas an installation in a particularly dirty environment may require weekly inspections. It is the
responsibility of the system engineer to assess the installation environment and determine the
frequency of routine inspections.
5.4 Calibration
In order to carry out calibration of the gas detector, refer to the relevant instruction manual for the
product concerned.
5.5 Gas Detector Contaminants
The information provided in section 5.5 and its associated sub-sections is taken from the sensor
manufacturers ‘Product Data Handbook’.
5.5.1 Flammable Gas Detectors
Flammable gases can be detected by using either infrared or pellistor type gas detectors.
Infrared gas detectors have the advantage of being immune to chemical ‘poisoning’ and providing
a long operational life. However, they will not detect Hydrogen.
Pellistor type gas detectors are relatively low cost but are prone to chemical ‘poisoning’ as
detailed below.
The following information relates only to flammable gas detectors containing pellistors.
Certain substances are known to have a detrimental effect on gas detectors containing pellistors.
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