Prosense Safevader Series User Manual page 7

gas/air mixtures in particule per million (PPM) and Oxygen and CO2 in volume (VOL) units. The
enclosure protection is IP 65. For the determination of the measuring range and operating
conditions, the label on the detector should be consulted.
Not to be used in oxygen enriched atmospheres.
In conjunction with the central controllers Prosense detectors with preadjusted alarm
thresholds audible and visible alarm devices or automatic countermeasures can be activated
before the detected gases or vapours can form dangerous flammable or toxic mixtures with air.
SAFEVADER series with pellistor sensor for flammable gas detectors are designed to detect
gases or vapours in air and not inert or oxygen deficient atmospheres. Please be alerted in
following special conditions may have impact on measuring function due to the nature of
measuring method:
1. Very high gas concentrations
The measuring method of SAFEVADER series detector based on heat produced by reaction on
the oxidation of a flammable gas when pellistor sensor used. There is not enough oxygen in the
sensor to perform oxidation process correctly in case of high gas concentrations. Hence the
measuring signal decreases at high gas concentrations and even can lead to measuring signal
within the measuring range again. In case of high flammable gas concentration, do not reset
latching alarms without having ensured a safe condition in the environment via performing
necessary checks.
2. Minimum oxygen concentration
The measuring principle of heat of reaction needs a minimum oxygen concentration of 12 % by
volume for SAFEVADER series detector with pellistor sensor; otherwise the measuring values
will be too low because of oxygen deficiency.
3. Long-term gassing with methane at very low temperatures
If the Prosense SAFEVADER series flammable gas detectors with pelistör sensor are operated
applying with methane at very low temperatures, the measuring signal at long term exposition
may decrease after alarm activation and may lead to misinterpretation.
If a gas alarm occurs, necessary actions need to be taken immediately. The decrease of the
measuring signal should not mean that the gas concentration has been decreased. We
recommend to keep alarms on the associated controllers and not to reset these alarms without
performing measurement with an independent gas detector to make sure conditions are safe.
4. Avoid exposure to Silicon complex
Prosense pellistor sensors high level of resistance to catalytic poisons like Hydrogen Sulphide
(H2S) and Silicones such as HMDS (HexaMethylDoSiloxane). But it is not suitable to use in
environments which continous exposure of poisoning elements.
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