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Zone 1: An area classified as Zone 1 is likely to have ignitable concentrations of flammable
gases, vapours or liquids present under normal operating conditions. Flameproof (Ex db)
detectors are suitable for use in Zone 1.
Zone 2: An area classified as Zone 2 is not likely to have ignitable concentrations of flammable
gases, vapours or liquids present under normal operating conditions. Flameproof (Ex db)
detectors are suitable for use in Zone 2.
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.
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 based on heat produced by reaction on the catalytic oxidation of a
flammable gas when pellistor sensor used. In case of high gas concentrations there is not
enough oxygen in the sensor to perform oxidation process correctly. Hence the measuring
signal decreases at high gas concentrations and even can lead to measuring signal within the
measuring range again. In this case do not reset latching alarms without having ensured a
safe condition by means of an independent gas concentrations measurement.
2. Minimum Oxygen Concentration
The measuring principle of heat of reaction needs a minimum oxygen concentration of 15 %
by volume; 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 PC3 series flammable gas detectors 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. In this conditions 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 making sure
conditions are safe.
PRS-UM-PC3-EN-Rev.04-06.2020
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