MAN0597 ISSUE 08 - 02/04
2302M5030
4. OPERATION
55
Flammable sensors may be affected by exposure to Silicone
substances; organic phosphorus containing compounds and
halogenated organic compounds. Although the flammable
sensors used in Impact and Impact Pro have a high resistance
to Hydrogen Sulfide (H
2
S) poisoning some loss in sensitivity
should be expected. Therefore it is strongly recommended
repeated gassing with H
2
S or gas alarms on the H
2
S channel
should be followed by checking and if necessary re-calibration
of the Flammable sensor. The sensors on average will lose
approximately 20% of their sensitivity when subjected to forty
applications of H
2
S for a period of 1 minute each.
The toxic sensors are designed to be gas specific, minimising
the effects of common cross-interfering gases. The table
below summarises the effect of various gases on the Carbon
Monoxide and Hydrogen Sulfide sensors.
Applied Gas H
2
S Response
(ppm)
CO Response
(ppm)
Acetone (1000ppm) 0 0
Acetylene (40ppm) 0 80
Ammonia (50ppm) 0 0
Carbon Monoxide (50ppm) 0 50
Carbon Dioxide (5000ppm) 0 0
Chlorine (0.5ppm) 0 0
Ethanol (2000ppm) 0 3
Ethylene (100ppm) 0 85
Hydrogen (100ppm) 0 20
Hydrogen Sulfide (10ppm) 10 0
Iso-Propanol (200ppm) 0 0
Nitric Oxide (25ppm) 0 4
Nitrogen Dioxide (3ppm) 0 0.5
Sulfur Dioxide (2ppm) 0 0
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