Answer / ajith294

Fire and gas system usually as part of a saftey system. the
percentage of Lower Explotion limit shall be dectected by
GAS detector and gives the alarm ,normally 20% is High and
40% is High High alarm.

catalytic bead sensor, semiconductor sensor, infrared point
sensor and ultrasonic sensor are using to detect the gases.

there was no establised standared to difine zero air for
calibration. some procedure says pure nitrogen and some
uses sytetic air. But much more realisitc and practical
using ambient air for zero calibration , when area is
considered to be clean.

for span calibration using 2.5 %Methene (CH4) and balance
nitrogen mixer. 2.5 %Methene (CH4)is equal to the 50 % of
LEL.

Answer / mohamed yousuf

fire and gas system is nothing but to detect the toxic,
flamable and combustible gases in the plant and also for
giving the awarness of the hazardous through beacons and
loudspeakers.

different between calibration range and instrument range ?

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