Gas Detector Alarm Set Point (Examples)

[1]		Setting	Unit	Remark
IR Point detector
flammable gas (HC) point detectors	Alert threshold	20%	LEL
	Alarm threshold	50%	LEL
flammable gas (HC) point detectors  in machinery enclosures or building containing a continuous or primary grade of release	Alert threshold	15%	LEL
	Alarm threshold	25%	LEL
flammable gas (H2) point detectors	Alarm threshold	5%	LEL
	Control action threshold	10%	LEL
Open path detector (최대 remote distance가 있음)	Low level alarm	0.5	%LEL*m	It gives an alarm if there is a flammable gas cloud of 5% LEL over a distance of 10m.
	High level alarm	1	%LEL*m

 

 

[2]
Type	Alarm Level 1	Alarm Level 2	Note
Flammable gas point sensor inside turbine / compressor hood / compartment	10% LFL	40% LFL
Flammable gas point sensor process plant and HVAC inlets	10% LFL	40% LFL
Flammable gas line of sight sensor	1 LFL-m	2 LFL-m	See Note (1)
Hydrogen sulphide (H2S) point sensor	10 ppm (vol)	40 ppm (vol)
Hydrogen sulphide (H2S) line of sight sensor	To be determined	100 ppm-m	See Note (2)
Hydrogen fluoride (HF) point sensor	5 ppm	10 ppm	See Note (3)
Carbon Dioxide (CO2)	5,000 ppm (vol)	30,000 ppm (vol)
Carbon Monoxide (CO)	25 ppm (vol)	200 ppm (vol)
Chlorine (Cl2)	1 ppm (vol)	3 ppm (vol)
Oxygen Deficiency	19.5 % (vol)
Oxygen Enrichment	23 %  (vol)
Sulphur dioxide (SO2)	2 ppm (vol)	5 ppm (vol)
Heat Detectors (fusible plugs, frangible bulbs, polyflow)	68 °C (155 °F)		See Note (4)
Notes
1. For comfined areas with "heavy HC" greater than C3, use 0.5LFL*m for alarm level 1.
2. H2S LOS are emerging into the market. Guidance for their use is currently under review.
3. These are typical values. Actual HF alarm levels are subject to local conditions and requirement.
4. In areas of high ambient temperature, heat detectors to be set at 30C(50F) above the anticipated ambient temperature or nearest standard fixed setting above 30C(50F).