9
Gas detectors usually fall into two groups for placement
Each site should be surveyed and assessed on its own merits. This document presents general
guidance only.
1. Plant Protection. Typically flammable gas detectors fall into this category. Aside from asphyxiation
flammable gases are typically not directly toxic and so detectors are placed strategically where the gas is
expected to accumulate based on its relative density to air (lighter or heavier)
Note that in many cases both life safety and plant protection sensors may be appropriate on a site. For
example a plant using liquid helium may have plant protection sensors at high level to ventilate roof
spaces in the event of leaks. However in the event of ventilation failure Helium could accumulate down
towards the zone where personnel operate. In this case a second set of life safety sensors would be
appropriate.
2. Life Safety Systems. Here the concern is that a toxic or asphyxiant gas is directly hazardous to
personnel and so the gas detection is placed based on the normal operating zone for the people present
Lighter than air gases, detectors placed at highest ceiling points
Consider fitting collector cones at lower level for gas bottle stores
boiler plant and gas meters (see separate application note).
400mm
1000mm
1800mm
Life Safety Zone
Consider ceiling divisions, follow rules for smoke detectors
Methane, Helium, Hydrogen, Ammonia etc
LPG, CO2
CO, CO2, O2
H2S, NO2, NO
HCN, HCL, HF
NH3 etc
Consider fitting splash/dust guards to protect low level sensors
Consider sensors in under floor areas/voids/drains where heavier than air gases are present
LPG
0-100%LEL
SN:20235-1-1 ADD:4110
GAS DETECTOR
LPG
0-100%LEL
SN:20235-1-1 ADD:4110
GAS DETECTOR
Siting Gas Detectors
Summary of Contents for 2-Wire Systems
Page 4: ...3 SECTION 1 MOUNTING DETAILS FOR EQUIPMENT...
Page 9: ...8 SECTION 2 SITING GAS DETECTORS...
Page 16: ...15 SECTION 3 GENERAL CABLING PRINCIPLES CABLE TYPES AND CABLE SIZING...
Page 23: ...22 SECTION 4 MAKING DEVICE CONNECTIONS TO DETECTOR NODES...
Page 35: ...34 SECTION 4 Control Panel Interfaces and Connections...
Page 51: ...50 Notes...
