Placement of Gas Detector Guidelines
Gas Detection systems only have industry approved best practice guidance notes for locating, placement and number of gas detectors. This is due to the complexity/speciality of gas detection due to the vast amount of gases being detected, over 400 gases with varied amount of properties and environmental influences factors, such as heat, that affect gases in different ways.
Flammable gas detectors are typically categorised into this group. Besides asphyxiation, flammable gases are generally not directly toxic and therefore, the strategic position of detectors is where the gas is expected to accumulate based on its relative density to air (heavier or lighter).
Typically gas detection systems in this section are used to monitor and either alarm or be part of processing control. This could be monitoring VOClevels pre and post filtering, Solvent Vapour (LEL) monitoring in drying ovens, Ventilation control in Car Parks and building etc. Location of these detectors will usually be based on the individual application, after considering the process, gases or vapours, air movement and temperatures involved. Applications falling into this category usually need a good dialogue between IGD and the plant designers to ensure the best placement of the detectors for them to be highly effective.
Life safety system
In such systems, the concern is that an asphyxiant or toxic gas is directly hazardous to personnel. The position of the gas detectors is based on the normal operating zone for people in the area of application. It is worth noting at this point that there maybe two sets of detectors involved with a life safety system. The first set of detectors perform as a process monitoring function, with the detection based on the relative density of the gas with respect to the air. This set of detectors is typically used to perform some type of function, for example: bringing on extra ventilation to clear a spill hazard.