Monitoring flammable gases

From a safety standpoint, priority must be given to the measures in item 1. Group 2 cannot be used as a sole protective measure for flammable gas or solvent vapors in industrial practice with sufficient reliability, but can be applied as the sole protective measure when only combustible dusts are present if the minimum ignition energy of the dusts is high (>10 mj) and the operating areas concerned can easily be monitored. 

Provide automatic sprinkler system/inerting gas Provide deflagration vents Provide deflagration suppression system Monitor flammable atmosphere/fire Provide nitrogen blocks (nitrogen injection to stop flame propagation) or other explosion isolation measures... 

Catalytic (Pellistor) Flammable gases Air Measures the heat output due to the catalytic oxidation of flammable gas molecules. A stream of the sample is passed over the sensor which is usually a ceramic bead impregnated with Pt or Pd. The temperature variations in the sensor due to reaction are monitored. Dependent on individual design. Flammable gas detector. Usually portable... 

Before designing enclosures for processes involving flammables, the consequences of poor ventilation that could concentrate the release above the lower flammable limit should be considered. Even if there are no ignition sources, continuously monitored combustible gas detectors should be placed in the enclosure. If all other sources of containment for flammables are inappropriate and enclosures are the only option, a means for extraordinary ventilation of even the smallest release should be provided. In addition, NFPA 68 (1994), Guide for Venting of Deflagrations, should be consulted... 

If flammable gas is detected and is above 10 percent but below 60 percent LEL, purge and ventilate the manhole for a minimum of 10 minutes, depending on the manhole or vault size. If combustible gas was detected but subsequently cleared, continue to monitor and ventilate to maintain the flammable gas level below 10 percent LEL. 

Using a calibrated gas monitor, the oxygen and flammable gas levels must be monitored from outside the space and it must be verified that the instrument is not damaged and calibration date is current. 

If the monitor for flammable gas indicates 10% of the LEL or greater, entry is prohibited. 

With flammable gases, eliminate all ignition sources (refer to Chapter 6). Possibly provide additional high/low level ventilation background gas detectors to alarm, e.g. at 40% of the LEL. With toxic gases, possibly provide additional local ventilation monitors connected to alarms appropriate air-fed respirators. (The flammable/toxic gas detectors may be linked to automatic shutdown instrumentation.)... 

Rarified Research operates a ram-fed incinerator for destruction of select wastes at its large, centralized research facility, including liquid flammable solvents in small plastic containers. The incinerator is fired by natural gas and is brick-lined. Temperatures are closely monitored, and stack emissions are routinely sampled. 

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