Area Gas Alarms – Who needs Them?

Some Background on Area (Sentinel) Type Gas Alarms.

Area or sentinel gas alarms have been available in various forms for many years. Initially these consisted of an alarm box attached to another portable gas detector that triggered at a defined concentration. Then came bespoke units – linked by cables to form a grid.

In recent years, area alarms have become more complex with wireless grid systems now interacting with remote computers and isolation controls.

The basic requirements for these instruments are: durability, stability, extended run times and an alarm, that is extremely easy to perceive (both visual and acoustic).

Effectively you could say, “they’re a multi-gas detector with a large battery and flashing lights.” (My apologies to any manufacturers who disagree – but feel free to comment.)

Why Use Area Gas Detectors?

Area gas alarms can be useful in a number of applications, for example:

  • during entry into confined spaces
  • while breaking containment in the oil, gas and chemical industries
  • to replace a fixed gas alarm system during maintenance or shutdowns, etc..

Suppliers and manufacturers will often tell us – “by positioning such devices in suitable locations around the workplace, a virtual gas free fence line can be created, producing safe working zones and escape routes.”

So on first sight, area gas alarms appear to be a fantastic solution to many tricky situations where flammable, and toxic gases may collect. The same if true when low or raise oxygen is the hazard.


“A fully integrated web of highly sophisticated gas alarms would therefore appear to be just what is needed!”

However, there are many pros and cons to area gas detectors, and their value very much depends upon how you use and position them. To illustrate, imagine you are asked to detect a lighter than air flammable gas such as methane. The task also includes monitoring an area in which more than one worker is active.

  • Many people would simply take a suitable area detector and position it centrally in the workplace.
  • Others may suggest, positioning them downwind of any potential release points.
  • Some upwind of the work location.
  • Still others may suggest, purchasing lots on units and connecting them into a grid system around the perimeter and within the workplace!

A bit confusing?

How about work within confined spaces, where should area gas detectors be placed then?

  • Could these include, poorly ventilated areas where gases may be trapped or collect, such as: low points or locations not influenced by a through draft; compartments and chambers and baffled tanks. Or even all of the above?
  • And how about, next to potential gas release points, and/or the entrance?

Which is right?

“The truth is, without a qualified and experienced authorised gas tester undertaking a suitable task specific risk assessment, it is impossible to say!” 

Or do you need them at all? – Well @gt have recently designed a whole new module based on the use of area gas detectors.  By attending one of these classes, @gt’s go back to the workplace with the answer to the question. “And trust me, they often save a lot of money as a result.”

Question for Readers:

  1. Having placed your area gas detector in its intended position – how far away from this point will it be able to detect gas? (comments please below ;0)

The answer to this question may assist you in the correct use and positioning of area gas detectors.

For more on this subject we suggest contacting us or joining our members area.


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