Catalytic diffusion cells are the most commonly used for 4-gas detectors and flammable vapor detection. Through the measuring principle, there is a relationship between the presence of flammable gases and temperature. This temperature increase was then converted into a measurable quantity: LEL (lower explosive limit). Although this measuring technology has an excellent price/performance ratio, it has some disadvantages:

• It can only operate with a minimum oxygen content of more than 10% (completely ineffective in an inert environment).
• It does not distinguish between explosive gases present (same principle as a scale: it gives the weight but does not tell who is on the scale).
• Premature wear if explosive gases are detected frequently or continuously (even with low LEL values).
• Those with high sensitivity to poisons such as silicon, lead or sulfur compounds.

Infrared absorption cells are mainly used for the detection of some explosive gases (when the IR curve is available). It is a more expensive technology than catalytic diffusion technology, but it has many real technical advantages:

• Very long life.
• They are not constantly exposed to flammable gas or cell saturation (measurement above 100% of LEL).
• Immunity to poisons such as silicates or H2S.
• Possibility to work in inert atmospheres (without oxygen).
• The measurement is virtually error-free because the detector systematically alarms if there is a malfunction

IR sensors, on the other hand, do not work with monochromatic cells such as hydrogen.

ATEX approval (for ATmosphère EXplosive ) indicates the capability of the equipment to integrate the high explosive risk zone by not supporting explosion triggering (flame, spark, etc.). Approved for use in an explosive atmosphere ATEX explocimeter (or ATEX detector for explosives) guarantees maximum safety for all teams working in a hazardous area.

It is a portable version of personal protective equipment used in many activity sectors such as oil and gas industries, heavy chemicals, metallurgy, water treatment and sanitation. This PPE is also used to ensure safety when entering confined spaces (as part of the CATEC system) and in public works. It is also an integral part of firefighter equipment.

In parallel, it is implemented in a fixed version connected to a gas detection controller or a safety automation . The flammable gas transmitter allows to ensure the safety of all facilities exposed to such risks.

The lower explosion limit is expressed as a percentage of the total volume (%/volume).

Acetone: 2.5% – Acetylene: 2.5% – Ammonia: 15.0% – Benzene: 1.2% – Butane: 1.9% – Ethanol: 3.3% – Hydrogen: 4.0% – Carbon monoxide: 12.5% ​​– Methane CH4: 5.0% – Methanol: 6.0% – Pentane: 1.4% – Propane: 2.1% – Styrene: 0.9% – Toluene: 1.1% – Xylene: 1.1%.

For benzene, styrene, toluene and xylene, see also the detection of volatile organic compounds page .