Explosimeters, flammable gas detectors, LEL measurement

Explosimeters are flammable gas detectors for leak detection of explosive gases such as natural gas, LPG (butane, propane), pentane, hydrogen, hydrocarbons, alcohols, solvents, ammonia, etc. They detect flammable gases and measure their quantity in the atmosphere according to the Lower Explosion Limit (LEL). There are two sensor technologies for explosive gas detection: catalytic sensors (the most commonly used) and infrared sensors for severe environmental conditions.

Our explosive gas detectors (fixed and portable)
  1. The MX4-EXPLO ATEX explosimeter is a portable flammable gas detector with a catalytic filament. Robust and lightweight thanks to its polycarbonate casing, it detects all explosive gases in the atmosphere according to the Lower Explosive Limit (LEL), such as natural gas, butane, propane, hydrogen, hydrocarbons, solvents or alcohols.

    • Detection of ATEX flammable gases from 0 to 100% LEL (Lower Explosive Limit)
    • Extremely rugged, shockproof, water and dust resistant (IP66 and IP67)
    • Audible 95 dB, visual and vibrating alarms for two thresholds, STEL and TWA
    • Optional clip-on pump for remote gas sampling
    • Safety approvals: ATEX, IECEx, CSA
  2. The Xam-EXPLO ATEX explosimeter is a portable explosive gas detector equipped with a catalytic filament sensor.  Robust and lightweight, it detects all explosive gases in the atmosphere, such as natural gas, butane, propane, hydrogen, hydrocarbons, solvents or alcohols, and indicates in real time the lower explosive limit in %LEL.

    • Detection of ATEX explosive gases from 0 to 100% LEL (Lower Explosive Limit)
    • Extremely robust, shockproof, dust- and water-resistant device (IP66 and IP67)
    • 95 dB audible, visual and vibrating alarms for 2 thresholds, STEL and TWA.
    • Optional clip-on pump for remote gas sampling
    • Safety approvals: ATEX, IECEx, CSA
  3. The Ventis MX4 portable 4-gas detector is very popular with confined space workers (see CATEC training). It detects explosive gases (0-100% LEL), lack of oxygen (O2), carbon monoxide (CO), and hydrogen sulfide (H2S). It can be used in diffusion mode or remote gas sampling mode with the optional VSP clip-on pump.

    • ATEX 4-gas detector: Explosive gases (0-100% LEL), O2, CO, H2S, NO2 or SO2 sensors too
    • 95 dB audible, visual and vibrating alarms for two thresholds, STEL and TWA (Threshold Limit Value and Average Exposure Value)
    • Very robust, shockproof, water and dust resistant (IP66 and IP67
    • Small and compact: first multi-gas detector of the size of a single gas
    • Optional VSP clip-on pump for remote gas sampling up to 30 m
  4. The X-am 2500 portable 4-gas detector (explosive gases 0-100% LEL, O2, CO & H2S) has been designed especially for industry, sanitation, public works, or interventions in confined spaces (CATEC). It is a versatile, high-performance device with an excellent quality/price ratio guaranteeing a high level of safety with low operating costs.

    • Portable ATEX 4-gas detector for explosive gases detection (0-100% LEL), O2, CO, and H2S, can also receive NO2 or SO2 sensors
    • Large LCD: easy navigation, comfortable reading of gas concentrations
    • Ergonomic design, robust, water and dust proof (IP67)
    • Long-life T4 NiMH battery (less than 4 hours charge time)
    • Optional clip-on pump for remote gas sampling up to 30 m
  5. Honeywell's fixed gas detector SensePoint is a cost-effective, high-performance gas transmitter for fixed gas detection installations. It is suitable for operation in potentially explosive atmospheres (ATEX zones) and detects explosive gases (hydrocarbons, solvents, alcohols), toxic gases (Cl2, CO, H2S, NH3, NO2, SO2) and lack of oxygen (N2, O2).

    • ATEX II 2 GD certified (gas and dust) and conforms to EC standards on electromagnetic compatibility
    • Honeywell Surecell high performance electrochemical cells
    • Four-way junction box for quick and easy installation
    • IP65 ingress protection against water and dust
    • Cost-effective and efficient solution with excellent value for money
  6. The SIL2 certified OLCT100 fixed gas detector is available in ATEX versions for explosive gas or intrinsically safe (IS) for toxic gases. With nearly 150 gases listed, this 4-20 mA linear output gas detector is suitable for explosive gases detections (hydrocarbons, solvents, alcohols), toxic, asphyxiating, and refrigerant leaks (freons, HFO, CFC, HFC).

    • Fixed gas detector for explosive gases, hydrocarbons, solvents, toxic gases, freons, VOCs, CO2
    • ATEX & SIL 2 certification for catalytic and infrared versions
    • Epoxy-painted aluminium housing (316L stainless steel optional)
    • Wheatstone bridge or linear 4-20 mA outputs
    • Power supply ranges from 15.5 to 32 VDC depending on the application
  7. The SensePoint XCD is an ATEX gas detector with a display and alarm relay for the detection of explosives (hydrocarbons, solvents, alcohols), toxic (CO, H2S, NO2), or asphyxiating (lack of oxygen or CO2) gases. A three-colour backlit LCD clearly and immediately indicates the status of the device (gas alarms, faults, etc.), even when it is far away.

    • ALL-IN-ONE fixed gas detector for monitoring explosive, toxic, or asphyxiating gases
    • LCD, alarm relay, fault relay, 4-20 mA, and RS485 Modbus outputs
    • 15.5 to 32 VDC power supply, 4-20 mA linear output, and relay output
    • Certifications ATEX Ex II 2 GD Ex d IIC T6 (gas and dust)
    • LM25 aluminium alloy or 316 stainless steel housing with epoxy paint
  8. The KwikSense is a digital gas transmitter ATEX dedicated to the detection of flammable gases, toxic gases, and volatile organic compounds. It has a digital display, 4-20mA and MODBUS outputs, and alarm relays for the detection of the gases Br2, C2H2, C2H3Cl, C2H6O, C3H8, C4H10O, C6H6, CH3OH, CH3SH, CH4, CH2O, Cl2, CO, CO2, COCl2, CS2, ETO, GPL, H2, H2O2, H2S, HCl, HC, HCN, HF, NH3, NO2, O2, O3, PCl3, PH3, POCl3, SO2 & COV.

    • Digital gas transmitter ATEX for the detection of explosive, toxic and asphyxiating gases, and VOC
    • Digital display and three-color LEDs to indicate detector status
    • Rugged, explosion-proof housing with cast aluminium alloy
    • 4-20mA, MODBUS, and 1 or 3 relay outputs depending on model
    • Excellent value for money with many accessories available
  9. Available for the detection of hydrocarbons and carbon dioxide (CO2), the GD10P infrared gas detector sets the standard for gas detection on offshore drilling platforms. The detector's optomechanical design is so stable that it provides an exceptionally high response time and an exceptional service life.

    • Fixed gas detector with infrared technology: hydrocarbon vapours and CO2
    • Fast response time and exceptional lifetime (> 15 years)
    • Continuous self-test function: signals optical defects or malfunctions to the control system
    • No saturation effect: the detector can measure gas concentrations up to 100 % vol
    • Factory calibration, no on-site recalibration
  10. The SearchPoint Optima Plus explosive gas detector has been specifically designed to detect hydrocarbons in certified potentially explosive atmospheres (ATEX). With a fast response time and a wide range of gases available, it is particularly suitable for offshore platforms, oil and gas terminals, refineries, etc.

    • IR technology with dual 4-beam source
    • Over 100 calibration curves available (hydrocarbons, solvents, alcohols)
    • Very short response time (T50 < 3 seconds - T90 < 4 seconds)
    • Worldwide ATEX, IECEx, UL, and CSA certifications and approvals
    • Very high reliability with an MTBF of over 28 years
  11. The OBSERVER-i is a third-generation ultrasonic gas leak detector for quick gas leak detection under pressure (from 2 bar). It is the first ultrasonic detector equipped with an artificial neural network (ANN) that uses patented technology to detect only gas leaks by suppressing unwanted background noise.

    • Quickly detects leaks of all gases under pressure (2bar)
    • Wide detection range while maintaining immunity to false alarms
    • Consistent detection coverage up to 28 metres away
    • Patented and proven Senssonic™ self-test function
    • A very cost-effective solution in the open air where conventional detectors are ineffective
  12. The Searchline® Excel detector is a linear gas detection barrier consisting of an infrared transmitter and a receiver that can be located up to 200 meters away. It is particularly suitable for methane, pentane, ethane, butane, propane, ethanol, ethylene, methanol, and propylene detection in petrochemicals and large-scale storage areas.

    • Highly accurate detection of hydrocarbons over distances of up to 200 meters
    • Fast response time with a T90 fewer than 3 seconds
    • Linear 4-20 mA and Modbus RS485 multidrop output
    • Simple installation and commissioning, one system replaces multiple point devices
    • Safety approvals: ATEX, IECEx, UL, CSA, FM, and GOST

Explosimeters or flammable gas detectors (fixed or portable) come in two large categories depending on the cell technology used.

Explosive gas detectors with catalytic cells 

Catalytic diffusion cells are the most widely used for the 4-gas detectors and combustible vapor detections. There is a correlation between the flammable gases presence and the temperature through the measurement principle. This temperature rise has been then transformed into a quantifiable quantity: the LEL (lower explosive limit). Although this measurement technology has an excellent price/performance ratio, it has some disadvantages:

  • It can only work with a minimum oxygen content of more than 10% (totally ineffective in an inert environment).
  • It does not discriminate the explosive gases present (same principle as the weighing scale: it gives the weight but does not say who is on the scale).
  • Premature wear in case of frequent or permanent detection of explosive gases (even when there are low LEL values).
  • High poison-sensitivity, such as silicone, lead, or sulfur compounds.

Flammable gas detectors with infrared cells 

Infrared absorption cells are used essentially for some explosive gas detection (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 subject to the permanent presence of flammable gas or cell saturation (measurement above 100% of the LEL).
  • Immunity against poisons like silicates or H2S.
  • Possible operation in inert atmospheres (without oxygen).
  • The measurement is almost infallible since the detector systematically goes into alarm as soon as there is a failure

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

ATEX Explosimeter

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

It is a portable version of personal protective equipment used in many sectors of activity, such as the oil and gas industries, heavy chemicals, metallurgy, water treatment, and sanitation. This PPE is also used to ensure safety during entry into 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 applied in a fixed version connected to a gas detection controller or a safety automaton. The flammable gas transmitter allows for securing entire installations subject to this type of risk.

LEL of the most common flammable gases 

Lower explosive limit expressed as a percentage of the total volume (%/vol.).

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: 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 page detection of volatile organic compounds.