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Home / Gas Detection - Fixed & Portable
Fixed gas detection in confined spaces

Invisible gas,
we see it at all times.

Distalarm, our fixed gas detection solution: detectors installed close to potential hazards monitor flammable, toxic and polluting gases on your premises 24 h/24. As soon as a threshold is exceeded, the control panel automatically puts your installation into a safe state — without waiting for anyone. And when the risk moves, flairgaz, our mobile detection solution, goes with your technicians.

View use cases Talk to an expert
51 yearsof expertise in gas detection
24 h/24real-time monitoring, without sampling cycles
ATEXcompliant for use in explosive atmospheres
Our two solutions

Distalarm monitors continuously. flairgaz works wherever you go.

Two complementary solutions: Distalarm, our fixed gas detection solution, monitors hazards at source 24 h/24 ; flairgaz, our mobile detection solution, supports your technicians during every spot check.

Fixed detection

Distalarm

Fixed gas detection control panel + continuously operating detectors

  • Standard electronic control panel, easy to install in your electrical cabinet
  • 4 interchangeable circuits, 4 relays as standard, up to 8 detectors across two channels
  • Simultaneous multi-gas detection on a single platform
  • Automatic controls: solenoid valve shut-off, alerts, safety shutdown — can be disabled in maintenance mode
  • Communication interface for your Building Management System (BMS)
  • Compatible with your existing detectors: upgrade without replacing them
  • CE certified, compliant with the ATEX Directive
Mobile detection

flairgaz

Portable dual-gas detector, simple and accurate

  • Flammable gas leak checks: methane, LPG, hydrogen
  • Carbon monoxide (CO) checks, which can be performed independently of leak detection
  • Time-stamped measurements
  • The essential tool for checking seals, flanges and fittings
  • Keeps technicians safe during on-site work
Gases monitored

A detector for every gas, a threshold for every detector

Flammable, toxic or polluting: our detectors are calibrated to the limits specific to each gas and your applicable regulations.

01

Flammable gases

Thresholds expressed as % of the LEL
CH₄

Methane — natural gas, boiler rooms

LPG

Butane C₄H₁₀ · Propane C₃H₈ — storage, tanks

H₂

Hydrogen — battery charging rooms, laboratories

02

Toxic gases

Thresholds expressed in ppm
CO

Carbon monoxide — incomplete combustion, car parks

NO₂

Nitrogen dioxide — exhaust emissions

H₂S

Hydrogen sulphide — sewer networks, treatment plants

03

Refrigerants

Refrigeration and air conditioning systems
HFO hydrofluoroolefins
R1234yfR1234ze
HFC hydrofluorocarbons
R134aR32R407CR410A
HFO / HFC blends
R448AR449AR454BR515B
HC natural refrigerant
R290 (Propane)
04

Solvents

Solvents and harmful vapours
XZ9600

Solvent — solvent vapour detection

How it works · Distalarm

From sensor to safety response, in real time

The detector measures

Positioned close to the hazard, the fixed detector measures continuously — with no polling cycle, in real time.

Thresholds trigger action

Pre-alarm, alarm, action levels: each threshold reached activates the corresponding relay on the control panel.

The installation enters a safe state

Gas solenoid valve shut-off, alarm transmission, ventilation control: the response procedure starts and your BMS is notified.

How it works · flairgaz

Locate gas leaks while keeping the operator safe

Switching on

A single press switches on the flairgaz. The gas sensor warms up and stabilises; zero calibration can be performed in clean air if required.

Gas leak detection

Along pipes, joints and fittings, the bar graph and progressive beeps track methane (CH₄) or hydrogen (H₂) concentrations in real time to pinpoint the leak. The orange indicator signals threshold 1; the red indicator and audible alarm signal threshold 2. Maximum mode retains the peak reading.

Operator protection

During leak detection, the flairgaz also monitors carbon monoxide (CO) around the technician: three alarm thresholds warn of a hazardous atmosphere. Readings can be stored with a date and time stamp.

Applications

Wherever gas can accumulate

Boiler room

Flammable gas detection, solenoid valve shut-off, power isolation: a complete safety response.

Parking

CO, NO₂, H₂S, H₂: ventilation precisely controlled according to measured pollution levels, rather than running blindly.

Industry

Furnaces, battery charging rooms, storage areas: leak detection and centralised monitoring for a rapid response.

Laboratory

Lab benches, Bunsen burners, fluid supply networks: room-by-room alarm identification and multi-hazard protection.

Greenhouse

Gas boilers and combustion-generated CO₂: monitor poor combustion and the deadly CO it produces, before people or plants are affected.

Refrigeration system

Refrigerant leaks: ambient monitoring detects environmental and financial risks, complementing localised detection.

Use cases, made simple

A leak waits for no one. Neither should your detection system.

Six real-world scenarios, six automatic safety responses.

Boiler room

Natural gas leaks, stopped at source

A smell of gas in the boiler room at night, with no one on site: every minute counts.

See the solution

Solution: as soon as the threshold is reached, the control panel closes the supply solenoid valve, transmits the alarm and can isolate the electrical power. Benefit: the installation is made safe before emergency services even arrive, in compliance with regulations.

Industry

Process leaks, centrally monitored

A leak somewhere in the process: without centralised monitoring, you are searching blindly.

See the solution

Solution: detectors report to the control panel and BMS in real time: the alarm source is identified for a fast, targeted response. Benefit: less production downtime, better-protected teams.

Industry

Battery charging rooms, under surveillance

Battery charging releases hydrogen: an invisible explosion risk that builds up over time.

See the solution

Solution: H₂ detectors monitor accumulation and control room ventilation before critical levels are reached, triggering an alarm if necessary. Benefit: a major risk continuously controlled, in compliance with the ATEX Directive.

Maintenance

Checking joints, flanges and fittings

Your technicians inspect hundreds of connection points, often in hazardous areas.

See the solution

Solution: flairgaz, our portable detection solution, pinpoints leaks (methane, LPG, hydrogen) while monitoring CO, with time-stamped readings. Benefit: fast, traceable inspections that also keep the technician safe.

Greenhouse

Greenhouses protected from carbon monoxide

Poor boiler combustion can fill a greenhouse with CO — lethal to people long before it harms plants.

See the solution

Solution: a CO detection system monitors the installation; if CO is accidentally produced, an alarm is raised at a very early stage. Benefit: staff and crops are protected, preserving greenhouse profitability.

Laboratory

Alarm sources identified, room by room

Multiple laboratories, active lab benches, accumulating hazards: where is the alarm coming from?

See the solution

Solution: the multi-zone control panel precisely identifies the alarm source and relays the information to the teams. Benefit: targeted evacuation and response, with no wasted time or uncertainty about the source.

What sets us apart

Gas detection, simplified

Experts for 51 years, Hesion designs, manufactures, calibrates and tests its systems in-house at its facilities in Yvelines, France. Simplifying detection is our promise.

French technology

From R&D to sensor calibration, everything is handled in-house or with local partners. Short supply chains, facilities in Yvelines.

Simple and reliable

Customer needs first, the environment second, technology third. Highly accurate, low-drift semiconductor sensors, ATEX compliant.

Plug & Work

No manufacturer commissioning required: your teams install, and we provide free telephone support. An approved partner network is available if needed.

Streamlined servicing

Maintenance through service exchange: calibrated detectors delivered ready to use, at lower cost, with a reduce-reuse-recycle approach.

Assess your gas risks

Whether you are an installer, engineering consultancy, distributor or inspection body, our project managers work with you to size the right system for your needs.

Contact us