How does a gas detector work?

There have been gas detectors for as long as people have been aware of the harmful effects of gases in confined spaces. In the early days of mining, well before the development of electronic sensors, canaries were used.
They were taken underground in cages and if they stopped singing or died, then the miners would be alerted.

We’ve come a long way since the 19th and early 20th centuries. Now gas detection methods are much more precise – and much less harmful to animals.

How a modern gas detector works

Gas detectors use a sensor to measure the concentration of particular gases in the atmosphere. The sensor serves as a reference point and scale, producing a measurable electric current when a chemical reaction caused by a specific gas occurs. The sensor will monitor these currents and alarm the user when the presence of gas approaches an amount that is hazardous.

Early instruments were made to detect just one gas but now they can measure several at once – most commonly, oxygen (O2), flammable gases or vapours (LEL), hydrogen sulphide (H2S) and carbon monoxide (CO). These are the gases that a 4-gas detector monitors, the minimum requirements set out by SOLAS Regulation XI/1-7.

The sensor

Most portable gas detectors use a pellistor/catalytic bead LEL sensor. To function accurately, it requires a minimum of 10% oxygen in the environment to avoid the build-up of tar and unburned fuel on the activated ring.

Theoretically, the sensor can last up to four years but it is very sensitive and can easily break if the monitor is knocked or dropped.

Most sensors will be reaching the end of their life by the time they are three years old and will need replacing. This can be a costly process that will leave the detector out of action, so you also need extra instruments to make sure you’re covered while the repair work is being carried out. Other components like backlight screens and audio alerts will begin to develop faults too so it’s important to keep detectors well-maintained.

Calibration

Pellistor sensors can be poisoned by many things, including the gases they’re detecting.

Contaminated sensors may not register dangerous gas levels and will become gradually slower and more unresponsive over time. Their performance depends on thorough testing using calibration and bump-testing to make sure they’re always measuring the correct amount of gas to keep seafarers and vessels safe.

Infrared sensors

These don’t require oxygen so will work in completely inert atmospheres. This makes them ideal for confined space detection and taking samples from tanks where a lack of oxygen is an issue. They’re also immune to sensor poisoning so there’s no need for calibration to ensure the gas detector is functioning correctly.

A traditional pellistor sensor uses a heated aluminium coil that drains a large amount of power. However, gas detectors that use infrared sensors are much more energy efficient with batteries that won’t require charging as frequently.

MGC Simple+

The cutting-edge infrared technology in the MGC Simple+ means its battery lasts for three years without charging – a world first for a portable gas detector.

It doesn’t require calibration (although it can be easily set-up to do this to meet the specifications of a risk assessments or safe systems of work) and is rated IP68 so is protected from even the finest dust and can be submerged in water for 30 minutes at a depth of 1.5m.

MGC Simple+ also comes with a full warranty for three years so you’ll never incur extra repair costs.

At the end of those three years, you simply replace the detector – a much cheaper option than spending money maintaining an old instrument. Buying a new detector means that you’ll also have a new three-year warranty, the instrument will always be covered.

The MGC Simple+ is the future of gas detection – the world’s first ‘NO calibration’ portable multi-gas detector.

NO calibration. NO charging. NO cost.

Contact us to find out more.