How Do Gas Detectors Work?

Both at home and at work, gas detectors help keep us safe. As well as being a legal requirement in some environments, they’re installed to protect against the potentially fatal effects of gases like carbon monoxide, natural gas, methane, and ammonia.

Gas detectors work by measuring the amount of a certain gas in the surrounding air and sending an alert when the concentration level of this substance gets too high. Depending on the specific type of gas, each detecting device will work slightly differently. 

This guide will explain exactly how gas detectors work, outline how they’re calibrated, and give advice on finding the right one for your needs.

Getting the right gas detection equipment relies on knowing which gas you want to detect and the environment you need to protect. For example, gas leak detectors help to find the source of released fumes while gas analysers or gas meters give readings of a specific substance in the surrounding atmosphere.

Alongside choosing the right type of gas detector, having accessories such as mounting sockets, probes, and cases will help improve the accuracy of each measurement. Calibrating the sensor of choice regularly, ideally every six to twelve months, according to the manufacturer’s instructions, will also ensure your detector is truly keeping people safe.

Every type of detector or analyser is designed to measure particular types of gas, be they domestic or industrial gas detectors. This means they have different types of sensors. The main types of gas-detecting sensors are:

• Catalytic: these use a catalytic wire made from elements that oxidise in the presence of combustible gases in the atmosphere alongside a wire that doesn’t. As the one wire oxidises, resistance in it increases. The difference between the resistance of the two wires triggers a response in the detector's circuit and raises the alarm
• Infrared: these types of detectors have a light transmitter and receiver. When combustible gases pass between the transmitter and receiver, it changes the nature of the light. This change is picked up by the receiver and an alarm is triggered
• Electrochemical: these use electrodes to detect toxic gases in the air. When certain gases come into contact with the sensor electrodes, a chemical reaction occurs and triggers the flow of electrons. The current this generates is measured and a level of gas in the air is given on the detector
• Metal oxide semiconductors: otherwise known as MOS detectors, they contain a film that has electrons flowing freely through it when heated. In the presence of oxygen, this flow is restricted. Yet when the level of another gas is high, the flow is increased, as is the resistance in the detector, triggering an alarm

Depending on the specific type of gas you’re trying to detect and the particular environment you’re measuring it in, different gas detectors will be appropriate.

Carbon monoxide and natural gas risk safety in two different ways. When inhaled, carbon monoxide damages red blood cells and stops the natural flow of oxygen around the body and organs. After extended exposure, this can start to cause symptoms such as headaches and nausea and even lead to death.

In contrast, natural gas is highly flammable and can cause explosions or fire hazards when present in high concentrations. For these reasons, both gases are a danger in homes and commercial environments and can’t be detected by the same sensors.

Electrochemical and MOS sensors are best for detecting carbon monoxide as this gas triggers chemical reactions in the detectors. Meanwhile, catalytic and infrared sensors detect an increase in levels of natural gas by monitoring the movement of air. This means carbon monoxide detectors won’t be triggered by an increase in levels of natural gas.