Methane (CH4) is a colourless, odourless and highly flammable gas, the simplest of the hydrocarbons. It burns readily in air, and a build-up in a confined space such as a mine, sewer or tank can cause a deadly explosion.
Methane is the main component of natural gas and biogas, so it powers heating and cooking in most UK homes as well as industry. It is also a potent greenhouse gas, second only to carbon dioxide in its contribution to global warming.
Is Methane Flammable?
Yes. Methane ignites in air at concentrations between 5% (its lower explosive limit) and 15% (its upper explosive limit), and a spark, flame or hot surface within that band can trigger an explosion. Above 15% there is too little oxygen to burn, but the mixture becomes dangerous again as it disperses and falls back through the flammable range.
Is Methane Dangerous?
Yes, but not as a poison. What people call methane poisoning is really oxygen deprivation: a leak in an enclosed space pushes out breathable air, causing breathlessness, dizziness, confusion and eventually collapse. If you suspect a gas leak, get to fresh air, avoid anything that could spark and call the National Gas Emergency Service on 0800 111 999.
Is There a Workplace Exposure Limit for Methane?
No. Methane has no limit in EH40, the HSE's list of workplace exposure limits, because the harm it does is not poisoning. Instead, detectors measure methane as a percentage of its lower explosive limit, with alarms sounding long before the gas can ignite.
Fun Fact – Around 14.5% of global greenhouse gas comes from life stock fluctuance and manure
Where Do Methane Hazards Occur?
- Farms. Slurry stores and manure pits release methane and other gases at dangerous levels.
- Coal mines and tunnels. Methane trapped in coal seams and rock is released by digging, and mine explosions were the reason the first gas detection instruments were invented.
- Sewers and confined spaces. Rotting organic matter produces methane in sewers, pits and tanks, which is why gas checks come before confined space entry.
- Landfill and waste sites. Decomposing waste generates landfill gas, which is roughly half methane.
- Construction sites. Ground gas migrating through soil and made ground can collect in excavations and basements.
What is Methane Used For?
How Do You Detect Methane?
Methane is detected as a flammable gas, using a catalytic bead, infrared or MPS sensor that reads in %LEL. On site that usually means a portable multi gas detector covering flammable gas, oxygen, carbon monoxide and hydrogen sulphide together, or fixed detectors mounted at high level, because methane is lighter than air and collects at the ceiling.
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Methane Gas FAQs
What does methane smell like?
The familiar gas smell is not methane at all: it is an odorant called mercaptan, added to natural gas so people notice leaks at home. Raw methane on an industrial site gives no warning by smell, so detectors do that job.
What is firedamp?
Firedamp is the miners' name for the flammable gas found in coal seams, which is mostly methane. It caused many historical mine explosions and is still monitored in mining and tunnelling today.