Carbon monoxide (CO) is a colourless, odourless, tasteless, poisonous gas produced by incomplete burning of carbon-based fuels, including gas, oil, wood and coal.
Carbon-based fuels are safe to use. It is only when the fuel does not burn properly that excess CO is produced, which is poisonous.
When CO enters the body, it prevents the blood from bringing oxygen to cells, tissues, and organs.
You can't see it, taste it or smell it but CO can kill quickly without warning.
Visit the Health and Safety Executive website for more information.
More top news
UK defence secretary says so-called Islamic State group will only be defeated by force.
Sheriff's deputies were called to the scene in LA County after residents reported hearing muffled crying.
Further one in eight expect to be aged between 71 and 80 years when they finally stop work, according to survey.