CARBON monoxide is known as "the silent killer" and safety experts advise householders to have a special alarms and regularly service their fuel appliances.
Since October 2012, newly-built homes in the north have been required to have a carbon monoxide alarm fitted by law.
The Health and Safety Executive advice states: "CO is produced by the incomplete combustion of solid, liquid and gaseous fuels. It is a highly poisonous gas which is impossible to see, taste or smell.
"The best way to protect against carbon monoxide is to make sure all fuel-burning appliances are properly installed by recognised and established engineers, and serviced by competent companies or individuals - at least once a year."
The guidance adds: "Don’t forget that chimneys and flues should also be inspected annually and swept, if required, by a registered technician."
Symptoms of carbon monoxide poisoning can be confused with food poisoning, flu or viral infections.
The HSE warns: "Symptoms to look out for include headaches, nausea, breathlessness, dizziness, collapse or unconsciousness."
The regulator advises that if carbon monoxide is suspected, all appliances should be turned off immediately, windows should be opened, and the person concerned should stay outside and seek medical help.
