Blockages in flue liners for gas fires are not the only accessories that may require maintenance to avoid carbon monoxide build-up.
Coal, oil and wood stove pipes are all also capable of becoming blocked and posing a safety risk to homeowners.
The dangers of carbon monoxide are well-recognised but often ignored by homeowners who forget to clean their flue accessories on a regular basis, potentially leaving themselves under threat.
According to chimney safety campaign group Be Carbon Monoxide Aware, excessive condensation in a room where flue accessories are located can be a sign of carbon monoxide build up.
The organisation also recommends looking out for sooting or staining around any appliances, such as flue liners for woodburners.
Lazy yellow or orange coloured flames on gas fires are also a sign of carbon monoxide build-up, but this could also be a sign that an appliance is not working properly. Flames on working appliances should appear crisp and blue.