How often should you check your heating before winter?

Testing heat early avoids a no-heat emergency on the first cold night.

A heating system that fails on the first cold night joins a queue. More seriously, the first burn of the season is when problems that developed over the summer reveal themselves, and some of those problems involve carbon monoxide, which can only be detected with an alarm.

1. Replace the filter. Start the season clean. A filter left in since spring is already partly loaded.
2. Clear the area around the unit. Remove anything stored against the furnace over summer. Combustion appliances need clearance and combustion air, and storing boxes against them is both a fire risk and an airflow problem.
3. Check the flue and vent terminal. Look from the outside for blockage, bird nests, corrosion or disconnection, without dismantling anything. On high-efficiency units check the plastic intake and exhaust terminals outside are clear.
4. Test the CO alarms. Do this now, before the first burn, not after. Use the test button as the manufacturer instructions describe, and replace any alarm that has passed its end-of-life date.
5. Run the heating for fifteen minutes. Do it on a mild day with a window open. A dusty smell for the first few minutes is normal as dust burns off.
6. Look at the burner flame if it is visible. Do not remove covers to see it. The Health and Safety Executive in Britain lists yellow or orange rather than blue flames as a sign of incomplete combustion. If you see that, stop and call a technician.
7. Check every radiator or register. Bleed radiators that are cold at the top. Confirm airflow at every register and that none have been closed off or blocked by furniture.
8. Check the thermostat and its schedule. Fresh batteries and a schedule that matches how the household actually lives.

• A yellow or orange burner flame rather than a blue one
• Soot or yellow or brown staining on or around the appliance
• A pilot light that frequently blows out
• A burning smell that persists beyond the first few minutes
• Banging, rumbling or booming on ignition
• The system starting and stopping repeatedly without reaching temperature
• Cold radiators, or registers with no airflow
• Any CO alarm activation at all

• Testing it for the first time on the coldest night of the year
• Storing paint, solvents or boxes against the furnace over summer and forgetting to move them
• Ignoring a burning smell that lasts more than a few minutes
• Treating the seasonal check as a substitute for the professional service, when it is a complement to it
• Leaving registers closed or blocked by furniture after the summer

• Do it in September or early October in the northern hemisphere, before contractors get busy
• The US Consumer Product Safety Commission advises a professional inspection and service of the heating system every year, whatever its age
• A house left empty over summer needs a more careful first burn

Yellow or orange flames, soot, persistent smells, repeated lockouts or any CO alarm activation mean stop using the system and call a qualified technician. If a CO alarm sounds, get everyone out into fresh air first. Do not keep resetting a system that keeps locking out: the lockout is a safety device doing its job. Anything involving the gas supply, the burner or the flue is work for a licensed professional, not a homeowner.