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, and emergency call-out rates apply. More seriously, the first burn of the season is when problems that developed over the summer reveal themselves, and some of those problems involve combustion products.

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 for blockage, bird nests, corrosion or disconnection. 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. Press and hold each one.
5. Run the heating for fifteen minutes. Do it on a mild day with a window open. Expect a burning dust smell for a few minutes as summer dust burns off the heat exchanger.
6. Watch the burner flame. It should be crisp and blue. Yellow, orange or lazy flames mean 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 flickering burner flame rather than a steady blue one
• A burning smell that persists beyond the first few minutes
• Banging, rumbling or booming on ignition, which can indicate delayed 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
• Closing registers in unused rooms on a forced air system, which unbalances airflow and can raise pressure enough to cause problems

• Do it in September or early October in the northern hemisphere, before contractors get busy
• Systems more than fifteen years old warrant the professional service every year without exception
• A house left empty over summer needs a more careful first burn

Yellow flames, soot, persistent smells, repeated lockouts or any CO alarm activation mean stop using the system and call a qualified technician. Do not keep resetting a system that keeps locking out: the lockout is a safety device doing its job.