01A carbon monoxide alarm sounds when the furnace is running
Leave the house with everyone and call 911 from outside. After responders clear the home, we inspect the furnace, venting and heat exchanger to find the source, repair it, and confirm carbon monoxide readings are clear at the furnace and every supply register before the furnace runs again. Carbon monoxide is colorless and odorless, and exposure can cause headaches, dizziness, nausea, confusion and, at high levels, death.
02A rotten-egg gas smell near the furnace or in the house
Get everyone out without flipping switches, then call Xcel Energy's gas emergency line or 911 from outside. Once the utility has made the area safe, we inspect the furnace's gas valve, connections and burners and repair whatever caused the leak. A gas leak can ignite from a light switch, phone or appliance spark, so staying inside to investigate is dangerous.
03Flames visible outside the burner area or a tripped rollout switch
Turn the furnace off at the thermostat and the service switch, and do not keep resetting the rollout switch. We check for a blocked heat exchanger or flue, a cracked heat exchanger, and venting problems, and the furnace stays off until it can run safely. Flame rollout can scorch wiring and nearby materials and is a fire risk if the furnace keeps running.
04No heat overnight during a hard freeze
Open sink cabinets on exterior walls and let faucets drip while we diagnose the furnace. We follow the startup sequence to find the failed part, often an igniter, flame sensor or pressure switch, and repair it so the house warms back up. At single-digit temperatures, pipes in exterior walls and crawlspaces can freeze and burst, causing water damage far more costly than the furnace repair.