What should I check if my furnace is blowing cold air?
If you smell gas or a carbon monoxide alarm is sounding, leave the house and call your gas utility or 911 from outside. If the air is safe, check the filter: ENERGY STAR says a dirty one makes the system work harder and should be checked once a month.
If you smell gas or a carbon monoxide alarm is sounding, leave the house and call your gas utility or 911 from outside. What to do when the furnace is not working is the full order, including the pipe steps if the air is clear. Duluth has that city's gas emergency number.
What the Department of Energy says the furnace does
The Department of Energy HVAC guide says most furnaces heat air by burning gas, oil, or propane, and some use electricity to heat an element. The furnace burner sits in the air handler box with a fan. The fan blows the heated air into supply ducts, and return ducts bring air back to be heated again.
A dirty filter
ENERGY STAR says a dirty air filter will cause the heating and cooling system to work harder to distribute air. That can raise energy costs and damage the equipment. Check the filter once a month in the furnace. If it is dirty, clean a reusable filter or change a replacement filter. Before you pull the filter, that page says to turn off the furnace, air conditioner, and fan at the thermostat, the circuit breaker panel, or a switch. That shutoff is for changing the filter.
The EPA lists worn or poorly adjusted furnaces, and a blocked or disconnected flue, among carbon monoxide sources. If you smell gas or a carbon monoxide alarm sounds, leave. The CPSC says not to look for the source. Why won't my furnace turn on? covers a dirty filter that can shut the air handler down, and generator safety during an outage.
Sources
- Department of Energy Building America: Energy Renovations, HVAC guide for homeowners (PNNL, August 2011, PDF)energy.gov
- ENERGY STAR: How to keep your HVAC system working efficientlyenergystar.gov
- CPSC: Carbon Monoxide Questions and Answerscpsc.gov
- EPA: Carbon Monoxide's Impact on Indoor Air Qualityepa.gov
- MidAmerican Energy: natural gas safetymidamericanenergy.com
- Minnesota Energy Resources: Natural gas safety basicsminnesotaenergyresources.com
Who wrote and checked this page
- Written by
- Cold House Fix editorial staff. Who runs this site
- Facts checked
- , by the Cold House Fix editorial staff, against the sources listed on this page.
- Licensed professional
- None. No licensed heating contractor has checked this page.
Ask for a call about the furnace.
If you smell gas or a carbon monoxide alarm is sounding, leave the house and call your gas utility or 911 from outside. Asking for a call does not hire a company.