Carbon Monoxide and Your Furnace

The first cold nights of the season are when furnaces start running for months, and it's the right time to think about carbon monoxide (CO). You can't see it, smell it, or taste it, which is why working CO alarms and a well-maintained furnace matter so much.

The good news: CO problems are preventable. This guide explains how a furnace can produce CO, what warning signs to watch for, where to place alarms in your home, and how a yearly tune-up from Bloomington Heating & Air helps keep your family safe all winter.

How a Furnace Can Produce Carbon Monoxide

Any fuel-burning appliance can release CO when it isn't burning or venting properly. A gas furnace is designed to send combustion gases safely outside, but a few problems can interrupt that:

• A cracked heat exchanger. The heat exchanger keeps combustion gases separate from the air that warms your home. A crack can let those gases escape into your living space. Older systems are more likely to develop cracks, so it's worth reading about common issues with older furnaces.
• Blocked or damaged venting. Flue pipes and outdoor intake and exhaust vents must stay clear. Snow, ice, leaves, or a nest can block them.
• Poor combustion. Dirty or misadjusted burners can burn inefficiently and produce more CO.
• Other fuel-burning equipment. Water heaters, fireplaces, gas stoves, and garage heaters can also release CO. Never run a generator, grill, or camp stove indoors or in a garage. If you lose power, our guide to alternative heating options for winter power outages covers safer choices.

A well-maintained furnace in good condition is very safe. Most problems start small and can be caught early with regular inspection.

Warning Signs of a Carbon Monoxide Problem

Because CO is invisible, your alarms are your first line of defense. Other clues can also tell you something is wrong.

Signs in your body

CO poisoning can feel like the flu, but without a fever or body aches. Watch for:

• Headache or dizziness
• Fatigue or weakness
• Nausea or vomiting
• Shortness of breath
• Confusion

A key clue is timing: symptoms often ease when you leave the house and return when you come back. Pets may seem unwell too. Children, older adults, and pregnant people are especially vulnerable.

Signs around your furnace

• A yellow or orange burner flame instead of a steady blue one
• Soot or dark streaks near the furnace or vents
• Rust or unusual moisture around the furnace or flue
• A furnace that short cycles, makes new noises, or seems to be struggling. See our guide to signs of a malfunctioning furnace.

If your CO alarm sounds

1. Get everyone, including pets, outside to fresh air right away.
2. Call 911 from outside, especially if anyone has symptoms.
3. Don't go back in until emergency responders or your gas utility say it's safe.
4. Once it's safe, have the source found and fixed before you use the furnace again. Our emergency heating repair team is available 24/7.

Where to Put Carbon Monoxide Alarms in a Minnesota Home

Minnesota requires working CO alarms in homes. State guidance calls for an alarm within 10 feet of every bedroom, and every level with sleeping areas needs one. Here's how to get it right:

• Place alarms near bedrooms. Measure from the bedroom door. A wall or closed door between the alarm and the bedroom doesn't count.
• Install them properly. Plug-in alarms should go in an outlet without a switch, and battery alarms should be mounted rather than left on a shelf. Follow the manufacturer's instructions, including where not to place them.
• Test monthly. Press the test button on each alarm.
• Change batteries every year. A simple habit is to do it when you change your clocks in the fall. Hardwired alarms need fresh backup batteries too.
• Replace alarms on schedule. Check the date on the back of each unit. State guidance says to replace alarms every 5 to 7 years, and some newer models are rated longer, so follow your owner's manual.

One working alarm on each level near the bedrooms is a small investment that protects everyone in your home.

How a Yearly Furnace Tune-Up Helps Prevent CO Problems

State health and fire safety officials recommend having fuel-burning heating equipment professionally inspected every year before cold weather arrives. That's exactly what a furnace tune-up in Bloomington, MN is for.

During a tune-up, your technician inspects the parts that matter for safe, efficient operation, such as the heat exchanger, burners, venting, and safety controls, and cleans or adjusts what needs attention. Catching a worn part or a blocked vent early is far easier, and safer, than dealing with a breakdown in January.

Here's how to get ahead of winter:

• Schedule your tune-up this fall. Our heating maintenance service makes it easy, and our post on scheduling maintenance now to avoid freezing nights later explains why timing matters.
• Join the Comfort Savings Plan. Our planned maintenance membership keeps your heating and cooling systems in expert hands year-round, and more than 700 households already trust it.
• Keep outdoor vents clear. After a snowfall, check that your furnace's intake and exhaust vents aren't buried or blocked.
• Replace your filter on schedule. Better airflow helps your system run the way it should. See our fall HVAC system checklist for more.

If your furnace is older and keeps needing repairs, it may be time to look at replacement. Our guide to signs you need a new furnace can help, and we offer financing to make an upgrade easier.