Carbon Monoxide in Your Home: Symptoms, Sources, and How to Stay Safe

If your carbon monoxide alarm is going off right now: get everyone, pets included, outside into fresh air immediately. Then call 911 or the fire department from outside. Don't go back in until responders tell you it's safe. Once the house is clear, call us at (928) 499-0698 and we'll find and fix the source.

What is carbon monoxide?

Carbon monoxide (CO) is a colorless, odorless, tasteless gas produced whenever a fuel such as natural gas, propane, wood, gasoline, or charcoal burns incompletely. When you breathe it in, CO takes the place of oxygen in your blood. Low levels cause headaches and fatigue; high levels can cause unconsciousness and death within minutes. Because you can't see or smell it, a working CO alarm is the only reliable warning.

What are the symptoms of carbon monoxide poisoning?

Early CO poisoning is easy to mistake for the flu. Watch for:

• Dull headache, often the first symptom
• Dizziness, weakness, or unusual sleepiness
• Nausea or vomiting
• Shortness of breath or chest pain
• Confusion or blurred vision

Three patterns point to CO rather than a virus: there's no fever, several people (or pets) in the house feel sick at the same time, and symptoms ease when you leave home and return when you come back. If you notice any of those, get outside and call 911.

What causes carbon monoxide in a house?

Any appliance or engine that burns fuel can produce CO. The most common household sources we find are:

• Gas or propane furnaces, especially with a cracked heat exchanger, a blocked or disconnected flue, or a burner that's out of adjustment
• Gas water heaters with poor venting or back-drafting
• Gas ranges and ovens, particularly when used to heat a room
• Fireplaces and wood stoves with a closed damper or a dirty chimney
• Cars, generators, and small engines running in or near an attached garage

Why is CO risk highest in Prescott during heating season?

From October through April, Prescott-area furnaces run daily after sitting idle all summer, and windows stay shut. Flues can collect debris or nests, and a heat exchanger that was fine last spring can crack as it ages. Our elevation matters too: at roughly 5,400 feet, gas appliances must be set up for high altitude. A burner adjusted for sea level can burn rich and produce more carbon monoxide. That's why we run a combustion test, not just a visual check, on every fall heating checkup.

Where should carbon monoxide detectors be installed?

• Outside every sleeping area, close enough to wake people behind closed doors
• On every level of the home, including a finished basement
• Near the door from an attached garage
• Not right next to a furnace, water heater, or range, and not in a steamy bathroom. Follow the spacing in the alarm's instructions.

Combination smoke/CO alarms are fine. Press the test button monthly. CO sensors wear out, so replace the alarm every 5 to 10 years (check the date on the back). An end-of-life chirp means it's time.

What carbon monoxide level is dangerous?

CO is measured in parts per million (ppm). Home alarms built to the UL 2034 standard are designed to sound before most healthy adults would feel symptoms: within 60–240 minutes at 70 ppm, 10–50 minutes at 150 ppm, and 4–15 minutes at 400 ppm. That's why a standard alarm won't react to brief, very low readings. If anyone in the home is pregnant, elderly, an infant, or has heart or lung disease, ask us about a low-level CO monitor that displays readings below the alarm threshold.

How does an HVAC technician check for carbon monoxide?

1. Combustion analysis. We measure CO and oxygen in the flue gas to confirm the burner is clean and properly adjusted for altitude.
2. Heat exchanger inspection. We look for cracks or rust-through that could let flue gases mix with the air you breathe.
3. Venting and draft test. We confirm the flue is intact, properly sloped, and pulling exhaust out of the house.
4. Ambient CO readings. We sample the air near appliances and in living spaces.

If we find a problem, we explain it, show you what we found, and quote the fix before we touch anything. See our AC & furnace repair service for details.

How do I prevent carbon monoxide problems?

• Get your furnace inspected every year before heating season. A service agreement makes that automatic.
• Never run a portable generator in a garage, carport, or near a window. A permanently installed standby generator sits outdoors and is wired in safely. See our generator guide.
• Never heat your home with a gas oven or range.
• Keep exterior vents and flues clear of snow, leaves, and nests.
• Consider going electric. A heat pump heats without burning fuel, so it removes the furnace as a CO source entirely.

Not sure when your furnace was last checked? Get in touch or book online. One crew handles both the HVAC and the electrical side.