Carbon Monoxide Safety for Iowa Homes: Furnaces, Water Heaters and Detectors

Iowa houses get sealed up tight from October to April. The windows stay shut, the furnace runs for hours a day, and every fuel-burning appliance in the basement shares your air. This guide covers what to do if a CO alarm sounds, where carbon monoxide comes from, and where detectors belong. It’s standard safety guidance; in an emergency, 911 comes first.

What should I do if my carbon monoxide alarm goes off?

1. Get everyone out now, pets included. Don’t stop to open windows, find the source or shut off the furnace.
2. Call 911 from outside or from a neighbor’s house. If you also smell gas, call your gas utility’s emergency line from outside too.
3. Tell the dispatcher if anyone feels sick.
4. Stay out until the fire department says it’s safe. Their meters will tell them. Your nose won’t, because CO has no smell.
5. Don’t restart the appliance until it’s been checked. Once responders clear the house, call us at (515) 494-5483. We answer 24/7, and we’ll find the source before anything gets turned back on.

Don’t hit the silence button, decide it’s a false alarm and go back to bed. Learn your alarm’s sounds now, while it’s quiet. A single chirp every minute or so usually means a low battery or an end-of-life warning. A full alarm is loud and repeating; on most models it’s four quick beeps and a pause. The label on the back will tell you which pattern yours uses.

Where does carbon monoxide come from in an Iowa home?

CO is a byproduct of burning fuel: natural gas, propane, gasoline, wood. Every fuel-burning appliance makes some, and the venting is what carries it outside. Trouble starts when the venting fails or the burn goes wrong.

A furnace with a cracked heat exchanger

The heat exchanger is the metal wall between the burner flames and the air blowing through your ducts. After enough heating seasons, especially years of running with a clogged filter, it can crack. A crack can let combustion gases into the air stream. We check for this on every tune-up, and if we find one, we shut the furnace down and show you what we found.

A water heater that’s backdrafting

A gas tank water heater with a metal flue relies on warm exhaust rising up the chimney. If the flue is blocked, disconnected or the chimney is deteriorating, exhaust spills back out at the top of the tank. A setup we see often in older metro homes: the furnace was replaced with a high-efficiency unit that vents out the side wall, leaving the water heater alone in a chimney sized for two appliances. That flue can stay too cool to draft well, so it needs to be looked at whenever a furnace is changed.

Blocked flues and vent pipes

Bird nests, fallen chimney tile, a vent pipe knocked loose during storage-room shuffling, and in winter, snow and ice packed against the white PVC pipes of a high-efficiency furnace. Most high-efficiency furnaces shut themselves off when a vent is blocked, but don’t rely on that. Clear the pipes after every drift.

Attached garages, generators and everything else

Warming up a car in an attached garage, even with the big door open, can push exhaust into the house through the mudroom door. Back it out first. After an ice storm or a bad summer storm, portable generators come out. Never run one in a garage, basement or on a porch, and keep it well away from windows, doors and vents, at the distance on the generator’s label. Also on the list: gas ovens used to heat a room, unvented space heaters, and fireplaces or wood stoves with a closed damper or blocked chimney.

Source	What you might notice	What to do
Furnace heat exchanger	Burner flames that flutter or change when the blower starts; soot around the burners	Turn the furnace off and schedule an inspection
Water heater backdraft	Rust, scorch marks or melted plastic at the top of the tank	Have the venting checked before you rely on it all winter
Blocked high-efficiency vent	Furnace quits after a snowstorm; PVC pipes outside packed with snow or frost	Clear them gently by hand; call if it won’t restart
Attached garage	Exhaust smell inside after warming up a car	Start the car with the garage door open and pull it out
Generator	Running anywhere close to the house	Move it out in the open, away from openings

If any of these happen while a CO alarm is sounding, skip the “what to do” column and leave the house.

Why is carbon monoxide a bigger risk in winter?

More burning, less fresh air. Furnaces run long cycles during cold snaps, newer homes are built tight, older homes have been weatherstripped and re-windowed, and nobody opens a window in January. Snow blocks side-wall vents, and it’s also the season for generators and space heaters. That’s why fall is the time for a furnace safety check and a fresh look at your alarms.

What are the symptoms of carbon monoxide exposure?

The common early symptoms are headache, dizziness, nausea, weakness and confusion. They’re easy to mistake for the flu. Clues that it might be CO instead:

• Several people in the house, or the pets, feel sick at the same time.
• Symptoms ease when you leave the house and return when you come back.
• It’s worse when the furnace or another appliance has been running.

Don’t wait for symptoms to act. If the alarm sounds, leave. If anyone has symptoms, tell the 911 dispatcher.

Where should CO detectors go?

• Every level of the house, including the basement.
• Outside each sleeping area, in the hallway near the bedrooms, so the alarm wakes people up.
• Where the manufacturer says. Some mount on the wall, some on the ceiling, and most instructions say not to put them right next to a furnace or water heater, in a garage, or in a steamy bathroom.

Combination smoke and CO alarms are fine. Interconnected alarms, where one sounds and they all sound, are better, especially in split-levels and larger homes where a basement alarm is hard to hear upstairs. Plug-in alarms should have battery backup, because the power goes out right when generators come out.

How long do carbon monoxide detectors last?

Not forever. The sensor wears out, and depending on the model, most CO alarms are rated for somewhere between 5 and 10 years. The exact replace-by date is printed on the back or side. Many also give an end-of-life signal, a distinct chirp or “END” on the display. When you see it, replace the whole unit; a fresh battery won’t fix a worn-out sensor.

Press the test button once a month. Daylight saving time ends Sunday, November 1, which makes this weekend an easy reminder.

Pro tip: Write the install date on the front of each alarm with a marker. Every time you test it, you’ll see at a glance whether it’s due for replacement.

What does a furnace safety check cover, and what does it cost?

A real tune-up includes a heat exchanger inspection, a combustion and draft check, a look at the venting all the way outside, and a CO reading. Our standard fall tune-up is $129; see what’s included in our furnace tune-up guide.

Service	Typical range
Furnace tune-up with safety check	$99–$150 (ours is $129)
Furnace repair (flame sensor, ignitor, inducer, board, blower)	$150–$800
Furnace replacement, 80% AFUE	$4,000–$5,500
Furnace replacement, 95%+ AFUE	$6,000–$9,000
40–50 gal gas tank water heater replacement	$1,200–$2,000
After-hours dispatch premium (ours)	$75–$125

Planning ranges for the Des Moines metro in 2026; your written quote depends on the equipment, access and what we find on site.

A cracked heat exchanger on an older furnace usually tips the decision toward replacement. Our post on signs your furnace is dying covers how to make that call.

Pro tip: If you’re replacing a furnace with a high-efficiency model, ask what happens to the water heater’s venting. If the answer is “nothing,” ask again.

What can I check myself, and what needs a pro?

On your own: test alarms monthly, replace old ones, keep outdoor vent pipes clear of snow, change the furnace filter, never idle a car in the garage, keep generators outside and well away from the house, and keep storage away from the furnace and water heater.

Leave to us: inspecting the heat exchanger, testing combustion and draft, repairing or rerouting venting, fixing a water heater that won’t draft, and putting any appliance back in service after a CO alarm. If you’re not sure, call (515) 494-5483, day or night. You can read more about our furnace service and 24/7 emergency service.