How to Spot Carbon Monoxide Problems Early

Carbon monoxide (CO) is a gas you can’t see or smell, but at high levels it can make people very sick or kill within minutes. The Centers for Disease Control and Prevention (CDC) describes it as an odorless, colorless gas that can cause sudden illness and death if inhaled.

In Washington, the Department of Health (DOH) reports that more than 20 people die each year from unintentional CO poisoning, with most incidents in fall and winter.

Let’s examine what to look for and what to do in case you suspect CO poisoning.

What CO is and where it comes from

CO is produced any time fuel burns—gasoline, diesel, natural gas, propane, oil, kerosene and even wood and charcoal. The U.S. Environmental Protection Agency (EPA) lists common household sources as furnaces, gas water heaters, gas stoves and ovens, fireplaces, wood stoves, portable generators, and vehicles in attached garages.

Because CO has no smell or color, a room can feel “normal” while levels are climbing. Risk is highest in enclosed or semi-enclosed spaces: tightly sealed homes, garages, basements, campers, and RVs. Many serious cases happen when appliances are malfunctioning or used in ways they weren’t designed for, especially during power outages.

Symptoms to watch for

At very high levels, carbon monoxide can cause people to lose consciousness and die, but it often starts with symptoms that look a lot like the flu. Headache, dizziness, fatigue, nausea, vomiting, chest pain, and confusion are all common early signs. What makes CO tricky is that these symptoms usually come on gradually and don’t feel dramatic—at least at first.

There are a few warning patterns that point to carbon monoxide instead of a virus. If several people or pets in the same home get sick at the same time, that’s a major red flag. Symptoms that improve when someone steps outside and return when they go back in are another strong indicator. And if the symptoms appear or worsen while a fuel-burning appliance, vehicle, or generator is running, carbon monoxide should be suspected immediately.

What to do if you suspect CO

If you think carbon monoxide might be the problem, treat it as an emergency. The first step is to get everyone—people and pets—into fresh air right away. Don’t stop to investigate or try to locate the source. Once you’re safely outside, call 911 and tell the dispatcher you suspect carbon monoxide. Fire and EMS crews have the equipment to check CO levels, ventilate the space, and determine when it’s safe to re-enter. After that, get checked by a medical professional. Health-care providers can test for CO exposure and provide the appropriate treatment.

If you have questions that don’t rise to the level of calling 911, the Washington Poison Center can still help. Their specialists are available 24/7 at 1-800-222-1222 to offer guidance, answer concerns, and help you figure out next steps.

How to prevent CO problems

Using fuel-burning equipment correctly is one of the most important ways to prevent carbon monoxide problems. Furnaces, chimneys, and other fuel-burning appliances should be inspected by a qualified technician at least once a year, and gas stoves or ovens should never be used to heat a home under any circumstances.

It’s also essential to be strict about vehicles and engines. A car or truck should never idle in an attached garage—even if the garage door is open—and gasoline-powered tools, including generators, should never run in garages, basements, crawlspaces, or any other enclosed area where fumes can build up.

Finally, always keep grills and camp stoves outside. The EPA warns against using charcoal grills, barbecues, or camp stoves indoors, inside garages, or in tents and enclosed porches, because even a short period of use can allow CO to accumulate to dangerous levels.

CO alarms and generators

CO alarms are your early-warning system. EPA and national safety groups recommend having CO alarms on every level of your home and outside each sleeping area. Washington rules now require CO alarms in most residences.

Test alarms regularly, replace batteries as needed, and swap out the whole unit when it reaches the end of its rated life.

Portable generators deserve special attention. DOH’s guidance during outages: only use generators outdoors and far from open windows and vents. EPA adds that generators should never be used inside homes or garages and should be placed at least 20 feet from buildings, with exhaust pointed away.

The Portable Generator Manufacturers’ Association (PGMA) encourages people to choose generators that meet the ANSI/PGMA G300 standard, which requires built-in CO sensors that shut the unit down if CO levels around it get too high. That technology is a backup, not an excuse to move the generator closer.

When in Doubt, Get Out

Carbon monoxide is dangerous because it gives no warning—no odor, no color, no irritation. It can build up quietly in homes, garages, and enclosed spaces, especially when fuel-burning appliances or generators are used incorrectly. The early symptoms can look like the flu, but patterns like multiple people getting sick at once, symptoms that improve outdoors, or illness that appears while a fuel-burning device is operating are strong signs something more serious is happening.

First responders have the tools to check CO levels and ensure the environment is safe, and medical professionals can evaluate and treat anyone who’s been exposed. Quick action saves lives—yours, your family’s, and your neighbors’.

If you ever notice these symptoms and suspect carbon monoxide could be involved, don’t wait. Get everyone outside into fresh air immediately and call 911.