Should you open windows if carbon monoxide alarm goes off?

Quick Answer

Yes, you should immediately open windows if your carbon monoxide alarm goes off. Opening windows allows fresh air to enter the home, helping to dilute and remove the dangerous carbon monoxide gas. You should also evacuate the home and call emergency services. Never ignore a carbon monoxide alarm.

What is carbon monoxide?

Carbon monoxide (CO) is an odorless, colorless, poisonous gas that is produced when fuels like gasoline, oil, propane, natural gas, wood, or coal are burned. When these fuels do not burn completely, carbon monoxide is created as a byproduct.

CO is dangerous because it binds to hemoglobin in the blood, replacing oxygen molecules. This prevents oxygen from being transported around the body effectively, leading to tissue damage and eventual death from oxygen starvation.

What are the symptoms of carbon monoxide poisoning?

Exposure to high levels of carbon monoxide can cause the following symptoms:

  • Headaches
  • Dizziness
  • Nausea and vomiting
  • Confusion and disorientation
  • Fatigue
  • Shortness of breath
  • Chest pain
  • Visual changes
  • Loss of consciousness

At very high concentrations, carbon monoxide can be fatal within minutes. Those who survive may suffer from neurological damage, memory loss, and permanent heart or brain damage.

What causes high carbon monoxide levels?

Common causes of elevated carbon monoxide levels in the home include:

  • Malfunctioning fuel-burning appliances like furnaces, water heaters, fireplaces, and stoves
  • Blocked chimneys or flues
  • Running a car or generator in an attached garage
  • Burning charcoal or fuel indoors
  • Using gas stoves and ovens for heating

Poor maintenance and lack of proper ventilation can allow CO to accumulate indoors to dangerous levels.

How can you prevent carbon monoxide poisoning?

Here are some tips for preventing carbon monoxide issues in your home:

  • Install CO alarms on every level of the home and near sleeping areas.
  • Have fuel-burning appliances inspected annually by a professional.
  • Make sure chimneys and flues are clean and clear of debris.
  • Never run vehicles or generators indoors, even if doors are open.
  • Never use gas ovens or ranges for heating.
  • Open a window when using a fireplace or kerosene heater.
  • Learn the symptoms of CO poisoning and the difference between CO and smoke alarms.

Taking preventative measures can help keep carbon monoxide from building up and endangering you and your family.

What should you do if the carbon monoxide alarm goes off?

If your carbon monoxide detector sounds an alarm, take the following steps immediately:

  1. Evacuate all occupants from the home, leaving doors and windows open as you exit.
  2. Call 911 from outside the home to report the situation.
  3. Contact your local fire department.
  4. Do not re-enter the home until emergency responders have given the all-clear.

Opening doors and windows as you exit will allow fresh air to enter and begin diluting the carbon monoxide. Never ignore a CO alarm, as the gas can be deadly within minutes at high concentrations.

Should you open all the windows and doors?

Yes, you should open as many doors and windows as possible on your way out if the carbon monoxide alarm activates. This serves two purposes:

  • It allows trapped CO to vent out of the house, lowering concentrations.
  • It allows fresh outdoor air to enter and circulate, further diluting any lingering gas.

The more windows and doors you can open, the better. Open every window and door you have access to as you make your exit.

If it is safe to do so, opening windows and doors on upper levels of the home can be particularly effective, as carbon monoxide rises and tends to accumulate higher up. Opening upper-level windows enables the gas to vent out more quickly.

Should you open windows in winter weather?

Yes, you should still open windows in cold weather if the CO alarm sounds. Although letting in freezing air may be uncomfortable, it is necessary to dilute the toxic carbon monoxide.

Brief exposure to the cold is better than remaining in a building with elevated CO levels, which can rapidly turn deadly. If needed, grab coats, hats and blankets on your way out to stay warm until emergency crews arrive.

Is it safe to ventilate before exiting the home?

No, you should always evacuate immediately when a carbon monoxide detector goes off. Do not delay exiting in order to open doors and windows first.

Carbon monoxide can incapacitate or kill very quickly at high concentrations. The most important step is to get outside to fresh air right away. Openings doors and windows as you make your way out is advisable, but never try ventilating before evacuating.

Should you break windows to ventilate?

Breaking windows to ventilate is not recommended. The priority should be getting out safely, not property damage.

Breaking glass can create hazards as you exit. It may also allow cold air and precipitation into the home, causing additional property damage.

Unless exits are truly blocked, evacuate through standard doors and windows first. Emergency responders can ventilate fully upon arrival by breaking windows if deemed necessary.

How long should you ventilate the home for?

You should not re-enter the home until emergency responders confirm it is safe to do so. Allow professionals with CO monitors to properly ventilate and clear the home before returning.

In most cases, opening doors and windows for 20-30 minutes will sufficiently air out a home enough for short-term entry to retrieve belongings. However, CO levels should always be professionally tested before occupancy can safely resume.

Attempting to judge safety based on ventilation time is risky. CO may be trapped in pockets or continue seeping from sources. The fire department or utility company should confirm safe CO readings across the entire home.

Can you ventilate instead of evacuating?

No, you should never try to simply ventilate the home instead of evacuating. Ventilating does dilute indoor carbon monoxide, but not quickly enough to avoid exposure in an active CO emergency.

Opening windows and doors is not a substitute for evacuation. Lingering in a contaminated home while trying to air it out puts you at severe risk of poisoning.

Leave the building first, then call emergency services to ventilate and clear the home properly with fans and other gear before allowing re-entry. Never attempt to ventilate an actively dangerous CO situation on your own.

What else should you do during a carbon monoxide leak?

In addition to evacuating and calling emergency services when your CO detector activates, take the following steps:

  • Move upwind of the home to avoid lingering gas outdoors.
  • Perform a head count to check that all occupants safely evacuated.
  • Call your gas or utility company to report the incident.
  • Determine the source of the leak, if known, and advise responders.
  • Do not re-enter the building for any reason until officials say it is safe.

Follow all guidance from dispatchers and first responders regarding where to wait and when it is safe to re-enter. Never ignore a carbon monoxide alarm.

Can fans fully remove carbon monoxide?

Using fans alone is not sufficient to remove carbon monoxide from a home. Fans can help circulate and dilute CO as part of a comprehensive ventilation process, but they do not fully eliminate CO.

Even high-powered fans cannot purge all the gas from a home. CO can get trapped in pockets, absorbed into furnishings, and continue leaking from appliances. Professional CO detectors should always be used to confirm safe levels across an entire home after ventilation and before re-occupying.

Fans help speed air exchange during ventilation but should never be relied upon by themselves to make a home safe after a carbon monoxide leak. Evacuation and professional remediation are still required.

Will opening windows stop carbon monoxide alarms?

Opening windows and doors will not immediately stop carbon monoxide alarms from sounding. Alarms will continue sounding until carbon monoxide levels drop below detector thresholds.

It takes time for airflow to effectively reduce CO levels. Alarms may sound for an extended period even with windows and doors open as gas gradually dilutes and vents out.

The only way to fully silence CO alarms is to eliminate the carbon monoxide source and allow fresh air to circulate until safe readings are verified across the entire home. Do not be alarmed if alarms persist even with open windows. Focus on evacuating quickly.

Can you air out a home to avoid evacuation?

No, trying to air out a home instead of evacuating during a carbon monoxide emergency is very unsafe. CO levels can build rapidly to lethal levels before enough ventilation occurs to make a difference.

Immediately evacuate first, then allow responders to ventilate thoroughly with professional equipment like exhaust fans. Never try ventilating yourself instead of getting out quickly. You will pass out and die from carbon monoxide poisoning before you can sufficiently air out a contaminated home simply by opening windows.

Err on the side of safety if a CO alarm activates and exit immediately, no matter how inconvenient. The risk of staying behind to ventilate is much too high.


Always open doors and windows on your way out if a carbon monoxide detector sounds. Ventilating helps remove the toxic gas from the home and allows breathable air to enter. However, evacuating quickly must remain the top priority. Never delay exiting in order to ventilate first. Leave immediately and call emergency services to properly clear the home of CO using detectors and fans before re-entry. Ignoring a carbon monoxide alarm can prove fatally foolish. When in doubt, get out.

Leave a Comment