Carbon monoxide and winter heating safety: a checklist from Washington State DOH

By Jason Dearmin · Last reviewed November 14, 2026 · How we check facts

Symptoms

Washington DOH lists headache, weakness, dizziness, confusion, fatigue and nausea. It says CO can build up so quickly that victims are overcome before they can get help, and that it can cause permanent brain damage or chest pains or heart attacks in people with heart disease.

Prevention rules

• Never burn charcoal inside homes, tents, campers, vans, trucks, garages or mobile homes.
• Do not burn charcoal in a fireplace.
• Never use gasoline-powered equipment indoors.
• Never use a gas oven to heat your home, even for a short time.
• Never idle a car in a garage, even with the door open.
• Never sleep in a room while using an unvented gas or kerosene heater.
• Make sure chimneys and flues are in good condition and not blocked.
• Never cook or heat inside on a charcoal or gas grill.
• Install battery-operated or battery-backup CO alarms. DOH says alarms may provide additional protection but should not replace the other steps.

Heating equipment and CO

Furnace safety switches exist to prevent unburned gas or exhaust from entering the home. Carrier says the flame sensor is a safety component that must never be bypassed, and notes that bypassing it can cause carbon monoxide poisoning or explosion. Pressure and rollout switches (see Carrier code 32 and Trane 3 flashes) prove that exhaust is moving out of the house. Never defeat them.

If you suspect poisoning

Move the person to fresh air immediately and take them to an emergency room, telling them you suspect carbon monoxide poisoning. Call 911 if anyone is unconscious or an alarm is sounding and symptoms are present.

For generators, see furnace after a power outage and generator safety.

Frequently asked questions

Can I run a portable generator in my garage with the door open?

No. Washington DOH says never use a portable generator in a garage, carport, basement or crawl space, even with ventilation, because opening doors and windows will not prevent CO buildup.

Do CO alarms replace other precautions?

No. DOH says alarms may provide additional protection but should not replace the other prevention steps.

Sources

• Carbon Monoxide Safety (Washington State Department of Health)
• Generator Use During a Power Outage (Washington State Department of Health)
• Furnace Flame Sensor: What It Is, Why It Fails, and How to Fix It (Carrier)

Safety note: this page is general information drawn from the sources above. Gas, combustion and line-voltage repairs belong to a licensed professional. Your own equipment's label and manual take priority over anything here. Read the full disclaimer.