Yes, natural gas heaters can cause carbon monoxide poisoning if they are improperly installed, poorly maintained, or used in poorly ventilated spaces, as they can produce harmful CO gas when combustion is incomplete.
Yes, natural gas heaters can cause carbon monoxide (CO) poisoning if they malfunction, are improperly installed, or lack proper ventilation. CO is a silent killer—odorless, colorless, and deadly in high concentrations. Understanding the risks and prevention methods is critical for safe heating.
How Natural Gas Heaters Produce Carbon Monoxide
Natural gas heaters burn fuel to generate heat. When combustion is incomplete due to insufficient oxygen or faulty components, CO is produced. Common scenarios include:
- Cracked heat exchangers: Metal fatigue from repeated heating/cooling cycles can create leaks.
- Blocked vents: Bird nests, debris, or snow can obstruct flues, trapping CO indoors.
- Improper ventilation: Unvented heaters (like some ventless models) release combustion byproducts directly into living spaces.
Danger Levels of CO Exposure
The CDC and ASHRAE define hazardous CO concentrations:
| CO Level (ppm) | Exposure Time | Effects |
|---|---|---|
| 1-9 | Safe for most people | No symptoms |
| 35+ | 8 hours | Headaches, nausea |
| 200+ | 2-3 hours | Disorientation, unconsciousness |
| 800+ | 45 minutes | Fatal |
Signs of CO Poisoning
Symptoms often mimic flu or food poisoning:
- Dull headache
- Dizziness
- Nausea/vomiting
- Confusion
- Blurred vision
Pets may show signs first—lethargy or vomiting. If multiple household members (or pets) experience symptoms simultaneously, evacuate immediately and call 911.
Preventing CO Poisoning from Gas Heaters
1. Proper Installation & Maintenance
- Hire licensed professionals for installation (see gas heater installation guide).
- Schedule annual inspections—technicians check heat exchangers, burners, and venting.
- Clean vents regularly to prevent blockages.
2. Use CO Detectors
- Install UL-listed detectors on every floor, near sleeping areas.
- Choose models with 35 ppm sensitivity (not just 75 ppm alarms).
- Replace batteries annually; units expire every 5-7 years.
3. Ventilation Best Practices
- Never use unvented heaters in bedrooms or bathrooms.
- Ensure vented gas heaters have clear outdoor exhaust paths.
- Open windows slightly when using older heaters.
Alternatives to Combustion Heaters
Eliminate CO risks entirely with:
- Electric heaters: Ceramic or infrared models (Energy.gov recommends).
- Heat pumps: Transfer heat instead of burning fuel.
- Hydronic systems: Use hot water circulated through radiators.
Emergency Response
If your CO alarm sounds:
- Evacuate everyone (including pets) to fresh air.
- Call emergency services—even if symptoms subside outdoors.
- Do not re-enter until professionals declare the area safe.
For persistent issues like pilot light failures, troubleshoot gas heater problems with expert guidance.
