Carbon Monoxide & Your Gas Fireplace: What Every Ohio Homeowner Must Know

Carbon monoxide (CO) is called the "silent killer" for good reason. It's colorless, odorless, and can incapacitate you before you realize anything is wrong. While modern gas fireplaces are designed with multiple safety features to prevent CO exposure, problems can and do occur — especially in fireplaces that haven't been properly maintained.

This guide covers everything Northeast Ohio homeowners need to know about carbon monoxide and gas fireplaces.

Yes. All gas-burning appliances — including gas fireplaces — produce carbon monoxide as a byproduct of combustion. Under normal operating conditions, a properly functioning and vented gas fireplace produces very small amounts of CO that are safely vented outside your home.

The danger arises when something goes wrong with the combustion process or the venting system, causing CO to accumulate indoors.

This is the most common cause of CO exposure from gas fireplaces. If the vent pipe is blocked, disconnected, cracked, or improperly installed, combustion gases — including CO — can spill back into your living space instead of being exhausted outside.

Common venting issues:

• Bird nests or debris blocking the vent termination cap
• Ice dams blocking the vent in winter (common in Northeast Ohio)
• Disconnected or improperly sealed vent joints
• Cracked or deteriorated vent pipe
• Negative pressure in the home drawing combustion gases back inside

When a gas fireplace doesn't receive enough oxygen for complete combustion, it produces more CO. This can happen due to:

• Clogged burner ports
• Improper gas pressure
• A dirty or malfunctioning burner assembly
• Restricted air supply

Warning sign: If your flames are predominantly yellow or orange instead of blue with yellow tips, incomplete combustion may be occurring.

In some fireplace designs, a cracked heat exchanger can allow combustion gases to mix with room air. This is more common in older units.

Vent-free gas fireplaces are designed to burn so cleanly that they don't require venting. They include an Oxygen Depletion Sensor (ODS) that shuts off the unit if oxygen levels drop. However, they're not recommended for bedrooms, small spaces, or homes with poor air circulation — and they should never be used as a primary heat source for extended periods.

Carbon monoxide poisoning symptoms are often mistaken for the flu — without the fever. If multiple people in your home experience these symptoms simultaneously, especially when the fireplace is running, treat it as a CO emergency:

• Headache (often the first symptom)
• Dizziness or lightheadedness
• Nausea or vomiting
• Shortness of breath
• Confusion or disorientation
• Chest pain
• Loss of consciousness (severe exposure)

If you suspect CO poisoning:

1. Get everyone out of the house immediately
2. Call 911 from outside
3. Do not re-enter until emergency responders clear the building
4. Seek medical attention even if symptoms seem mild

This is non-negotiable. Every home with a gas fireplace should have CO detectors:

• On every level of the home
• Within 10 feet of each bedroom
• Near the fireplace (but not directly above it — heat can affect readings)

Replace CO detector batteries annually and replace the entire unit every 5–7 years (CO sensors degrade over time).

Ohio law requires CO detectors in all new residential construction and in homes with fuel-burning appliances.

A professional annual inspection is your best defense against CO exposure. A qualified technician will check your venting system, burner assembly, and all safety controls to ensure everything is functioning correctly.

Keep the area around your fireplace's air intake and exhaust vents clear. Never store items near the vent termination on the exterior of your home, and check it seasonally for debris or ice buildup.

Some gas fireplaces require electricity to operate the blower and controls. If your fireplace is designed to operate only with the blower running, using it without power could affect combustion air circulation.

If you have a vent-free fireplace, crack a window slightly when it's operating to ensure adequate fresh air supply.

A properly installed, regularly maintained gas fireplace is a safe appliance. The key words are "properly installed" and "regularly maintained." Annual inspections, working CO detectors, and prompt attention to any warning signs are the three pillars of gas fireplace safety.

If your CO detector goes off, your flames look wrong, or you smell something unusual near your fireplace, don't wait. Call Ohio Gas Fireplace at 216-282-1995. We offer emergency service throughout Northeast Ohio.

Your family's safety is worth the call.