Short answer: Yes. No gas line does not mean no carbon monoxide. Quebec’s building regulator, the Régie du bâtiment du Québec (RBQ), states that conditions inside an ethanol fireplace, such as combustion temperatures that run too high or too low, “can result in incomplete combustion, producing carbon monoxide (CO) and other harmful gases.” Because the fireplace has no chimney, those gases stay in the room. The RBQ calls a CO detector essential. Treat a working CO alarm as a condition of lighting an ethanol fireplace, not an optional extra.
Why “no gas line” is the wrong test
The reasoning most people use goes like this: carbon monoxide comes from gas appliances, an ethanol fireplace has no gas line, so it has no carbon monoxide. The first step is where it breaks.
Carbon monoxide does not come from natural gas or propane specifically. It comes from burning a fuel without enough oxygen, or under poor conditions, so the fuel does not burn all the way. Ethanol is a fuel, and an ethanol fireplace burns it in an open flame with whatever air is in the room.
On paper, ethanol burns cleanly. The RBQ says so directly: “In theory, ethanol is a clean-burning fuel.” Then it adds the part the product pages leave out: in a real fireplace, combustion temperatures that are too high or too low can produce incomplete combustion, and that produces carbon monoxide. The regulator also notes that “although ethanol is similar to the fuel used in fondue burners, the risk is higher due to the larger volumes,” and that with no chimney, toxic substances can build up, “especially in higher-power units.”
If you have read how carbon monoxide forms in ventless gas fireplaces, the mechanism is the same idea with a different fuel: an unvented flame, a closed room, and nowhere for the byproducts to go.
What the evidence actually shows about ethanol and CO
Two kinds of source address this, and they agree on the direction.
The regulator. The RBQ’s ethanol fireplace safety page, which we read on October 2, 2026, names carbon monoxide as a product of incomplete combustion in ethanol fireplaces, calls a CO detector essential, and says the fireplace must be in an adequately sized, well-ventilated room. It adds that “the more powerful the fireplace, the larger the room needed to avoid the risk of poisoning.”
The lab. Researchers at the Fraunhofer Institute for Wood Research (WKI) tested four ethanol stoves with eight liquid and gel fuels. Phys.org’s September 1, 2014 report of that work lists carbon monoxide among the poisonous gases produced, alongside nitrogen dioxide, formaldehyde and benzene. The same report says every device exceeded the nitrogen dioxide guideline the team used, and the researchers advised operating these units only in large, very well-ventilated spaces.
Neither source says every ethanol fireplace produces dangerous CO every time it is lit. Both say it can, and that the room and the unit’s power matter. That is enough to make the alarm non-negotiable.
What a CO alarm does, and what it does not
A CO alarm is the right tool for one specific job: telling you when carbon monoxide in the air has reached a level its standard treats as dangerous. You cannot see, smell or taste CO, so without an alarm the first warning is often the symptoms. The CPSC lists the symptoms of CO poisoning as headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion.
Here is what the alarm will not do:
| Hazard from an ethanol fireplace | Does a CO alarm detect it? |
|---|---|
| Carbon monoxide building up | Yes, that is its job |
| Nitrogen dioxide, which Fraunhofer found above guideline values | No |
| Formaldehyde, also flagged in the Fraunhofer tests | No |
| Falling oxygen in a small, closed room | No |
| A spill or flash fire while refueling | No, that is a smoke alarm and fire safety question |
That table is the information most pages on this question leave out. The alarm covers the one gas that can kill quickly and silently. It is not proof that the air is fine. The Fraunhofer finding on nitrogen dioxide is a reason to keep ventilation generous even when the CO alarm is quiet.
The same gap exists with gas units. Our page on what an oxygen depletion sensor does not catch explains why a safety device on the appliance is not the same as a clean room.
Where the alarm goes and how to treat it
Alarm placement for unvented appliances has its own page, the CO alarm as a condition of use, so we will not repeat all of it here. The baseline comes from the CPSC’s Carbon Monoxide Information Center, read on October 2, 2026: install battery-operated CO alarms, or alarms with battery backup, on every level of the home and outside sleeping areas.
Three habits make the alarm worth having:
- Test it before the first fire of the season, using the test method in the alarm’s own instructions.
- Do not light the fireplace if the alarm is missing, expired or has a dead battery. That is what “condition of use” means.
- Know what to do when it sounds. The CPSC’s instruction is plain: if you suspect CO poisoning, get outside to fresh air immediately, and then call 911. Do not stay behind to deal with the fire.
When the risk goes up
The RBQ ties the poisoning risk to room size and fireplace power. Fraunhofer ties it to ventilation. Put together, the situations where an ethanol fireplace deserves the most caution are predictable:
- A small or closed room. Less air to dilute the byproducts. The RBQ says to avoid installing built-in units in bathrooms and bedrooms.
- A powerful unit or several burners. The RBQ says more power needs a larger room.
- An airtight or newly sealed home. Less natural air exchange. Our page on ventless units in basements and airtight homes explains why the risk changes with the building, not just the appliance.
- Long burns. More fuel burned means more byproducts in the same air.
- The wrong fuel. The RBQ says to use only the ethanol the manufacturer recommends, and never gasoline or gasoline-ethanol blends.
- A household member with a health condition. Whether an unvented flame is appropriate around them is a question for their doctor, asked before the first fire, not after symptoms.
The fireplace should also carry a recognized certification. In Quebec, the RBQ says it must meet ULC/ORD-C627.1-2008. In the United States, the safety standard for this product type is UL 1370. Certification shows the design was evaluated. It does not replace the alarm.
What sellers say, and why it does not settle the question
Several retailers in the search results for this topic say ethanol fireplaces produce little or no carbon monoxide. Some of that may be true for a well-designed unit burning the right fuel in a large, ventilated room. But a seller’s page is not a measurement, and the conditions that cause incomplete combustion are exactly the ones a home cannot always control: a door closed on a cold night, a cheaper fuel, a burner run longer than usual.
The regulator does not tell you to trust the unit. It tells you to have a detector. That is the standard to follow.
How we wrote this page
We have not burned an ethanol fireplace or measured its emissions. This page is built from the Régie du bâtiment du Québec, the U.S. Consumer Product Safety Commission and reporting on Fraunhofer WKI’s laboratory tests, each named where it is used. We do not sell ethanol fireplaces, fuel or alarms. If you feel unwell while a fireplace is burning, treat it as a CO emergency first and a question second.
FAQ
Do ethanol fireplaces produce carbon monoxide?
They can. The Régie du bâtiment du Québec states that incomplete combustion in an ethanol fireplace can produce carbon monoxide and other harmful gases, and Fraunhofer WKI’s tests found CO among the gases ethanol stoves released.
Do I need a CO alarm if my ethanol fireplace is certified?
Yes. Certification shows the design met a standard such as UL 1370 or, in Quebec, ULC/ORD-C627.1-2008. It does not control your room size, ventilation or fuel. The RBQ calls a CO detector essential.
Can I smell carbon monoxide from an ethanol fireplace?
No. Carbon monoxide has no smell, which is why an alarm matters. The CPSC lists headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion as symptoms.
Does opening a window remove the need for a CO alarm?
No. Ventilation lowers the concentration of byproducts, and the RBQ requires a well-ventilated room, but it does not tell you when CO has built up. The alarm does that.
What should I do if the CO alarm goes off while the fire is lit?
The CPSC says to get outside to fresh air immediately, and then call 911. Leave the fire; do not stay to put it out.