Do Gas Heaters Produce Carbon Monoxide?
Published on : April 10th, 2025
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When the cold weather hits, gas heaters are a go-to for keeping our homes warm, comfortable and cosy. But while they’re convenient and efficient, there’s an important safety concern you shouldn’t ignore – carbon monoxide.
You might’ve heard of it before: it’s that invisible, odourless gas that can be incredibly dangerous if it builds up indoors. So, the big question is – do gas heaters actually produce carbon monoxide?
The short answer is yes, they can. But don’t worry, that doesn’t mean you have to ditch your gas heater. With the right knowledge and a few safety steps, you can enjoy the warmth without the worry.
In this blog, we’ll break down how carbon monoxide is produced, what signs to look out for, and how to keep your household safe while staying warm.
What is Carbon Monoxide and Why Is It Dangerous?
Carbon monoxide (CO) is a gas you can’t see, smell or taste – and that’s what makes it so dangerous. It’s produced when fuels like natural gas, wood, petrol or coal don’t burn completely.
In the case of gas heaters – from gas log fires to gas ducted systems – this can happen if the heater is faulty, poorly maintained, or used in an enclosed space without proper ventilation.
The real danger lies in how easily CO can build up without anyone noticing. When inhaled, it replaces the oxygen in your bloodstream, which means your body and brain don’t get the oxygen they need.
Symptoms of carbon monoxide poisoning can include headaches, dizziness, nausea, confusion and, in severe cases, unconsciousness or even death.That’s why it’s often called the “silent killer”. Being aware of the risks – and how to avoid them – can make all the difference when it comes to keeping your home and family safe.
How Gas Heaters Can Produce Carbon Monoxide
Gas heaters are designed to burn fuel efficiently, but when something goes wrong, they can start producing carbon monoxide. Here’s how that can happen:
- Incomplete combustion – If a gas heater doesn’t burn fuel properly, it can release carbon monoxide instead of just heat and water vapour. This often happens when there’s not enough oxygen for the fuel to burn cleanly.
- Faulty or damaged parts – Cracked heat exchangers, blocked burners, or other internal faults can disrupt normal combustion and lead to CO production.
- Lack of ventilation – Unflued gas heaters used in small or poorly ventilated rooms can quickly cause CO to build up.
- Poor installation – A heater that hasn’t been installed by a licensed gas fitter may not comply with safety standards, increasing the risk.
- Neglected maintenance – Dirt, dust, and wear over time can affect how your heater runs, turning a safe appliance into a hazard.
Regular servicing and proper use can help prevent all of these issues.
Warning Signs Your Gas Heater Might Be Producing CO
While carbon monoxide is invisible and odourless, there are still some warning signs that could indicate your gas heater isn’t running safely.
Keep an eye out for the following:
- Yellow or orange flames – A properly working gas heater should produce a steady blue flame. Yellow or flickering flames can mean incomplete combustion.
- Soot or scorch marks – Black marks around the heater, on nearby walls, or on the appliance itself are red flags.
- Pilot light going out – If the pilot light keeps going out for no clear reason, it could signal a deeper issue.
- Burning smell or stuffy air – Unusual smells or a feeling of stuffiness in the room could mean poor ventilation.
- Physical symptoms – Headaches, nausea, dizziness or shortness of breath while the heater is running may indicate CO exposure.
If you notice any of these signs, stop using the heater and get it inspected by a professional immediately.
How to Prevent Carbon Monoxide Buildup
The good news is that carbon monoxide buildup from gas heaters is preventable with a few smart steps. First and foremost, always have your gas heater serviced by a licensed gas fitter at least once every two years – or annually if it’s older. Regular maintenance ensures your heater is running efficiently and safely.
Ventilation is also key. Make sure the room you’re heating is well-ventilated, especially when using unflued heaters. Never block vents or airways, and avoid using outdoor gas appliances indoors – they’re not designed for enclosed spaces and can quickly lead to CO buildup.
Installing a carbon monoxide detector is another simple but powerful safety measure. These detectors can alert you to rising CO levels long before symptoms appear.
Lastly, trust your instincts – if something doesn’t seem right with your heater, turn it off and get it checked. A little caution goes a long way in keeping your home safe and warm.
Safety Tips for Using a Gas Heater at Home
Using a gas heater at home can be perfectly safe – as long as you follow a few simple precautions. Here are some handy safety tips to keep your household warm and protected:
- Get regular servicing – Have your gas heater checked by a licensed gas fitter every one to two years to ensure it’s working properly.
- Install a carbon monoxide detector – These devices can alert you to rising CO levels before it becomes dangerous.
- Use the right heater for the space – Avoid using unflued gas heaters in small or poorly ventilated rooms like bedrooms or bathrooms.
- Keep vents and airways clear – Good airflow is essential for safe combustion. Don’t block vents or cover your heater.
- Don’t use outdoor gas appliances inside – BBQs, camping heaters, and similar gear aren’t designed for indoor use and can be deadly.
A little extra caution goes a long way in keeping your home safe and cosy.
What to Do If You Suspect CO Poisoning
If you think carbon monoxide might be present in your home, act fast – don’t wait for symptoms to get worse. First, turn off your gas heater immediately.
Open all doors and windows to let in fresh air and help disperse any carbon monoxide in the room. If you or anyone else starts feeling unwell – think headaches, dizziness, nausea or confusion – leave the house right away and seek medical attention.
Next, call emergency services (000). It’s important to get professional help, even if symptoms seem mild. Once everyone is safe, contact a licensed gas fitter to inspect your heater and the rest of your gas appliances. Don’t use the heater again until it’s been checked and declared safe.
Remember, carbon monoxide is sneaky, but being prepared and knowing how to respond can make all the difference. Quick action can protect your health – and possibly save a life.
Stay Warm and Stay Safe
While gas heaters can produce carbon monoxide, following safety guidelines can significantly reduce the risk.
Regular maintenance, proper installation and ensuring adequate ventilation are all key steps in preventing CO buildup. Installing a carbon monoxide detector is another simple but effective way to protect your home and family.
Always be aware of the warning signs of CO poisoning, such as unusual flames, a burning smell, or physical symptoms like headaches and dizziness. If you suspect your gas heater is producing carbon monoxide, don’t hesitate to turn it off and seek help from a licensed professional.
By staying informed and taking necessary precautions, you can enjoy the warmth of your gas heater without compromising safety. Stay warm, stay safe.
Please note: This information is provided for advice purposes only. Regulations differ from state to state, so please consult your local authorities or an industry professional before proceeding with any work. See our Terms & Conditions here.
Do you have any questions about heaters producing CO? Keep reading for the answers
FAQs about gas heaters leaking Carbon Monoxide
Yes, all gas heaters have the potential to produce carbon monoxide, especially if they’re not working properly. This includes both flued and unflued models. The risk increases if the heater is old, hasn’t been serviced regularly, or is used in a space without enough ventilation. That’s why regular maintenance and safe usage are so important.
Since carbon monoxide is invisible and odourless, the best way to detect it is with a carbon monoxide detector. However, there are some signs to look out for – yellow or flickering flames, soot marks, pilot light issues, and symptoms like dizziness or nausea while the heater is running. If in doubt, turn it off and call a professional.
Unflued gas heaters can be used indoors, but only in well-ventilated areas and never in bedrooms or small, enclosed spaces. They release combustion gases directly into the room, so proper airflow is crucial. Always follow the manufacturer’s instructions and consider using a flued model or electric heater for safer long-term use.
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