Carbon Monoxide Safety: Symptoms, Causes & Prevention | Dawsons Fuels

There are many joys of an open fire or stove — warmth, comfort, and that relaxing glow on a winter evening. But any fuel-burning appliance (wood, smokeless fuel, coal, pellets, gas or oil) can produce carbon monoxide (CO) if it isn’t burning or venting properly.

Carbon monoxide is especially dangerous because you can’t see it, smell it, or taste it. The good news is that simple steps — servicing, chimney/flue maintenance, ventilation and fitting a certified CO alarm — dramatically reduce the risk.

Carbon Monoxide (CO): at a glance

What it is: a poisonous gas created when fuels burn incompletely.
Common symptoms: headache, dizziness, nausea, tiredness, confusion and breathlessness (often “flu-like”, usually without a fever).
Clue it might be CO: symptoms improve outdoors and return indoors, especially when heating is on.
Best protection: regular servicing + swept chimney/flue + good ventilation + a certified CO alarm.

What is carbon monoxide (CO)?

Carbon monoxide is a gas produced when carbon-based fuels (such as wood, smokeless fuel, coal, pellets, gas or oil) do not burn fully. If CO builds up indoors, it can make you seriously unwell very quickly.

What is carbon monoxide poisoning?

Carbon monoxide poisoning happens when you breathe in CO and it enters your bloodstream. CO binds to haemoglobin (the part of your blood that carries oxygen), which means less oxygen is transported around your body. That reduction in oxygen is what causes the symptoms — and why severe exposure can be life-threatening.

What causes carbon monoxide to build up?

In a well-maintained, correctly installed appliance with a clear chimney/flue and the right ventilation, fumes should vent safely outside. Problems usually arise when one or more of the following apply:

Blocked or restricted chimney/flue (soot build-up, birds’ nests, debris, damaged liners)
Poor ventilation (airbricks blocked, vents closed, sealed rooms without adequate air supply)
Faulty, poorly installed or poorly maintained appliance
Back-draughts caused by competing airflow (kitchen/bathroom extractor fans, tumble dryers)

Carbon monoxide poisoning symptoms (CO symptoms)

CO symptoms can be subtle at first and are commonly mistaken for a cold or flu (often without a temperature). Look out for:

Headache
Dizziness or light-headedness
Feeling sick (nausea) or being sick
Weakness or unusual tiredness
Confusion or difficulty concentrating
Shortness of breath
Chest pain (particularly concerning if you have heart problems)

Higher exposure can cause loss of coordination, collapse, loss of consciousness and can be fatal.

How to tell if it might be carbon monoxide

CO is more likely if:

Symptoms improve when you go outside and return when you’re back indoors
Symptoms worsen when the heating or fire is on
More than one person in the home feels unwell at the same time
Pets seem unusually lethargic or unwell

If you suspect CO, don’t “wait and see”.

What to do if you suspect carbon monoxide (do this now)

Open doors and windows to ventilate.
Move everyone into fresh air immediately.
If anyone has severe symptoms (collapse, serious breathlessness, sudden confusion): call 999 (or 112).
If you suspect a gas appliance issue or you’re unsure: call the National Gas Emergency Service on 0800 111 999 (24/7).
Stop using the appliance/fire and do not re-enter the affected area until it’s been checked and confirmed safe by a qualified professional.

If you feel unwell or are worried about possible exposure, seek medical advice. In an emergency, always call 999/112.

How to prevent carbon monoxide poisoning

1) Service fuel-burning appliances regularly

Have boilers, burners, stoves and fires serviced by a qualified engineer. This applies to all fuel types — including wood, smokeless fuel, coal, pellets, gas and oil.

For a broader seasonal safety routine, you may also find this useful: Get Ready for Winter: Your Ultimate Fireplace and Fuel Checklist.

2) Keep chimneys and flues clear (sweeping matters)

A professional chimney sweep helps prevent blockages and improves safe airflow. Guidance varies by appliance and usage, but typical sweeping recommendations include:

Smokeless fuel: at least once per year
Coal: twice per year
Wood-burning fires/stoves: quarterly when in use (or at least twice yearly for regular users)

If you burn a mix of fuels, follow the schedule for the one that needs sweeping most often.

3) Don’t block ventilation

Good airflow is essential — even in winter:

Keep airbricks and vents clear
Use trickle vents on windows
Avoid sealing rooms with fuel-burning appliances unless you’re sure the air supply meets the appliance requirements

4) Use the right, dry fuel

Wet wood can cause sluggish fires, extra smoke and soot build-up in the flue, increasing maintenance needs and contributing to poor draw. For best performance, use Ready to Burn kiln-dried logs and store them in a dry, ventilated space.

Learn what “Ready to Burn” means here: What is the Woodsure Ready to Burn Scheme?

Shop our fuels: Kiln-Dried Logs & Heat Logs | Smokeless Fuels | Biomass Wood Pellets

Carbon monoxide alarms (monitors): what to buy and where to fit them

A carbon monoxide alarm is a simple, affordable extra layer of protection. It can alert you before you notice symptoms, including during sleep.

What to look for

Choose an alarm that conforms to BS EN 50291 (often shown on the unit/packaging).
Buy from a reputable retailer and follow the manufacturer’s instructions.
Test the alarm regularly and replace it in line with the manufacturer’s guidance.

Where to install

Fit alarms in rooms with fuel-burning appliances and near sleeping areas.
Follow the manufacturer’s placement guidance (height and distance can vary by model and situation).

Important: a CO alarm is not a substitute for servicing, sweeping and ventilation — it’s a back-up, not the primary control.

Myths vs facts

Myth: “I’ll smell it if there’s a problem.”
Fact: Carbon monoxide has no smell — you won’t detect it without an alarm.
Myth: “My appliance is new, so it can’t be CO.”
Fact: Installation issues, ventilation changes, or a blocked flue can create risk at any age.
Myth: “A smoke alarm covers CO too.”
Fact: Smoke alarms detect smoke, not carbon monoxide — you need a dedicated CO alarm.

Carbon monoxide safety checklist

Appliances serviced on schedule by a qualified engineer
Chimney/flue swept and inspected at the right frequency
Air vents and airbricks clear (no deliberate blocking)
Correct fuel used and stored properly (dry, ventilated)
CO alarms installed, tested regularly and replaced as recommended
Everyone at home knows: fresh air + ventilate + call for help

FAQs

Can carbon monoxide poisoning feel like flu?

Yes. Many people report flu-like symptoms without a fever, such as headache, dizziness, nausea and fatigue.

Can I smell carbon monoxide?

No. Carbon monoxide is colourless and odourless — you can’t detect it by smell.

What should I do if my CO alarm goes off?

Ventilate, get everyone into fresh air, stop using the appliance, and seek help immediately. If anyone is very unwell, call 999/112. If you suspect a gas issue, call 0800 111 999.

Do I need a CO alarm if I burn logs, smokeless fuel or pellets?

Yes. Any appliance that burns carbon-based fuel can produce CO if something goes wrong.

How can I light smokeless fuel more reliably (and avoid a sluggish start)?

Smokeless fuel generally prefers air from below. Follow this guide: How to Light Smokeless Fuel: A Guide to a Roaring Fire.

Need advice on safer burning at home?

If you’d like help choosing the right fuel for your appliance — from kiln-dried logs to smokeless fuels — speak to the Dawsons Fuels team or stock up online:

Firelighters & Fireside Accessories | Kiln-Dried Logs & Heat Logs | Smokeless Fuels

Last updated: 30 December 2025. This article is general safety information and does not replace professional or medical advice. In an emergency, always call 999/112.

Helpful external links:
NHS: Carbon monoxide poisoning
National Gas Emergency Service (0800 111 999)

The Down Low on Carbon Monoxide (CO): Symptoms, Causes and Prevention