Carbon Monoxide Safety: What Every Homeowner Should Know

The Silent Killer in Your Home

Carbon monoxide (CO) is called the silent killer for a reason. You can't see it, smell it, or taste it. But every year in the UK, around 60 people die from carbon monoxide poisoning, and a further 4,000 are treated in hospital. Many more cases go undiagnosed because the symptoms mimic common illnesses.

As Gas Safe registered engineers working across Portsmouth and Hampshire, we take carbon monoxide safety incredibly seriously. This isn't a topic where we crack jokes — it's genuinely life and death. Here's everything you need to know to keep your household safe.

What Is Carbon Monoxide?

Carbon monoxide is a poisonous gas produced when fuels — gas, oil, coal, wood — don't burn completely. When a gas appliance is working properly, it produces carbon dioxide (CO2), which is harmless in normal quantities. But when combustion is incomplete (due to a faulty appliance, blocked flue, or poor ventilation), it produces carbon monoxide instead.

CO enters your bloodstream through your lungs, preventing your blood from carrying oxygen. In high concentrations, it kills within minutes. At lower levels, it causes chronic symptoms easily mistaken for other conditions.

Symptoms of Carbon Monoxide Poisoning

CO poisoning symptoms are vague and flu-like, which is why many cases go undiagnosed:

• Headaches — Often described as a dull, persistent headache
• Dizziness and nausea
• Tiredness and confusion
• Shortness of breath
• Stomach pain
• Visual problems
• Collapse and loss of consciousness (at high levels)

Key warning signs: symptoms improve when you leave the house, multiple people feel ill at the same time, pets are affected, or symptoms worsen in winter when the heating runs.

What Causes Carbon Monoxide Leaks?

Most CO incidents in the home are caused by faulty, poorly installed, or badly maintained gas appliances:

• Faulty boilers — The most common source. A cracked heat exchanger, blocked flue, or poor combustion can all produce CO. Regular boiler servicing is your best defence.
• Blocked flues and chimneys — Birds' nests, debris, or damage can block the flue that carries exhaust gases safely outside. If the gases can't escape, they come back into your home.
• Poor ventilation — Gas appliances need air to burn fuel properly. Blocked air vents, sealed-up rooms, or new double glazing without trickle vents can starve appliances of oxygen.
• Faulty gas fires and cookers — Any gas appliance can produce CO if it's not burning correctly.
• Poorly installed appliances — Incorrect installation is a leading cause of CO incidents. Always use a Gas Safe registered engineer.

How to Protect Your Household

1. Install a Carbon Monoxide Alarm

This is the single most important thing you can do. A CO alarm costs as little as £15-25 and could save your life.

Where to place CO alarms:

• In every room with a gas appliance (boiler, fire, cooker)
• In bedrooms or nearby hallways
• At head height on a wall or on a shelf (CO mixes with air, unlike smoke which rises)
• NOT directly next to the appliance (at least 1-3 metres away)
• NOT in damp areas like bathrooms (unless it's rated for it)

CO alarms have a 5-7 year lifespan — check the expiry date and test monthly.

2. Get an Annual Gas Safety Check

Every gas appliance in your home should be checked annually by a Gas Safe registered engineer. This includes your boiler, gas fire, gas cooker, and any other gas appliance.

During a gas safety check, we'll:

• Check all gas appliances are burning correctly
• Inspect flues and ventilation
• Test for carbon monoxide emissions
• Check gas pressure and gas tightness
• Issue a gas safety certificate (CP12) for landlords

Landlords: You are legally required to have an annual gas safety check on every gas appliance in your rental property. Failure to comply can result in fines, prosecution, or imprisonment. We issue same-day certificates and cover all of Portsmouth, Havant, Waterlooville, and Chichester.

3. Never Block Ventilation

Gas appliances need air to burn safely. Never block air bricks, vents, or grilles in rooms with gas appliances. If you've had new windows fitted, make sure trickle vents are included and open.

4. Know the Warning Signs on Your Appliances

Your gas appliances give visual clues that something might be wrong:

• Yellow or orange flame instead of a crisp blue flame (on a gas hob or boiler pilot light)
• Black marks or staining around the appliance
• Excessive condensation on windows in the room
• The pilot light keeps going out
• A musty or unusual smell (not the gas itself, but the incomplete combustion products)

If you notice any of these signs, stop using the appliance and call a Gas Safe engineer.

5. Only Use Gas Safe Registered Engineers

For any gas work — installation, repair, or servicing — always use a Gas Safe registered engineer. It's the law. You can verify registration at gassaferegister.co.uk. At Blimp Plumbing, both Scott and Fraser are fully Gas Safe registered for work on boilers, central heating systems, gas fires, and all domestic gas appliances.

What About Boiler Servicing?

Annual boiler servicing is your front line of defence against CO. During a service, we'll strip down key components, check for cracks in the heat exchanger, test combustion readings, and verify the flue is clear and drawing correctly.

A service costs around £60 – £100 and takes less than an hour. Compare that to the potential consequences of a CO leak, and it's the best money you'll spend all year.

Carbon Monoxide Safety Checklist

Here's a quick checklist you can act on today:

• CO alarm installed in every room with a gas appliance? Check the batteries and expiry dates.
• Annual gas safety check booked or up to date?
• Boiler serviced within the last 12 months?
• Ventilation clear — all air vents, grilles, and trickle vents unblocked?
• Flames burning blue on your gas hob and boiler?
• No black marks or staining around gas appliances?
• Flue clear — nothing blocking the boiler flue outside?
• Family knows the symptoms and what to do in a CO emergency?

Book Your Gas Safety Check

Don't put it off. A gas safety check takes under an hour and gives you peace of mind that your home is safe. We cover Portsmouth, Fareham, Gosport, Havant, Waterlooville, and Chichester. Call or WhatsApp us to book.

Your boiler can't tell you it's producing carbon monoxide. But a Gas Safe engineer and a CO alarm can.