Older boilers can run safely for many years, but only if the combustion process is healthy and the system can vent exhaust gases correctly. Understanding the essentials of boiler carbon monoxide safety helps protect your household from an otherwise invisible risk.
Quick checks you can do now
- Ensure at least one working CO alarm is fitted and not past its expiry date.
- Check that vents, grilles and flues are clear of debris or obstructions.
- Look for staining, soot marks or unusual smells around the boiler casing.
- Make sure the boiler flame (if visible) is steady and blue.
Why boiler carbon monoxide safety matters
Carbon monoxide (CO) is produced when fuel does not burn completely. Older boilers are more prone to this if they have poor air intake, blocked flues or deteriorated components. Homes in areas with mature housing stock, such as Bordon, Whitehill and Liphook, often contain older appliances that benefit from regular safety checks.
CO is odourless and invisible, so prevention and monitoring are vital. A correctly serviced boiler should produce minimal CO and move it safely outdoors via the flue system.
Correct placement of CO detectors
A CO detector is one of the simplest and most effective safety measures. Placement matters because CO mixes with air differently from smoke. To maximise protection:
- Install a detector 1–3 metres from the boiler, ideally at breathing height.
- Avoid placing the alarm directly above the boiler or beside vents where false readings could occur.
- Fit an additional alarm near bedrooms so it will wake occupants.
- Check expiry dates; most alarms last 5–10 years.
Many homes across Alton, Farnham and the wider GU34 and GU9 areas still have detectors placed too high, too low or too close to the appliance itself. A quick reposition can make a meaningful difference.
Safe venting and flue performance
Your boiler’s flue system removes combustion products from your home, and any obstruction can allow gases to build up indoors. With older properties in GU35 and surrounding regions, flues may run through lofts, extensions or external walls that have been modified over time.
- Ensure flue terminals are not blocked by ivy, cobwebs or stored items.
- Check for corrosion, especially on older metal flues.
- Look for signs of water staining or condensation around joints.
- Confirm that loft flues have clear access for inspection.
If you have a room-sealed boiler, the flue must remain airtight so the boiler can draw fresh air in safely and expel exhaust gases without mixing them.
What a proper combustion check involves
A qualified Gas Safe engineer uses a flue gas analyser to measure combustion quality. This test evaluates CO levels, CO/CO₂ ratio and burner performance. Older boilers may drift out of specification over time due to worn seals, partial blockages or deteriorated burners.
A typical combustion check includes:
- Inspection of burner seals and casing integrity.
- Measurement of CO and combustion ratios.
- Verification that the flue pulls exhaust gases correctly.
- Assessment of ventilation routes and air supply.
If issues are found, they are often straightforward to rectify through cleaning, adjustment or part replacement.
Signs your boiler may need attention
While only proper testing can confirm safety, certain symptoms should prompt a professional inspection:
- Yellow, orange or flickering flame (on open-flued appliances).
- Condensation on windows near the boiler.
- Soot deposits around the flue or boiler casing.
- Frequent boiler lockouts or unusual smells when the boiler runs.
Reducing CO risk in older properties
Many homes in and around Bordon, Whitehill and Alton have boilers installed more than a decade ago. Although age alone is not dangerous, older systems benefit from closer monitoring. Consider the following homeowner checklist:
- Book an annual service with a Gas Safe engineer.
- Replace expired CO alarms promptly.
- Keep vents clear, especially in utility rooms or converted garages.
- Ensure loft access is not blocked so the flue can be inspected.
- Call for help if you ever feel unwell when the heating is running.
These small actions maintain safe combustion and reduce long-term risk.
Final thoughts on keeping your home protected
Reliable combustion, clear ventilation and correctly placed CO detectors form the foundation of safe heating, especially in older homes. A well-maintained system not only protects your family but also extends the life of the boiler.
For professional checks or support with older boiler safety, contact us at (01420) 558993.