Sealed heating system? You still need a carbon-monoxide alarm

Following the recent tragic deaths of two students in Northern Ireland where carbon monoxide poisoning was suspected, we came across this interesting and possibly life-saving snippet – it seems that homeowners and landlords where a sealed system or combi-boiler is fitted to their property, haven’t been installing a carbon monoxide alarm, believing their system to not require one.

The confusion comes from the name ‘sealed-system’ where the system is sealed against the interior of the house/room. This has led homeowners etc to believe they don’t need an alarm. However, it is possible for seals to fail and flues to become blocked causing the odourless, colourless and deadly gas to escape into the interior of a room, with potentially fatal consequences. “Sealed system” usually refers to a sealed  (unvented)  water circuit.  If the combustion chamber is sealed from the room, it’s called a “room-sealed” system.  Nearly all modern domestic gas boilers are room-sealed. The advice is to always fit a carbon monoxide alarm.

Room-sealed boilers draw fresh air for combustion from outside and use an electric fan, instead of a chimney, to provide the necessary draught through the combustion chamber.  This allows the flue pipework to be longer, and so makes installation more flexible.  The plentiful supply of oxygen due to the fan means that the gas burns completely leaving water vapour and carbon dioxide, not carbon monoxide.

Older room-sealed boilers always had the fan fitted on the exhaust side, blowing the combustion products away.  This meant that the air pressure inside the combustion chamber was always lower than the pressure in the room; in the event of the combustion chamber seal failing, air would always leak from the room into the boiler.

“the advice is always fit a carbon monoxide alarm”

Such installations are intrinsically safe; even if incomplete combustion is occurring and carbon monoxide is being produced, it can never be released into the room.

Modern, high-efficiency room-sealed boilers often have the fan fitted on the intake side, drawing fresh air into the combustion chamber.  This means that the air pressure inside the combustion chamber is higher than the pressure in the room; and in the event of the combustion chamber seal failing, combustion products can potentially leak from the boiler into the room.

It’s easy not to think about this when replacing an older boiler with a brand new one — whose seals will be perfect, and whose fan will be running at full speed.

But seals and bearings can deteriorate over time.

“failed seals”

If the fan is running at less than full speed, there may not be sufficient oxygen for complete combustion, leading to carbon monoxide production; and this can then leak into the room through failed seals.

A carbon monoxide alarm is about the same size as a normal smoke alarm. Like a smoke alarm, they usually sound an audible alarm when set off and feature a ‘test’ button for you to make sure the battery isn’t dead and the alarm is working properly.

They’re not expensive – you can easily pick one up from shops like Argos for around £15. Some incorporate a normal smoke alarm, others a visible warning light. Why not buy a pack and install one for an elderly relative? They’re much less likely to have windows open etc meaning the gas can build up to lethal levels much quicker.

“staying in holiday accommodation?”

Smaller ‘patch’ alerts are also available. The patch in the centre of the card turns a different colour if carbon monoxide is detected. They’re ideal if you’re staying in holiday accommodation and just want that little extra piece of mind.

Remember, carbon monoxide can’t be smelt or seen by humans and by the time you’re aware something is wrong, it may already be to late.

The Fire Service reckon on average, 50 people a year are killed by carbon monoxide poisoning due to faulty heating appliances. A very sad figure indeed.

The Fire Service also point out that detectors should comply with British Standard BS 7860 and that they are warning devices only. You should not rely on them entirely, nor use them as a substitute for properly maintaining and regularly servicing your heating system.

More information on carbon monoxide poisoning, alarms and safety advice can be found on the Fire Services website – click here

photo credit: victory

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