Smoke/Heat Detection

Smoke detectors. We need them and we know that they save lives but when to use which?

Well, let's just say you live in a four storey, three bedroom house with a bedroom attic, cellar.

We'll start with the cellar. Every floor needs fire detection and the cellar, no matter how dark and damp it might be is no exception. An OPTICAL Smoke detector would be fine here as they are designed to detect larger smoke particles in the air. If the cellar has a couple of rooms and a stairway, it needs to be positioned somewhere it will be central so as best to cover both rooms.

On the ground floor you have the kitchen. That of course is where you do your cooking (and occasionally, burning too) so it's essential to have some protection in there but it's not a smoke detector you want at all as you'd be setting it off every time you burnt the toast. It's a HEAT Detector that's required. They are only triggered by heat and not smoke so you can burn as much toast as you like (I don't know what your hobbies are) and it's not going to trigger the detector.

You'd need a detector to cover the living room too but it doesn't have to be inside the room where you'll be looking at it, it can be just outside in the hall. The rule of thumb is that a detector covers the rooms that are within a 3 metre radius of it. As long as it's not too near the kitchen, where a heat detector might once again be better, an OPTICAL smoke detector would be the right choice.

Up to the first floor, say it's two bedrooms and a bathroom, you would place it on the landing, central-ish to the three rooms so that it covers them all. Often this places it right outside the bathroom which means an OPTICAL smoke detector would be unsuitable as they can be triggered by the steam from a bath or shower so you would put an IONISATION smoke detector there.

It's common to see someone has put the wrong smoke detector here because people don't always know the difference (and the two types of detector do look identical, to be fair) and because the OPTICAL smoke detectors are usually at least £5 cheaper.

Lastly the attic bedroom would also require detection and an OPTICAL smoke detector would be fine here.

Ideally (that's to say in a new build home or if a home is getting a complete rewire) all the detectors need to be mains powered with a battery back up and have a communication link between them so that if just one of the detector heads is triggered, they all sound the alarm.

Smoke detectors, Boothtown
27th of May, 2021

I was asked to look at two smoke detectors in this house. One was below a bathroom that had had a seal problem on the bath and the other was upstairs, outside that bathroom. Both had been going off for different reasons and the lounge one would not stop.

The lounge smoke detector had taken in water from the bathroom upstairs and was, in a word, knackered. So That was a straight replacement.

The one upstairs was going off because it was the wrong type of smoke detector for that location.

If an OPTICAL smoke detector is outside a poorly ventilated bathroom, it can be triggered by the steam from a bath which is what we had here. So it was again just a straight swap for an IONISATION smoke detector. Fortunately, this brand Aico is a brand i always use and the bases are identical, meaning swapping the heads couldn't be easier.