DIY Smoke monitor

I'd like a smoke alarm that turns the power off to the devices that are smoking.

Isn't that called a fuse?

Easy enough to arrange. Some of the more upmarket smoke alarms are available with a relay base (eg

I used to run an old minicomputer at home, 20 years ago. I built a circuit to do exactly this. It used an interconnectable smoke detector, from which I sensed the voltage on the interconnect terminals, and tripped off the mains supply. It also tripped off the mains supply if the room got too hot or there was mains interruption of more than half a cycle.

The smoke detectors I currently have at home run off my alarm/ home automation system. They are standard PP3 battery types, but the battery is replaced by a battery-sized module which runs from the 12V alarm supply, and provides a relay output which operates when the smoke detector draws enough current to operate its internal siren. It would be easy to use something like this, but I haven't seen the battery-sized modules for about 10 years now, and they probably don't conform to today's regs. In my system, in addition to alarm sirens, a smoke detector triggering also causes the central heating, aircon and ventilation fans to be switched off, and a number of lights to be switched on.

You can buy smoke detectors with relay bases in all sorts of configurations, operating from 12V, 24V, and mains, but they're much more expensive.

It happens that Matty F formulated :

..and this gadget has absolutely no relevance to that. It just shows you how thick the smoke is coming from your chimney or flue and optionally triggers an alarm to warn you if it goes beyond pre-set limit. As already said, only of use for those burning other than gas as a fuel, where smoke might be a problem.