Smoke detectors.

Are there any smoke detector modules available anywhere. In most Indian sites I've seen only gas detectors but not any smoke detectors.

And by the way what is the best way to detect fire. Smoke, temperature or something else?

I wanna use PICAXE the fire alarm project because it is $)cheap $) and it is easier to program than PIC. Which version of PICAXE do you think I should use?

Thanks in advance.

Conventional smoke detectors for domestic and commercial alarms are readily available (in most countries) and use an alpha emitter (americium-241) as the detection method. The alpha particles ionise the oxygen and nitrogen molecules in the air of the detection chamber and set up a minute current flow. The smoke molecules neutralise the charged particles which alters the detection current so setting off the detector alarm.

There are many industrial forms of fire detection such as thermal sensors (resistance, bi metallic strip, fluid expansion bulbs, fluid fracture bulbs), infra-red detectors, ultra-violet detectors and no-doubt many others but it is best to detect early smoke, rather than wait until flames occur.