What sensor or technique can I use to detect human presence in a place which is on fire?

  I want to build a system that detect people in a place on fire .... if this possible what can I use 
and how can I protect the circuit elements from fire 
thank you..

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As mentioned by previous posters:
- Infrared, look for a comparably cooler object, or a human-shaped hotter object in cooler rooms (my guess is not all rooms will be on fire). PIR/pyroelectric sensors should fall into this category as well, they are pretty popular for human motion detection. If you have a particularly good sensor, you could look for areas between 35°C and maybe 50°C (fire might heat up clothing, skin and such a bit) for a potential human.

- Audio sensor. If you can substract the audio noise of the fire somehow, you can try to find patterns for talking, screaming, yelling, and if your equipment and algorithms are really good, breathing and even heartbeats.

Futher possible ways:

- Radio waves (wireless internet). MIT has developed a way to identify moving people through walls using wireless signals. I am not sure if the random heat from a fire affects the radio waves though.

- Radar. Apparently there's some really sophisticated radar technology which can detect human presence, motion (sub-mm-accuracy) and a bunch more. You might eqip fire-resistand robots/drones with such a radar unit.

- Microwave sensors. Seem to work similar to the radar.

- Cellphone / mobile signals. Not really a sensor, but something to look for. Though not everyone always has his mobile phone with him, it might be an indicator to human presence. If you can locate cellphones, you might be able to find humans.

And here's a research paper on the subject called "A Survey of Human-Sensing: Methods for Detecting Presence, Count, Location, Track, and Identity".

You might want to look at methods firefighters and rescue workers currently use to find people buried under rubble after an earthquake, too.

As for the second part of your question:
Depends on the sensor, really. You might need active cooling, or you might just shove them into the equivalent of a thermos bottle (the vacuum between layers serves as a rather potent isolator).
The circuitry itself might be encased under the same materials fire-proof clothing is made out of (if you can survive it, electronics will probably as well), aforementioned thermos bottle-like concept, a fireproof box/case (there's a bunch of them) or other isolators.
It's hard to pinpoint a decent strategy as it's not clear how the technology is supposed to work. Does it need a readable screen, or other exposed elements? Can you just shove it into a closed box? Does the sensor type limit your choice in materials?. Really depends on the way you choose to go in terms of detection.

Just remembered another great insulation material: Aerogel.

There are some variants which are highly resistant to heat / fire with exceptional insulation capabilities. See this demonstration.

AliZ381 year ago

is there an possibility to detect human under mater in condition of disaster or if building is collapse if so what kind of sensor is required PIR senior or any other sensor can not detected human under material

iceng1 year ago

Audio filters to pass, to discriminate only the very low frequency of a heart pulsing sound and block ie to disregard all higher audio frequencies has been done with hotel rooms that had adequate sound proofing in walls and sometimes ceiling with floors.

As such a detector was picking heart sounds in adjacent rooms.

iceng iceng1 year ago

BTW fire makes high Fq noise, ergo the benefit of the low pass filter...

bwrussell1 year ago

It seems like IR would still be viable, just in reverse. Looking for cooler objects moving.

When talking about fire-proofing you're really talking about how long it can survive, how long it can be fire-resistant. Some sort of liquid cooling is a possibility but expensive and complex for a disposable device.