Stove fans are used to improve the circulation of heat which in turn reduces hot and cold spots throughout the home.

It doesn’t have any batteries so how does it work?

The stove fan is powered by the Peltier effect. This effect is due to a temperature difference by transferring heat between two electrical junctions.

The thermoelectric circuit is generated since it is composed of materials with different Seebeck coefficients. This is due to the junctions being made of doped* semiconductors.

In a Peltier fan the configuration is that of a  thermoelectric generator. 

*Doping is the intentional introduction of impurities to modulate electrical properties

Luckily, we didn't die in our beds

As I was surfing the web last night I casually asked my wife if she could smell burning plastic. She said she could and said she thought it might be coming from the bathroom. I looked in and light wisps of smoke were curling around the ceiling light, the source was a light switch. I warned her quickly and ran pell-mell down the stairs to alert the block warden and grab a fire extinguisher. When I returned there were flames that were starting to lick at the plastic ceiling. I had caught the fire just in time.

The good news is that we put it out quickly, nobody was hurt and no real damage was done but those powder fire extinguishers cause a dreadful mess and we were without power for a while. The most worrying thing is the ‘What if?’ questions – what if it had caught fire at 4:00am?