Disposable hand warmers turn up the heat in your mittens by means of an exothermic reaction that, in essence, just creates rust. Each pouch typically contains iron powder, salt, water, an absorbent material, and activated carbon. ... It helps retain the moisture so that the reaction can occur.

How do HotHands hand warmers work?

As soon as you open a HotHands pack and remove the mesh bag, though, the specially formulated contents of the bag (which include iron powder, salt, and activated charcoal) are exposed to oxygen and react with it in a process called oxidation. This process is what makes HotHands warmers work.

Can HotHands hand warmers start a fire?

The fire was quickly put out and no one was hurt. ... Maples said the vehicle was experiencing issues with its exhaust system at the time of the fire and the excess heat caused a package of hand warmers to melt into the carpet, intensifying the fire.