How do Air Activated Warmers Work?
The air-activated warmers are self-explanatory. They work as soon as air hits them. The process is significantly more complicated than that. Every hand warmer comes sealed in a packet that contains a variety of substances: iron, cellulose or sawdust, water, vermiculite, activated carbon, and salt.
Once you unzip the packet, oxygen and air flows into the contents and begin oxidizing iron and turning it into rust. The salt speeds up the oxidization, and the carbon distributes the heat evenly. The only reason for the sawdust is the make the packet have content, so it takes up a little space
The actual process is an electrochemical process where the iron gives up electrons, and the oxygen gains electrons. This process on a microscopic level is what generates the heat. The final rusting process leaves the iron taking up more space than the iron occupied initially; in other words, the iron increased in size. When the process is over, the packets are unusable and need to put in the trash.
They work best when in confined spaces like pockets. However, the process can generate immense heat. It is best if you have a layer in between your skin and the hand warmer. Extra caution should be displayed with children.