What Are The Types Of Hand Warmers?
When it comes to hand warmers, there are two types of chemical reactions used to generate heat: supersaturated solution and air-activated. These chemical reactions work to produce an exothermic release of heat, but do so through very different methods. These types of warmers are best implemented when placed in tight spaces, such as in a glove, shoe or pocket. They offer a lightweight and portable approach to generating heat to help keep the extremities warm during cold weather.
How Air Activated Hand Warmers Work
The first type of hand warmer often used is the air-activated hand warmer. These generate heat through a process known as oxidation. Once the package seal that they are purchased in is broken, the air that makes its way into the pack enters through the tiny perforated holes in the warming bag itself. The air molecules react with the iron in the hand warmer bag and form iron oxide, otherwise known as rust. The bag is designed to trap any moisture, keeping the user's hands dry, while an ingredient called vermiculite holds the heat in and prevents it from leaving the site of the reaction. Conversely, to disperse this heat throughout the pack material, carbon is often added as well. Salt is often included for its catalyzing properties in producing instant heat. To fill the remaining space in the bag, cellulose is often used as an inert ingredient, along with charcoal and sometimes sawdust.
How Supersaturated Solution Hand Warmers Work
The second type of hand warmers use a chemical reaction called a supersaturated solution. These generally contain metal discs in the middle of them. In order to activate heat, the metal disc must be snapped. This causes the crystals within the warmer to precipitate. This released heat energy is held within the bag, compounding the heat to reach temperatures as high as 130 degrees Fahrenheit. These use table salt otherwise known as sodium acetate. An initial boiling of the hand warmer must be done in order to best dissolve the salt, thus creating a supersaturated solution capable of holding heat for extended periods of time. These pads are reusable, and can be boiled multiple times.
