page_title: Hand warmer
section_title: Air activated (iron)
hierarchical_section_title: Hand warmer / Types / Air activated (iron)
caption_attribution_description: Hand warmer with scale
context_page_description: Hand warmers are small packets which are held in the hand and produce heat on demand to warm cold hands. They are commonly used in outdoor activities. Other types of warmers are available to provide soothing heat for muscular or joint aches.
  Depending on the type and the source of heat, hand warmers can last up to 10–13 hours.
context_section_description: Air-activated hand warmers contain cellulose, iron, activated carbon, vermiculite (which holds water) and salt and produce heat from the exothermic oxidation of iron when exposed to air. They typically emit heat for 1 to 10 hours, it usually takes 15-30 minutes to start to heat up, although the heat given off rapidly diminishes after 1–2 hours. The oxygen molecules in the air react with iron, forming rust. Salt is often added to catalyze the process.
caption: Crystallisation-type hand warmer with scale showing metal disc trigger
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