How Mycoal Warm Packs work.

When iron rusts it gives off warmth called oxidising heat, but you cannot feel this heat because its oxidising rate is too slow.  If this is speeded up, more heat is produced. This is the principle behind MYCOAL WARM PACKS.

The warmers are activated by removing them from their protective airtight packaging to expose them to air. The blended ingredients of iron, salt and water, combined with the oxygen from the air, causes the rapid oxidisation of the iron particles. This reaction produces heat.  The heating temperature and duration are controlled by the amount of air ventilation, which passes through the many tiny holes on the inner packets. The duration of the reaction is finite and the warmer should be disposed of after it has cooled.