... oxygen in the air, it can give out heat. Non-woven fabrics bag's feature is high ... begin oxygenation, this process will continually give out heat for 10 to 12 hours at least. This process ... may take up 30 minutes to reach its therapeutic temperature, please on pain area.Warnings:1. Do not ... and for people not fully aware to the sensation of heat.3. People with diabetes, frostbite, scars, open wounds ...