Effect of temperature and humidity on heat effect of commercial chemical warmers based on iron powder

The effect of temperature and humidity on the heat effect of disposable warmers based on exothermic powder was investigated. A chemical analysis and microscopic observations were performed on exothermic powder consisting of iron powder, sodium chloride, vermiculite, diatomite and active carbon. The heat effect of warmers was investigated at temperatures of 15, 20, 25, 30 °C and humidities of 60, 70 and 80%. The microscopic observations revealed the morphology of the exothermic powder and the oxidation mechanism of the iron particles. The results indicate that temperature significantly affects the heat effect of the warmers investigated, whereas humidity has only a minor impact.