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Hotties Thermal Packs Limited SAFETY UPDATE SUMMER 2008.
MICROWAVE THERMAL PACKS HAVE BEEN AROUND FOR 15 YEARS OR SO. They provide heat and the health benefits of heat without the fiddle of hotwater bottles or the hazard of handling boiling water to fill bottles.
Are they safe? Firstly we should say that conventional hot water bottles cause a significant number of serious scalds. In the last published HASS figures approx 1500 hot water bottle scalds were referred to A and E in the reporting year. Hot water bottles have been the subject of a number of product recalls for faulty stoppers or substandard construction.
What is microwaving? It is simply the application of heat by microwaves. These microwaves excite water molecules and heat things up. If you know how much water is present, you can calculate the time required for a microwave of given power to raise the temperature by a known value in degrees centigrade.
What happens if they are heated for too long? For some products, they just get hotter and hotter.
Gel and wax containing products can reach very high temperatures and may explode or combust. In 1999 after several serious incidents a woman was killed in the North East when her gel pack exploded and in effect napalmed her with hot sticky gel. Gel products have as a result been largely withdrawn from the UK market. Some gel cold packs can still be found which say they can also be heated in the microwave. This should never be done.
Many products have been introduced with wheat, seeds, peat, fruit stones, lavender and other natural products. These are natural products and vary in their water content. With use they dry out, even if a glass of water is placed in the microwave. When they dry out, the time to heat up in the same power microwave greatly reduces. If they overheat and reach a high temperature, they can start to cook and continue to heat up further even after they have been removed from the microwave. This heating can lead to spontaneous combustion. Earlier this year a woman was burnt to death when her lavender wheat bag set alight in her bed. The fire brigade reported that they had been called out to at least six serious house fires caused by igniting wheat bags. Great care must be taken with these products.
Hotties are different. They contain a fixed mass of water absorbed onto a nonwoven pad and sealed under vacuum in a specially engineered laminate pouch. This means that the rate of heat up is mathematically predictable. If the product is overheated it will expand and burst. Remember, steam fills 22.4 times the space of water. This prevents dangerous temperatures and pressures being reached and is a visual indicator that overheating has occurred. The nonwoven pad is capable of holding much more water than is put in the Hottie, so even after it has burst, the water does not rush out. Most of the water remains in the pouch. These safety features were built into Hotties from the beginning. That is why in 15 years and 2 million Hotties, nobody has been seriously scalded.
