Hazard [Health Devices Jun 1989;18(6):234-5]

Problem

A member hospital reported that a blanket warmed in a microwave oven burst into flames when it was passed into a hyperbaric oxygen chamber. The hospital suspects that the blanket was smoldering within its folds when it was placed in the chamber. Our tests have confirmed that this is a likely scenario. We know of at least one other case where a blanket ignited while being heated in a microwave oven.

Discussion

A blanket inside the oven may warm because of absorption of microwaves by the blanket material, but the effect is likely to vary, depending on, for example, the material type and moisture content. However, microwave use may result in severe hot spots in the blanket and ignition due, in part, to uneven heating patterns within the oven. Unlike items heated within a conventional oven or warming cabinet, items heated in microwave ovens do not equilibrate to a set chamber temperature. Rather, they continue to heat as long as they are exposed to the microwave energy. Hot spots from microwave heating can cause smoldering and burning of the blanket while it is in the oven. Once removed from the oven, a blanket that is smoldering within its folds may burst into flames if exposed to oxygen or if permitted to smolder long enough.

1. Do not use microwave ovens for warming any blankets. Such use can result in fire, which could cause injury or death.
2. Use commercially available hospital blanket warming cabinets. Such cabinets are warmed by either electric heaters or steam and do not present a blanket ignition hazard, even if the warmed blanket is subsequently exposed to an open oxygen source or placed in a hyperbaric oxygen chamber.

• Blankets [10-415]
• Cabinets, Warming [10-540]
• Warmers, Blanket [10-414]

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