Heated blankets provide warmth through insulated wires woven into the fabric. Laying on a heated blanket is highly discouraged by manufacturers. This practice poses significant risks to personal safety and compromises the functional integrity of the heating device. The blanket is intended to serve as a top covering, allowing heat to dissipate naturally into the surrounding air and bedding. Compressing the blanket traps the heat, which can lead to localized temperature spikes and eventual product failure.
The Danger of Localized Overheating and Burns
Lying directly on a heated blanket prevents the natural dissipation of heat, forcing the thermal energy to concentrate in the area of contact. This compression rapidly increases the surface temperature beyond safe limits, resulting in thermal injuries to the skin and underlying tissues. A particular risk involves “low-temperature burns,” which occur from prolonged exposure to temperatures only slightly above body temperature, such as between 109°F and 124°F (43°C to 51°C). When a person lies on the blanket, the pressure can reduce blood flow to the skin, which is the body’s natural mechanism for dissipating heat. The combination of sustained pressure, reduced circulation, and trapped heat significantly lowers the temperature threshold at which a burn can occur.
Over time, chronic, low-level heat exposure can cause a mottled, reddish-brown skin discoloration known as erythema ab igne. This indicates sustained thermal injury to the skin. The lack of proper heat dissipation when the blanket is compressed bypasses the device’s built-in thermal safety mechanisms, which rely on the air to transfer excess heat away from the heating element.
Protecting the Blanket’s Internal Wiring and Controls
Lying on a heated blanket subjects the internal components to excessive mechanical stress and compression. Heated blankets contain insulated wires or carbon fiber elements that are designed to be flexible but not to withstand constant, heavy pressure. The continuous pressure can crush, kink, or sharply bend these internal heating wires. This damage creates an electrical fault, as the wires may fray or their insulation can fail, causing them to touch and create a short circuit. A kinked wire can also increase the electrical resistance at that specific point, leading to a hot spot where heat concentrates excessively.
These localized hot spots can melt the surrounding fabric, insulation, or even ignite a fire due to the thermal breakdown of the materials. The control unit and integrated thermostat sensors are also vulnerable to damage from direct pressure. If the control unit or its connection points are crushed, the safety mechanism can malfunction, causing the blanket to either fail completely or continue heating unchecked despite a thermal fault.
Specific Populations Requiring Extra Caution
Certain groups have a heightened risk of injury when using heated blankets, even as a top layer. Individuals with diabetes, especially those with peripheral neuropathy, have reduced sensation in their extremities, making them unable to sense when the blanket is too hot. Immobile individuals, such as the elderly or those with certain disabilities, are also at increased risk because they cannot easily adjust their position or remove themselves from a heat source. Infants and young children are particularly vulnerable because their bodies have a reduced ability to regulate core temperature, which can lead to overheating.
Pregnant individuals are often advised to use caution, as prolonged elevation of the core body temperature may pose a concern. Anyone who is incontinent should also avoid using heated blankets, as moisture can cause the electrical wiring to malfunction and create a shock hazard.
Recommended Safe Usage and Alternatives
A heated blanket should be placed on top of you, over the top sheet, as the final layer of bedding. It must always be laid flat, never folded, bunched, or tucked under the mattress, as this traps heat and damages the internal wiring. Use the blanket solely for pre-warming the bed and turn it off before falling asleep, unless the device has an automatic shut-off feature. A safer alternative explicitly designed to be lain upon is a heated mattress pad, sometimes called an electric underblanket.
These devices are constructed to be placed directly on the mattress, beneath the bottom sheet, and are engineered to handle the compression of a person lying on them. Heated mattress pads are considered safer because their design ensures the wires lie flat, minimizing the risk of kinking or bunching that can cause hot spots and electrical faults.