Heating Pads: Human Factors Traps for Designers and Users

Every year substantial amounts of property damage and numerous personal injuries result from failures of electric heating pads. This is a paradoxical situation considering that the intended product-function relates to the simple, safe, and reliable therapeutic application of heat to the human body. An investigation was conducted to determine whether traditional engineering criteria and human factors criteria were in conflict in the design of heating pads. The investigation revealed that the designers of heating pads have a tendency to overcome problems in hardware reliability by specifying how humans should behave relative to their product. Even heating pads that are Underwriters Laboratory (UL) listed contain user instructions which are unlikely to be followed under circumstances of normal use. The paper summarizes the functional design of heating pads, current instructions for their use, and applicable human factors considerations. An alternate approach to heating pad design is proposed which, if implemented, should prevent us from trading-in our heating pads for hot-water bottles. Beyond that, however, the paper serves as an example of how the application of human factors engineering principles can serve the goals of product safety and liability prevention.