Frost-free: Frost-free freezers prevent ice buildup by automatically defrosting approximately once daily. A timer turns the compressor fan on and off, while simultaneously turning on a small heater to melt away any collected frost. During the defrost cycle, the internal freezer temperature does not change by more than two degrees, so food is not adversely affected. The slight temperature change concerns some consumers who have heard that their food will preserve better in a manual, rather than frost-free freezer. However, temperature changes in the frost-free cycle are approximately the same as the changes in a manual defrost freezer where the compressor cycles on-and-off. Frost-free freezers do not cause freezer burn, which occurs when food placed in the freezer is improperly wrapped or kept frozen for an extended period of time. Wrapping food in heavy-duty aluminum foil, plastic-coated freezer paper or polyethylene bags prevent freezer burn.