 There is a substantial fire risk if flammable materials such as clothing or bedding are left near a heater, especially synthetic fabrics such as polyester, which can melt or burn.Even though the surface temperature of the heater in normal operation is quite low, the extra thermal resistance of the clothing on the heater can cause its surface temperature to rise to the material's autoignition temperature.Some oil heaters contain strong warnings to avoid operation in damp areas (such as bathrooms or laundry rooms) because the moisture and humidity can damage components of the heater itself.