Bed bugs are very sensitive to heat and are rapidly killed when exposed to temperatures over 45oC. If heat is used for bed bug control it is important that the high temperatures are applied suddenly; a gradual rise in temperature will cause the bed bugs to disperse, thereby potentially spreading an infestation. Thus using heaters to heat up a room to a lethal point for bed bugs is inappropriate.
The most practical method of exploiting heat is through the use of steam. The great advantage is that it will kill all bed bug stages including the eggs (most insecticides are non-ovicidal).
A study from the United States (Meek 2003) has shown that using a combination of steam and insecticides provides better long-term control than by using insecticides alone. As steam is composed only of heated water, some clients favour this treatment over chemicals, particularly for their mattress and bed. In fact at least one company in the United States will only use steam for controlling bed bugs on mattresses due to fears of litigation in case a guest has an adverse reaction to the insecticides.
It is important to note that there any many different brands and types of steam machines on the market, however not all are appropriate; the unit must be able to produce steam of a low vapour flow and high temperature. Steam flow rate must be kept to a minimum to avoid blowing bed bugs about and to reduce wetting. Like any tool, steam machines are only as effective as the operator. To achieve anywhere near eradication, an intimate knowledge of the pest and its ecology are essential, inspections must be diligent and the treatment process must be meticulous. The instructions of the steam machine must be read thoroughly noting all safety instructions prior to use. As all steam machines take time to reach operating temperatures, this can be done while the inspection is in progress.
- As the steam machines are operated with a low vapour flow rate it is necessary to place the nozzle directly onto the surface being treated; the temperature drops away rapidly from the nozzle and a separation of only a few centimeters will not be lethal to the bugs. The nozzle should be moved along at a rate of only 30cm per every 10-15 seconds.
- The steam treatment should start with the mattress and be applied to the seams, under labels and handles, and both inside and out of an ensemble base.
- It will be necessary to remove the material base of the ensemble, which should be kept, and if required, re-stapled after the infestation has been eradicated.
- Cushions of chairs and sofas should be treated next, paying particular attention to seams and buttons.
- Always check if the sofa is a sofa bed, and if so, treat the mattress as above. Carpet edges can also be treated with steam, along with the straight edge both above and below.
It is often promulgated that bed bugs can be killed via heat by placing infested materials into black plastic bags and then into the sun. However, this has never been fully scientifically investigated and is probably not effective with large items, which have a high thermal inertia. Thus this method is not recommended.