15 Apr Killing bed bugs with heat – what temperature is optimum?

The bed bug’s achilles heel is heat. They can not live more than a few hours starting at 113F and as the temperature rises the time they live becomes shorter. At 122f all stages of bed bugs are dead within a minute.

A typical older model home dryer operates at 180f on hot, 160f on medium, and 140f on low. My own dryer in my garage was selected because it was quite old and it has an operating temperature of 190f on hot. All these temperatures are more than adequate to kill bed bugs. One must make sure, however, not to overload the dryer to ensure that all clothes reach at least 122f. Also, modern dryers focus less on heat and more on air movement for their drying action. I can not say for certain what each dryer uses for heat but it is pretty much safe to say that any dryer on the hot setting would be adequate.

A quick perusal of the internet suggests there is some debate about what the optimum temperature is for killing bed bugs in furniture with whole house or trailer based heaters. There are a number of factors involved in that question: input temperature, average temperature, time, heat loss, ability of objects to absorb heat, and potential cold spots.

The average temperature seems to receive the greatest amount of debate with a variety of temperatures between 130f and 160f being noted. Some argue 130f is the only safe temperature while others argue differently. In reality the more important number is the input temperature. If one is to heat a chamber to an average of 130f one must input much more than 130f to compensate for heat loss out of the structure (which depends on insulation levels and outside temperatures), heating the structure itself (which depends on the type of structure) , and the contents absorbing heat (which again depends on the amount and type of contents). Some whole house heaters using outside burners use an input temperature of 185f and hope to attain a return temperature of 150 – 155f average temperature. The folks using electric heaters are limited to 150f input temperatures due to CSA and UL limitations and can only obtain average temperatures in the 130f to 135f range. I suspect a fair bit of the debate about average temperature has to do with the electric heat contractors defending their inability to use higher temperatures and therefore criticizing the potential damage of higher heat approaches. In reality a high heat contractor could easily regulate the equipment to an average temperature of 130f but could cause immense damage anyways depending on where the hot inputs were aimed.

The high heat contractors can boast of their ability to work faster and more effectively but must take great care to aim their 185f inputs at areas that can withstand a great deal of heat. These hard to heat areas, such as concrete walls, receive extra heat and is much more effective than the low heat contractors for these settings. On the other hand the exact temperature of the areas beside the 185f input area receives varies tremendously and it is an art to use this tool without damaging windows, floors, and contents. I find any time an input over 170f is used the damage potential is very high so these contractors have to be smart. Personally I limit myself to a 165f input at the maximum in my trailer for that reason. For delicate items such as electronics I drop my input temperatures lower than 150f and rely on huge air flows and super insulated trailers to keep the average temperature within acceptable bed bug killing temperatures.  This way I can use more heat or less heat and more time or less time depending on the heat sensitivity of the items I am heating.

The electric heat contractors boast that they are less likely to cause damage but are much less effective in getting bugs out of dense objects. They will also aim their input temperatures at strategic spots, not so much to avoid damage, but to actually get killing temperatures to the middle of dense objects.

For example, I typically find that the core temperature of a mattress follows about 20f behind the average temperature in my trailer. Therefore if my average temperature is 140f my core temperature is 120f. That temperature, on paper, kills the bugs. I would not dream of taking that mattress in my home because there is no room for error. The safest method of allowing for error would be to allow more time for heating. But the closer the core temperature is to the average temperature the slower the temperature rise. It might take 5 hours to raise the core temperature an additional 5f which is expensive. The easier method of attaining a safety margin is to increase the temperature but this has additional damage risks.

The folks using 130f average temperatures, because of the 20f temperature differential between average and core temperatures, have to direct 150f inputs directly at hard to heat items because 130f will be inadequate by itself (130f minus 20f for heat transfer = 110f which will not kill bed bugs). This might be safer over all but is very slow and the risk for bugs surviving in a place where the 150f input was not directed is higher. Be very wary of the fast electric heat contractor.

All told using heat to kill bed bugs is an attempt to balance enough heat to kill the bugs with out damaging anything. It sounds simple but once you get into the nuts and bolts of making that happen it gets complicated.