Steam 'em

Both heat and cold have been used to treat bedbug infestations, but research and data are still scarce. Many of the following concepts and theories are general rather than bedbug-specific, but can still be applied to bedbugs.

Heat treatment normally refers to structural heat treatment. Super heated air is released into the target area and circulated, and the temperature is raised to 140-160oF for several hours. This is to ensure that the temperatures in the harborages are maintained above the thermal death point, which is about 113oF. The biggest challenge is that, unless temperature can be raised up rapidly, bedbugs would try to escape the heat by moving into deep cracks or exiting the unit being treated. Therefore, the heated air needs to be well circulated to be able to penetrate into deep cracks, and the bedbugs have to be well contained either by caulking or insecticide dust. But I highly doubt that this step is currently being taken.

Relative humidity also plays an important role in structural heat treatment. Insects are able to lower body temperature by evaporative cooling, a mechanism that is similar to sweating. As water is released to the surface of the body and evaporates, heat energy - latent heat of evaporation is released along with it, hence the body cools down. However, if relative humidity is too high, less water will be vaporized, and hence less heat will be removed from the body. Therefore, in general, it is to our advantage to have high relative humidity during structural heat treatment. On the other hand, with low relative humidity, although an insect is able to effectively cool down its body by evaporative cooling, it loses water at a faster rate and will eventually die of desiccation. In this case, it is important to not keep any water nearby, otherwise the insect might still be able to survive.

I mentioned the use of boiling water and steam in my previous posts. The biggest advantage of using boiling water and steam is that they kill instantly on contact. (Previously I said that the temperature of boiling water was 100oC, twice as high as the thermal death point for bedbugs, 45oC. But this kind of comparison makes sense only when the Kelvin scale is used. Temperature expressed in Celsius or Fahrenheit is not a ratio variable since zero degree on these scales is not an absolute zero point. Nonetheless, the temperature of boiling water is much higher than the thermal death point for bedbugs, making it lethal enough to kill instantly on contact.)

While it is generally not practical to use boiling water to treat an entire infestation, it also has some advantages. There are quite a few items that can be dis-infested with boiling water:

Anything that can withstand high temperatures, such as cookware, bakeware, dishware, kitchen utensils, etc.

Steam can be practically used to treat most items. Steam is about 100oC at standard atmospheric pressure. But while it takes 1 calorie to increase the temperature of 1 gram of water by 1oC, it requires 539 calories for 1 gram of water at 100oC to convert to steam at the same temperature. Therefore, same amount of steam carries a lot more heat energy than same amount of boiling water does, even though the temperatures are the same, and this is the reason why steam burn is worse than boiling water burn. When steam hits a bedbug, phase transition occurs again, but in the opposite direction, namely condensation instead of vaporization, and the significant amount of heat energy is released to hit the bedbug. However, not all steam units are suited for bedbug treatment. You should choose a unit that produces steam of slow vapor flow (so that it would not blow away nymphs and eggs), low moisture and high temperature.

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STEAMERS. If bed bugs have a weakness, it's elevated temperature. Temperatures of about 120&degF are lethal to most insects provided they cannot escape to a cooler location. The advantage of steam is that heating is intense and immediate, killing both bugs and eggs on contact.

The types of steamers used for bed bug treatment are like those used for sanitizing floor drains. When targeting bed bugs though, the less moisture emitted the better, especially when treating mattresses and other slow-drying materials where mold growth is a possibility. Low-moisture steamers are available from such companies as AmeriVap Systems, Atlanta, Ga., 800/763-7687; and Hi-Tech Cleaning Systems, Columbus, Ohio, 866/606-1355. It is important to have a commercial-grade steamer with a water tank large enough to accommodate extended use between fill-ups. Most machines come with variable steam outputs and multiple attachments. Larger brush heads (like the triangular one pictured in the photo below right) usually work best. Small diameter tips are less efficient and frequently emit too much pressure, causing bugs and eggs to be blown off the substrate. While some of the dislodged bed bugs may die, others could survive and be scattered here and there.

When using steam, it is important that the bed bugs be exposed to lethal temperatures. Ideally the steamer head should be moved directly over the surface being treated. Holding the steam head farther away might only give the bugs a warm moist bath. A good way to confirm that lethal temperatures are being achieved is to use a digital infrared thermometer. Instantaneous temperature readings can be reached by pointing the device at the area just treated. Alternatively, one can hold their hand several inches from the steam head and slowly and carefully move it closer. Vapor too hot to touch is what's needed to kill bed bugs and eggs on contact. An effective way to further elevate the temperature of emitted vapor is to wrap the brush head of the steamer in a towel. A small tea towel works well and can be secured to the steam head using the spring-mounted clips (see photo on page 30). This technique produces vapor so hot that the steam head can now be moved quickly and efficaciously over infested and suspect areas. Using the towel method, lethal temperatures can be achieved several inches from the steam head, which can be useful when treating hard-to-reach areas (e.g., between cushions of upholstery or the framework of sofas and box springs). Towels that become overly moist can be replaced.

Steam can be used to treat almost any area where bed bugs are found or suspected. Logical places include beds, couches and recliners, baseboards and carpet edges, beneath and within nightstands and dressers and floor areas (especially under and around beds). Avoid treating finished wood surfaces or delicate items that might be damaged by high heat. Vacuums and especially steamers are useful when battling bed bugs. Neither, though, affords residual protection against bugs or eggs which may have been missed.

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