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Has anyone successfully built and used a DIY heat chamber?

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  1. BeBu_throwaway

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    Posted 5 months ago
    Thu Apr 20 2017 14:59:53
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    I'm considering building a heat chamber out of 2" rigid foam insulation, as described in:

    Title: Economical, Localized Heat Treatment for Control of Bed Bugs infestations
    Authors: Roberto M. Pereira, Philip G. Koehler, Margie Pfiester and Wayne A. Walker
    Institution: University of Florida

    Details can be found here starting at page 61:
    http://ipm.ifas.ufl.edu/resources/grants_showcase/people_and_communities/bed_bugs_manual.pdf

    In essence, the box is constructed out of rigid insulation, sealed with duct tape or equivalent, heated with oil heaters, and employs electric fans to ensure the hot air reaches all points in the chamber. You also need to use remote thermometers and/or temp probes to make sure it gets hot enough for long enough. I've read enough about this to know the weakness point is the presence of "cool spots" which will prevent reaching 100% mortality.

    I'm interested in hearing from anyone who can provide advice on how to do this properly. Ideally, I'd like to rent/buy temperature probes and a data logger connected to my laptop, so I can be certain a lethal thermal dose is delivered throughout the chamber.

    Anyone interested in learning more can review the link above, and this thread with comments from users bed-bugscouk and P Bello:

    http://bedbugger.com/forum/topic/diy-heat-chamber-idea

    Any guidance is greatly appreciated.

    Thanks.

  2. BeBu_throwaway

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    Posted 4 months ago
    Fri Apr 28 2017 19:18:58
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    I also posted this to the DIY subreddit and received a surprisingly helpful response. The entire thread can be found HERE

    Here's what Reddit user InductorMan (an engineer) had to say:

    So I did this. I don't think I ended up having bed bugs, but we came back from vacation and only after returning did we realize that the bites we got in the last location were probably bed bug bites. So for good measure I sterilized all our belongings this way.

    In the course of that process I learned a couple of things. I'm an engineer so I'm wary of the non-idealities of any system, I think this made me well placed to detect pitfalls of that particular method. I read the paper by the way.

    The first thing I noticed was that putting bedding in a wad into the chamber, after hours of exposure to the 125-140F chamber air, the interior of the wad was at 85F. Bedding and all other wadded cloth are excellent insulators.

    It took approximately 24 hours for the heat to penetrate to the center of my duffel bag, and I periodically opened the chamber and stripped off layers of the packed goods that had reached the right temperature (as measured by my el cheapo IR thermometer).

    Next, this same duffel was resting on the ground for the first day. The underside of the duffel where it touched the rigid insulation never got hot. In the insulating competition between the duffel and the 1.5" rigid insulation, the duffel won handily. The insulation of the duffel made heat transfer so slow that it was never able to build up any temperature against the wall of the insulated box.

    My solution to this was to grab wooden planks and put them up on blocks of foam, to make a rack that the stuff went on. This allowed the air to circulate under the goods, and prevented any cool spots on the chamber insulation .

    So in total, the lessons were:

    -heat transfer through packed goods or closed in things takes for ever. The chamber will need to be at temperature for many, many hours before the interior of the goods are at temp.

    do not let anything touch the chamber walls, floor, or ceiling. It can create cold spots. This will require you to put things on some sort of rack. Although rigid insulation is a good insulator, your contaminated goods may be better insulators. You need to ensure that every side of all goods are bathed in hot, circulating air.

    Ultimately my system may never have seen the test of real live bed bugs, I guess we'll never know (well I hope we'll never know!). But I took great, some would say obsessive pains to probe the items with my thermocouple probe and IR thermometer; and the amount of effort it took to get all those temperature readings above 125F was shocking. So I think it's worth sharing the experience. You will need a good infrared thermometer (probably <$25 from your hardware store). And lots of diligence.

    *********

    InductorMan: thanks so much for responding. I have to say, getting an answer from a P Eng who has actually built this thing is hugely comforting and helpful. Your comments about keeping top/bottom/sides clear of material is really good intel.

    I hope you don't mind if I pepper you with some questions over the next day or two.

    What do you think of using remote sensors for monitoring temperature? What I have in mind are

    Wireless sensors on batteries that connect to an indoor digital reader (I have used these extensively to monitor kill temperatures to date: in my dryer, in my dishwasher (which gets even hotter than my dryer), and in my freezer; and,

    BBQ-type sensors, that are attached by wire to a digital reader.

    I reckon this might allow me to continually monitor temperatures at various locations without opening the chamber and letting hot air escape.

    Also, how did you physically assemble the insulation boards? Did you use some sort of wooden strapping to hold them together? And what did you use to seal the mating surfaces?

    Thanks in advance for any further feedback, greatly appreciated.

    ***********

    Not a licensed engineer, I'm an EE (PCB level electronic design and some mechanical design on the side). Just FYI!

    The thermocouple probe I used is exactly like a BBQ thermometer, it was extremely useful. The wireless probes sound good too! They sound excellent actually. At first I was freaking out about batteries + heat but then I remembered that I actually baked my GoPro + batteries after looking up the battery max exposure temp. So alkalines should be fine.

    The chamber I made was only about 1.5 x 2.5 x 8 (height x width x length). I also used an external heater in the form of a small fan driven space heater. This is probably inadvisable for the house-combusting reasons contemplated by the paper authors. Blocking the flow can of course cause fires. But I was pretty careful. What I did was make one hole for the heater on the end face of the box, and then on the lower corners of that end face and the opposite end face I made two little 4"x4" downwards-opening regulating flaps. The idea was to be able to either cause s net flow of air towards the far end of the box or send most of the air back to where it came from to help even out the temperature.

    The whole thing was just duct tape. I taped the insides first in flat pattern, folded it up, put some little pieces of tape on the folded-up seams on the outside while I finished taping the insides seams, then taped the outside seams. What was nice about this was that the outside seams didn't get hot, so the duct tape actually held well (hot duct tape will eventually just let go, at least when it's new). The top of the box was hinged (by only taping the outside along one edge) and then long duct-tape straps on the remaining sides hanging down from the top and duct tape patches below them on the box sides to protect the surface of the insulation served as buckles to keep the lid closed.

    Part of why this worked is that the heater, being outside of the box, kept the whole box under positive pressure. This meant that the non-ideal seams around the lid didn't matter, since ingress of cold air was prevented.

    The rigid insulation is... Rigid! When it's all taped up, it was strong enough for my box. An 8x8x8 box might be a bit floppier but I think a couple strategically placed wooden stringers could solve that. You could probably still use duct tape. If I were building a box of that size I'd probably just build it out of foam and tape only, and then add wood where needed.

    Also the temperature regulation was pretty easy (although dangerous, for the same reason it was easy). All one had to do was close up the vent flaps somewhat to increase the temperature. The vents were downwards opening so putting a heavy object (I used a drinking glass) under them would prop them up to whatever position you wanted. Putting them partially closed would choke the heater's air flow somewhat and increase the temperature. Obviously this is an intrinsically dangerous way to regulate a space heater, so I always probed the area in front of the heater outlet carefully with the thermocouple after each adjustment. I also found that the heater output varied by about 10 or 15 degrees over the face of the heater. I would typically target a range of 130-145. By the time the air was on its way out of the box it was at 125 or so, at least after the goods had reached temperature.

  3. hidingbugs

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    Posted 4 months ago
    Sat Apr 29 2017 3:06:49
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    Heres old thread about diy heat chambers

    http://bedbugger.com/forum/topic/diy-heat-chamber-idea


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