A friend of mine sprayed "Black Flag Home Defense" insecticide under her computer. It died immediately. I'm trying to figure out why, and how fixable it might be.

I found an MSDS, but it only says what the active ingredient is, deltamethrin, 0.02%. Apparently everything else is proprietary and/or non-hazardous.

Deltamethrin is not water-soluble, so I'm thinking that this probably doesn't contain any water; more like nonpolar hydrocarbon sorts of compounds. I'm thinking there's some particular nonpolar solvent that makes up the bulk of it.

So, my questions:

  1. Information or informed speculation as to the likely solvent involved.

  2. For those with knowledge of electronics, information or informed speculation about the effect of such solvents on PC boards and electronic components.

Answers to 1 alone are also useful, as I can then ask on electronics.se what those compounds would do.

UPDATE: I don't have access to the computer myself. I passed on some of the suggestions to my friend, and she will bring it in to a shop and see how repairable the damage seems to be. Thanks for all your thoughts.

UPDATE 2: I spoke with the tech who looked at it. Apparently the computer was very dirty inside; years of dust, cigarette smoke residue, and insects. She's not sure exactly what happened, but there seems to be a short somewhere on the motherboard, and that may have fried the power supply as well. Given the dirt, it was probably not in good shape even before the incident; the heat sinks were thoroughly clogged.

Overall conclusion: keep your computer clean! Keeping unknown chemicals away from it is a good idea too.

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    $\begingroup$ Two questions which might help: 1. How much did she spray? From one quick spray to a full can. 2. Do the label or MSDS mention the aerosol used? $\endgroup$
    – Molx
    Commented Mar 31, 2015 at 3:37
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    $\begingroup$ When you say computer died, could you elaborate a little more? Does it power up at all? Any lights internally or externally? Do you see anything on the screen? I realize those are not chemistry type questions, but they would help with fixability. $\endgroup$ Commented Mar 31, 2015 at 4:54
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    $\begingroup$ Can you open up the computer case? Could it be that the insect driven by the insecticide enters the computer and causes a short circuit? $\endgroup$
    – SYK
    Commented Mar 31, 2015 at 8:04

3 Answers 3



So we could probably guess what's in the insecticide based on what's used in some of their other products.

Black Flag Flying Insect Killer

Tetramethrin - Sounds like the "active ingredient" here. By "active ingredient", I mean poison.

D-phenothrin - Another poison. This product sounds like it kills more than one insect.

Petroleum Distilates - Likely a solvent. Unspecified

Liquefied Petroleum Gas - Propane or butane. An aerosol propellant. Was your product from a bucket or can? If a can, then it probably has this stuff.

So what happened?

My guess is that one of the products created a short circuit

A short circuit is an abnormal connection between two nodes of an electric circuit intended to be at different voltages. This results in an excessive electric current limited only by the Thévenin equivalent resistance of the rest of the network and potentially causes circuit damage, overheating, fire or explosion.

Typically, when something like a computer experiences a short circuit, it will stop functioning, "die", once the irreversible damage is done. As specified in the above text, circuit damage is likely done, and the circuits will need to be rewired. If there was no damage, then removing any remaining substances through a solvent, followed by thoroughly drying the computer, would remove the short circuit and allow it to function normally. It's possible that if the short circuit was created by a solvent, that the solvent has already been removed by evaporation, due to common organic solvents' melting points.

  • $\begingroup$ Nobody comes here to get guesses! $\endgroup$
    – Georg
    Commented Apr 1, 2015 at 14:43
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    $\begingroup$ Given that the product is proprietary, and I'm not about to do a separation and NMR of the mixture, it's difficult to specify exact contents of the insecticide. Same with knowing exactly what happened given the amount of information OP has provided. $\endgroup$
    – John Snow
    Commented Apr 1, 2015 at 16:29
  • $\begingroup$ @JohnSnow: This seems like the best answer so far. However, I don't see how a non-polar solvent or alkane could cause a short circuit. Would such compounds conduct electricity well? It seems unlikely. $\endgroup$
    – Tom Zych
    Commented Apr 5, 2015 at 16:52

The only reason for a short could be that by spraying a lot of that can some moisture from air condensed due to the refrigerating action of the spray. But: Does the computer start again after some time has passed now? Usually all supply voltages in Computers are short-Proof and shut down on a short. After dryinfg the computer should start again.

  • $\begingroup$ An interesting point that had not occurred to me. But the computer still didn't start half a day later, so there's probably other damage as well. $\endgroup$
    – Tom Zych
    Commented Apr 1, 2015 at 15:14
  • $\begingroup$ Did You switch off mains (or pull the plug) if there is no real mains switch? $\endgroup$
    – Georg
    Commented Apr 1, 2015 at 15:17

From the answer of John Snow I saw that it contained Petroleum Distilates

From my years as IT tech it was absolutely forbidden to use any Petrolium/oil based product for cleaning out the computer parts, because they cause corrosion/react with the compounds.

The acidity of crude oil based products is just too high. It's also a damn good rust remover(try it, it makes your bike all sparkly new again). Even when refined it's still highly reactive(cleaning petrol, lamp oil, etc...)

So spraying it in your computer where there are heaps of soft, easely corrodable metals is generally a bad idea.

For your reading enjoyment

How to fix it? Depends, if pieces have melted I have bad hopes for you being to fix it. You might try dousing it in IsoPropyl Alcohol to flush away any solvents, but i'm afraid the damage has been done and the chips and resistors are dead.

You might be able to replace resistors if they are damaged. You can recognise those by them bulging out instead of having a flat top. Damaged chips are recognisable by being burnt. Might need a magnifying glass to see it.

But usually in these cases the damage is nigh invisible.

  • $\begingroup$ Because the problem was described as immediately failure, I'd put my money on a short over instant corrosion (although in any case, as you say, cleaning it is important to at minimum prevent further damage). Petroleum jelly, at least, is actually great at preventing corrosion on electronics, but can corrode certain insulators over time, like the insulation of some types of wiring. And oil in general makes a great insulator for example. $\endgroup$
    – Jason C
    Commented Mar 31, 2015 at 7:55
  • $\begingroup$ Petroleum based products are highly reactive. Just put some oil on a cloth and wipe it over some rusted metal. it comes off almost instantly. It will cause a reaction within a second, and if you have a nice hot computer with hot components to stimulate reaction, it's not entirely unfeasable. Just look at the chemical reactions in these gifs iflscience.com/10-chemical-reaction-gifs-will-amaze-you now these are pretty huge objects and they react instantly. Now imagine a small hot metallic wire reacting to a corrosive substance. its nigh instant reaction. $\endgroup$ Commented Mar 31, 2015 at 7:59
  • $\begingroup$ You're speaking of petroleum based solvents (like, e.g. gasoline) rather than petroleum based products in general (some of which are solvents, others of which are not only safe to use on electronics but widely used as insulators). But I admit to nit picking and losing sight of your point. Sorry. Distillates, like naptha or whatever, could definitely do some damage. $\endgroup$
    – Jason C
    Commented Mar 31, 2015 at 8:11
  • $\begingroup$ Crude oil "based" products are not necessarily acidic nor do they remove rust. They are excellent removers of dirt, but not of iron oxides. $\endgroup$
    – Curt F.
    Commented Mar 31, 2015 at 12:08
  • $\begingroup$ Such petroleum distillates are not acidic or corrosive at all! $\endgroup$
    – Georg
    Commented Apr 1, 2015 at 14:45

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