Simple practical, non-toxic, non-flammable reaction for slow release of CO2

Someone I know (not me) has recently had problems with bed bugs. I have advised him his best bet is to (1) Buy a kick-ass steam cleaner and nuke the brutes from orbit, (2) get a professional pest controller in, and (3) Stop buying second hand furniture in future!

But being an inventive sort, he prefers a more subtle approach and is now intent on designing the perfect indoor bed bug trap.

It appears these critters are attracted by a localized $\ce{CO2}$ excess and by body heat, and are repelled by light and (presumably) excess heat. So assuming this trap won't involve a tethered goat or suchlike, he will need a compact, non-flammable, non-toxic, readily and cheaply available substance that can be persuaded to release a steady stream of $\ce{CO2}$ for several hours (without releasing CO or any other noxious or smelly biproduct).

I was thinking perhaps water dripping slowly onto calcium carbide, if there was some way of converting the resulting acetylene to $\ce{CO2}$ without burning it at a readily discernable rate. But a "slow burn", if it could be attained, might provide the heat source (although I reckon a more controllable electric heater would be better for that).

Any ideas? I suppose one obvious answer would be to simply buy a $\ce{CO2}$ cylinder, but could one then buy a sufficiently slow release valve to go with it?

• Hi and welcome to chemistry.stackexchange.com. Nice question! Feel free to take the tour. I am going to improve your question using MathJax in a few seconds. You can learn more about it in the help center. – Jan Oct 9 '15 at 12:40
• It is advisable not to conduct a CO2 producing reaction in a bedroom since it may most probably produce CO as well. And recently I heard a couple died by using a firewood heater in a closed bedroom – slhulk Oct 10 '15 at 3:56
• @slhulk This is oversimplified. It only applies to reactions where $\ce{CO2}$ is produced by oxidation. However, it is safe to say that no $\ce{CO}$ will be formed if the reaction is an acid-base reaction like the answers suggested below. – Jan Oct 10 '15 at 14:10
• Won't excess of CO2 be harmful as well?. – slhulk Oct 10 '15 at 16:57

I would recommend not touching or coming near calcium carbide at any rate. The acetylene it creates is explosive in certain concentrations (with a flame to ignite it) and notorious for extremely loud bangs. And it also is rather a diversion for what you want to do.

Instead, consider carbonates. Baking soda is one of the prime household sources of carbonates, and you just need to add an acid to release carbon dioxide; and nicely, the only by-product is water. You should use rather dilute acids so that you can slow down the reaction rate. Vinegar might not be the acid of choice (it has a distinct smell) but either essence of vinegar diluted or citric acid (which you should be able to buy from baking suppliers, too) should work. Or lemon juice.

To make the reaction sufficiently slow, you would need to (as I said) dilute the acid let it be poured into the baking soda solution slowly. Experiment a little! For a heat source, you could likely just put your average heating cushion underneath.

(Personally, though, I would use the steam cleaner because it sounds most kick-arse!)

An easy one is to mix together and then grind up citric acid with sodium bicarbonate (hydrogencarbonate). If you were making bath bombs, it's a similar method but without fragrances or colouring. You will literally need a few drops of water to help bind them and mould the solids, but that's it. When ready simply add water to the pellet/lump. Slow-ish $\ce{CO2}$ release.

Regarding bed-bugs, they are notoriously difficult to remove - I'd highly advise getting a pro involved as soon as possible.

For slow/steady carbon dioxide generation in a general sense, however, I'd go with yeast. East to find bakers yeast and flour in any supermarket. Google a basic bread recipe, and mix accordingly. If you do a slow rise, the dough will slowly release carbon dioxide (and other metabolic by-products) - depending on temperature, pH, and ratios used in the recipe, it could probably keep producing for 24 hours or more. And if you punch the dough down every so often, it may be able to keep generating longer than that. At the end, you can take your dough, throw in into a bread pan or just a sample tray, and make bread!

Pros:

1. No chemical safety issues