CO2 as pest prevention?

My townhouse is built on a slab, and the coolant lines for the air conditioner run through a PVC pipe laid in that slab. On the outside end, the pipe is sealed up with a big, goopy mass of silicone caulking which looks like something a curious rodent could get through rather easily.

So, I was thinking to myself, what if I took a bucket, put a piece of dry ice in it, let it … well, not melt, but sublimate or whatever dry ice does. The CO[sub]2[/sub] would be heavier than air, so it would stay in the bucket. Assuming for a certain amount of error, I could, it seems to me pour this heavier-than-air gas into the open inside end of the pipe, effectively filling it with CO[sub]2[/sub] and creating a 20-foot-long tunnel of unbreatheable air for anything inside it.

Am I crazy, or would this kind of work? (I do realize that those aren’t mutually exclusive.)

You’re crazy.

If you are really concerned about rodent intrusion, put a piece of hardware cloth over the end of the pipe.

Interesting. I doubt there is much living down there beneficial to you except stuff eating what isn’t. Why bother with the bucket? Just slip the chunk of dry ice in the pipe. Yes, be careful to leave a vent. If I remember correctly, contained CO2 will product over 1000psi at room temperature.

CO2 and air don’t work like oil and water. They will slowly mix together, but may wipe out stuff first.

You might find a few more mosquitoes around. They seem to like c o 2.

I’ve had a similar idea - fix grubs, moths and other lawn pests by spreading plastic tarp over the grass, with dry ice scattered beneath it. I figure when you lift the tarp the next morning, whatever CO2 is left wafts away immediately, with no potential to harm pets - and the plants should like it. Not sure, tho…

Ha, if the CO2 doesn’t kill the rodents, the mosquitoes will beed them to death.

Bed bugs are attracted to it as well. You can look on YouTube to make yourself a homemade bed bug detector with dry ice

both this and thread starter’s suggestion are no more dangerous to pests than to a person who sleeps with his head covered by a blanket —or partying in packed pub everynight. in the case of the blanket, the sleeping person yawns or wakes up to realized the blanket is stiffling. in the case of the pub, one just steps out for a minute to gulp fresh air.

That isn’t true at all. Non life supporting heavy gases can build up in low areas and kill. Usually it is sewer gases, but many people have died in pits.

In truly closed areas such as the older submarines, they used lye to adsorb CO2 to prevent it from building up to lethal levels.

used to work in the mines. yes, in big and fully enclosed areas, a build-up of CO2 or CO can kill. nothing beats good ventilation. well, the coolant line is sure to have some airflow so CO2 is not likely to accumulate to deadly levels. in the case of the tarp, he’s not likely to tuck it in airtight since he’s doing it over grass and shrubs.

It might kill your lawn, since CO2 diffuses into wet surfaces and turns water into carbonic acid. You can experience this acid personally, by burping through your nose after drinking a carbonated beverage.