Oh yeah, I'm not saying it doesn't I just haven't heard of it. I would assume that exhaust leaks, or improperly positions exhaust exits would be the primary cause here. Perhaps a CO detector would be good for piece of mind?
Either way, frankly I'd prefer to avoid adding a cap anyway unless I have to. I like the idea of having it, and had one for a bit that I enjoyed, but I really like having the bed open. Is it a requirement that dogs in crates have the cap?
I really care about the dog obviously, and if it's gonna take a cap to make sure he's comfortable then I guess I'll make due. I'm just not sure if I want to commit to that fully, especially if I don't have to.