Thanks for your reply. I've been using the Provap since late spring of this year. I recently noticed some mite issues and realized I wasn't getting the same level of mite control as I was with a standard vaporizer for the past three years. I had been treating from the bottom of the hive (as I do with my standard vaporizer) but noticed a lot of leaking of OAV fog even I was using the insert that covers the screened bottom board. Maybe the OAV wasn't getting distributed throughout the brood nest. I also wasn't getting much mite drop. I'll try your method of treating from the top. Are you verifying the mite drops or doing alcohol or powered sugar mite counts?
I'll also second your comment about keeping the Provap outlet tube clean and wearing goggles. I also had an issue where the tube became clogged and the lid popped off as well.