Like you, I just hope I’m using the gas vap right. How long do you leave it in the hive for? I think 30sec is supposed to be enough but I probably left it going for well over a minute just to be sure...presume there’s no down side to leaving it going for longer but not sure?
My colony is brood and a half...I just used one scoop of the OA but wonder if a bit more should be used if the bees are in a bigger space...
The answer to how long is a simple one ... work out how long it takes to sublimate entirely the amount of OA you intend using (needs a bit of experimentation and a stopwatch). The time it needs to be in there is sufficient time for the amount of OA to fully sublimate.
This will, obviously, vary depending on the amount of OA you use and the heat you allow to be produced by the blowtorch you have selected. Once you have these parameters firmly established - as long as they remain constant whilst vaping - you will know how long you need the Gasvap to be in place.
I think the scoop on the gasvap is a bit on the small side if you are using Apibioxal (because of the additives in it) - with generic OA the scoop gives about 1.5gm of OA with a level scoop (again - that also depends on the granularity of the OA - you really need to weigh the amount measured by the scoop of your OA and once you have established that weight you are going to keep it constant - be it one scoop, two scoops or 1.5 scoops).
Once you have established how much you are going to use, it's a good idea to have some small test tubes or containers and weigh out your OA in advance and then all you have to do is tip the pre-measured amount in to the pan. Saves a lot of time and uses less gas in the torch.
So the answer, as it often is in beekeeping, is - it's your decision, it needs a bit of judgement and when you have found something that works - stick with it.
Leavinng the gasvap in place longer than necessary is not going to do any particular harm but it does mean that the device is going to be hotter than it needs to be for longer. Taking it away too soon risks having sublimate still issuing from the Gasvap which you don't really want.