I never had the problem of them regaining consciousness.They died almost instantly.
Iddee, Please let me add a bit more to my post and description of the technique.
Between the gassing and the fanning, it is not more than a minute or so. The CO2 is simply used to knock them off of their comb and prevent them from flying off. The plastic enclosure prevents them from flying off before or during the gassing and ensures sufficient CO2 concentration to be effective, even if it is windy.
This technique might best be used where you only have one shot at the cut out maybe due to distance or construction timeline, might not have a vacuum (a forest), or where a vacuum might be ineffective (hive up inside a wall or tree that you cannot cut into, or possibly not even be able to see into).
And as for your rats had you applied mouth to mouth resuscitation
just as soon as they went to their knees, I suspect you could have saved most of them. That is essentially what the fanning does it applies the equivalent of mouth to mouth without getting too personal with the ladies.