When conducting pesticide contact toxicity tests, its common to use C02 to  
put bees to sleep - just not too much, or its permanent.
 
Best I can tell, C02 has little/no longer term effects of the bees.   Some 
testing firms use Nitrous oxide to put bees asleep.  I don't like it,  
published papers indicate that it affects bee memory.  
 
Don't know if anyone has tested ammonium nitrate for sublethal  effects.
 
Jerry

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