It is not all that simple. It depends on many factors:.
Colony size, number and size of boxes, type of lids -- insulation and under-lid clearances, -- entrance size (and number), and ambient temperatures day and night are just a few things that affect air circulation and air exchange with the outdoors.
Less is more if it does the job. Measure mites before and after.
This is art, and not so much, science.
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