Hei! All this discussion about Carbon Dioxide in overwintering hives is all very interesting, even if some of the info is dubious science. It all started with the suggestion that some winter loss could be explained by suffocation -- I would suggest that nobody has actually claimed to have had such a loss, if they had it would be worth discussing why and how to avoid it. We use fairly well sealed hives here to overwinter (mid-Norway) with a ventilation opening at the bottom.The only loss mechanism we have big problems with is starvation. If the winter starts early and finishes late it can be diffucult to get the bees to feed properly at the end of the autumn and the late winter/early spring period can be very difficult. However, the point is nobody here has ever had an unexplainable winter loss as far as I know. Assuming they arent hermetically sealed in, that is we arent talking about way out abnormal hive arrangements ----can/ do bees suffocate over the winter? Cheers Tony --------------------------------------------------------------- Anthony N. Morgan (Tony) Fax: +47 73 89 62 86 "Stavshagen" E-mail: [log in to unmask] Midtsandan Sor-Trondelag College 7563 MALVIK Elec. Eng. Department Norway 7005 TRONDHEIM, Norway ----------------------------------------------------------------