A blowoff tube is used during fermentation to allow excessive krausen to be expelled from the fermenter. It is used in place of a traditional airlock, particularly during times when vigorous fermentation is producing significant krausen which would clog a typical airlock, potentially blowing the top off the fermenter. This is typically a tube attached to top of the fermenter, the other end of which is submerged in liquid (preferably sanitizer solution). Blowoff tubes should be of sufficient inside diameter to avoid clogging. Typical 5/16" ID siphon tubing can be used, and typically fits into ports designed for airlocks, but it does have a tendency to clog sometimes, thus a larger diameter is preferable.