Your on the right track Diaperload. A blow off tube attaches to your carboy or bucket and leads to another container holding star san or another sanitizer. This allows air to bubble out and no microbes to come in. This is necessary when there is blow off (i.e. Krausen) coming out of the fermenter. You want a blow off because a airlock will get clogged and will cause a mess.
Every fermentation is different so do not stress to much about this one being more vigorous than your other ones.
Here are two pics from my fermentation fridge a while back so you get an idea how to do it. Keep in mind there are much many ways of doing this.
You can see the tube coming out of my actively fermenting beers, leading to a container of star san.
This one is a 1 gallon size batch that has a blow off to a 22oz bottle of star san.
Hope this helped!