That's exactly what they do, just vent. However, if you wind up rolling the sled they will also puke out oil and, some of the "stuff" that comes out of the hose is in the form of gooey white crap! Its just moisture/oil combo but it does make a mess under your hood. I put a longer piece of hose on mine and run it below the oil tank and onto a rag that is zap strapped to the hose. Just make sure that the hose does not get clogged/plugged or you'll pop a engine cover gasket, I know! Also, FYI, Alpine in Salmon Arm sells a "anti-spill rollover tank" that works like a hot damn! If you do rollover this small tank collects the spilt oil before it pukes outta the hose and, when you upright the machine it pours the oil back into the oil tank. I know that this works very well too! Sherm