Bilge Blower

Yes, I have the 3 clam shells (just like Sylvester Stallone in Demolition Man)

I just wasnt sure if the fumes were forced out by sucking fresh air in.

My current blower hangs from the inside bottom of the top of the bilge area (I have a I/O). Is this ok if the fumes are at the bottom? Should I have a hose run from the blower to the bottom somewhere?