That Ayoue 474++ de-soldering station that arrived today, well it didn't take long to 'take it apart' :-) Something I saw in a vid on YouTube suggested the exhaust air was just vented into the inside of the box - and there's not even a fan to vent the insides, nor even any holes that would allow natural air circulation through convection. So I made a cannister which I will fill with activated charcoal filter material (if it ever turns up in the post), machined from 3" diameter 10g alloy tube and fitted with turned caps for the ends. The bottom cap I left three milled tabs for hold down screws, matching holes were drilled and tapped into the bottom of the case. Hose connectors were turned from hex brass rod and a length of 3/8" silicone tube was used to connect the pump to the cannister, and again from there to outside the case. Not sure where in the case I'll vent to but likely I'll make use of the covered unused hole in the front face as that saves me drilling another. I haven't powered it up yet again but I'm hoping the cannister might also knock the edge off the noise too..
ChrisH