I think the housing you are on about is the pump.
No you shouldn't be able to get air through them, or very little.
Once you have the new maintenance station installed pour a little cleaning fluid into it and do a head clean.
You should see the fluid and ink coming through the pipes to the waste tank.
I have found the pipes from the pump block if not regurlary kept clean with a bit of cleaning fluid in the maintenance station and a head clean.
Sometimes the ink dries almost like pencil lead in these and can be very tricky to clean out.
Also I don't know about anyone else but I have removed the metal panel covering the ink lines in front of the maintenance station.
It seems a little pointless and is very handy to see the ink lines are clear of blockages.
SC