In case you are wondering, the red taps are for steam, the green tap is water and the blue tap is air. The internal width of this fumehood is 93 cm.
A retired Professor friend of mine reminds me that more effective anhydrous conditions can be achieved when the nitrogen/vacuum delivery inlet is instead placed at the top of the condenser. I will remember this for next time.
He also shares with me a design for the bubbler which makes it harder or near impossible to suck air back into the system. It is made up of two Dreschel bottles (like the one containing the CaCl2 in the above image) which are placed in series, with the first reversed. The second is almost filled with oil, which the nitrogen bubbles through. Any suck-back results in the oil in the second bottle sucking into the first, and only after almost the whole volume of oil has been transferred can air get in. Turning up the nitrogen transfers the oil back to the second bottle.