My cabinet is set up like:

intake -> cooltube -> fan -> exhaust -> carbon filter

In other words, sucking air through the tube, and blowing it through the filter. But you can arrange it other ways. Probably just as common is:

intake -> carbon filter -> cooltube -> fan -> exhaust

You could move the fan to the other side of the cooltube/reflector and it'd work just as well; never had a problem blowing air or sucking air through a cooltube, either way works fine from what I can tell.
jamstigator Reviewed by jamstigator on . air cooled reflector I have an air cooled 600 watt hps lamp do i suck the air out of the lamp or do i blow air onto the light. Rating: 5