exuast question

so i just ordered a 150watt hps light and a 4 inch fan with carbon filter and was wondering if i could hook up the carbon filter to my lights air intake to my fan to exuast the hot air from my light and have the odor control at the same time. or do i need a second fan for light

If you get a high enough cfm fan you can do it all in one swoop... recommend at least a 300 cfm fan for that if not 500 cfm.

its a 170cfm fan with a 6x 12 carbon filter and a mini floru lux light with 2 4in flanges

Yup..I would go Passive Intake>>Carbon Filter>>Light>>Out of Grow Space.
With that small of a fan make sure you don't put alot of bends or long runs in your duct work as every 90 degree bend is like adding 4 ft of duct.

box is two 18 gallon totes rite now with a 3 gallon tote dwc setup . hopefully next gro is gonna be in a 20x28x4ft tall cabinet with dwc setup in one of the 18gal totes so i wont have to many bends or to long of a run its gonna be filter with like 1.5 foot to lite then 1.5ft- 2ft to the fan n then out of the box. might put two little cpu fans blowing air in