Help with air exhaust

I have a 3footlong, 2 foot high by 1.5foot in depth rectangular box for growing, I currently have 1 17'' Fluro tube and plan on installing another after seedlings.
I have a intake whole at the bottom with a reflect 1inch under to keep light in/allow air to get in.

Question - I currently have a 12V PC fan running in there just for circulation. I was wondering with the other light am I going to need to make it an exhaust fan to keep it cool. Will an exhaust help with quantity/quality/increase grow speed?

Yes you need an exhaust fan for air circulation and keeping the temps down and your plants need fresh air and there will be some stinking coming week2 or 3 or flowering until they are dried after flowering

You will need something to catch and filter that with your exhaust fan

Good luck

any ideas of how to put a carbon or charcoal filter on the exhaust?

look in the FAQ under DIY. Theres plenty of stuff there and you can use it for everything