Stinkyattic's got it right! I think the vent-hole question is in regards to a light-baffle, something to prevent light from leaking into the ventilation hole.

A cheap solution is to install a PVC elbow joint (painted black) the same diameter as the hole, oriented so as not to let light in.

Whether you install a carbon-filter is up to you and how much the plants stink.

Good luck :thumbsup:
SmokeyD.Bear Reviewed by SmokeyD.Bear on . Garden Knowm Hey dude...its me again...just a few questions again... 1- is there such a thing as 2 much light? i now have 2 150watt CFLs..2 100 watt CFLs and 2 75 watt CFLs...in my new grow box..*patented by me...made by my barehands*...they are over my plants by about 1-2 inches...with 2 4" fans constantly blowing on them...with on nice fan blowing outward for my ventalation..which brings me to my next question... 2-what do i use to cover the hole in my box for the ventalation fan?...i figure that your Rating: 5