Here's a link to Doran darkroom louvres:

http://www.bhphotovideo.com/bnh/cont...ughType=search

Basically they are baffled vents that allow air to pass through, but not light. Useful for intakes on flowering cabinets where you need to prevent light from leaking in. Not super cheap, but they don't break down or wear out or anything.
jamstigator Reviewed by jamstigator on . JOURNAL OF A MADMAN Hello, Cannabis.com! I am happy to say that I have finally registered after months of reading all of your wonderful, insightful posts! I look forward to speaking with "youse" and sharing the herbal bond that brings us together! SO let's begin... ONCE UPON A TIME...I walked out my door to get the mail, and LO & BEHOLD, I stumble across a notebook with a CD in it. On the front of the notebook are the words: "Please post me on Cannabis.com." :confused: Now, being the kind-hearted and Rating: 5