Preventing light leaks

My grow room has a small window and a door . The room next to it usually has some type of low light on. Do you guys recommend any material or fabric that will keep the room dark but will let air in and out of it ?

Fabric can harbor dust and particulate the could contain diseases. Whatever you put up you should make sure its a hard surface than can be cleaned easily. It should also be a glossy white on the inside to keep the light in your grow room and a darker color on the outside to block unwanted light. Be creative when it comes to these things. Something as simple as a plastic shower curtain will do the job depending on the space.

I used contractor garbage bags. Two tapped together cover a 5 x 8 window. From the outside all you see are blinds. Then Plastic behind them then curtains. Its nice too since it's my bedroom I can turn off the light and be in pitch black when ever I wan't.