a small closet about the size of a hatch back car works fine. i mean my homie had this VW rabbit, and when we only had a lil bit of weed we would go pile into his car and just sit there and hot box, like when we only have .5 grams. but theres ben alot biggger hotboxes in that car. i mean we have smoked OZs hotboxing that shit with a steam roller about 1.5 feet long and 4 inches around. i mean towadrs the end of the OZ u couldnt clear the chamber cuz of all the smoke in the car.