Heat rises, if the heating pad/lamp is at one end of the tote it will create a natural draft, any holes drilled low in the sides will help pull in fresh air at a lower level, but never had any issues myself using a large tote. I have noticed using cedar or pine shavings the tote tend to smell bad from waste shortly after changing ( a few days or so ) the new bedding I am using this time does not create that smell, it is a natural corn cob bedding and the chicks seem to like it better ( Becks Better Bedding ) amazingly when I recently changed it, it still doesnt smell and still looks clean, I like it myself that it doesnt smell bad, just smells like popcorn.Opening the top doesn't provide air movement at the level the chicks are at and CO2 would build up in the bottom of the tote. Drilling holes in the tote near the bottom would help move the air around just as it should be in a chicken coop. For the air to move up in a coop and pull ammonia fumes away from roosting hens you will also need ventilation at top and bottom