Hotboxing is really bad for your health

I love to hotbox because it gets you really high. But just recently i realized that if bong hits arent cleared than the smoke becomes stale after like 4 seconds. But what about being in a room full of obng smoke for 10 minutes. It HAS to be really bad inhaling all that stale smoke dont you think? so my question is, how long should i hotbox for before the smoke becomes too unhealthy