I don't see how it could possibly be bad. It pretty much just changes the temperature of the air you breathe in. It's not like walking outside in the winter is going to be bad for your lungs over time. I'd be sick as hell by now if that were the case. I would say it would be better for your lungs then the hot air. Although, a bong hit usually isn't very hot anyways.

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Any law against what I do on this forum would be impeding on my right to freedom and the pursuit of happiness. So unfortunately, I'm forced to play the role of a cannabis grower instead of actually participate in the hobby. (All pictures are pulled from the internet and knowledge is only portrayed as personal experience without ever having any actual experience)