I used to mess around with nitrous a lot when I was high. I thought it was a relatively safe drug. Just take extra vitamin b12 and youll be fine! Wrong.
After about a month of occasional nitrous huffing, i started to get intense pain in my lungs, usually about 5-6 hours after use. I would get like spasms where it was hard to breathe for a minute or so. Being a daily pot smoker, my lungs were already less than perfect. I had also been smoking about a pack of cigs a week. Now I know that the effects on the lungs of marijuana are questionable. Some say that a joint is as bad as a pack of cig's ( which is horribly untrue for me at least), but nitrous definitly causes pain every time I use it. It got to the point where i feared of getting lung cancer.
I have quit cigs and nitrous for the last few months, but occasionally i still get a lesser intense pain after a good joint. Whatever the case, i would say it's best to only use one drug that is inhaled/smoked. Stay Smart!