How bad is inhaling helium and nitrous oxide (not mixed, although that would be even more hilarious!) for your lungs?
Well, helium is almost completely unreactive, the only danger when inhaling helium from a balloon is not being able to get enough oxygen to breathe. IIRC You can OD on Nitogen Dioxide and out of the hands of a professional is pretty dangerous, but I imagine it wouldn’t cause any harm to your lungs.
The cold and high pressure direct from the bottle is dangerous. Although there is O in N2O, it is not enough to support life so a constant pure supply will eventually kill the user.
Now passing around the nitrous line for 10 or 15 minutes among enough people that one gets plenty of air between hits can be very interesting 
Balloon gas isn’t always pure helium though - sometimes it is something called ‘HeliHi’, which sounds like it might be a mixture of helium and hydrogen, but I’ve not been able to find that out for sure.
Certainly breathing hydrogen would be bad.
I have done the balloon gas thing several times and each time I woke the next day with a very sore throat that lasted several days; I’m not sure what the reason is for this, but I have often wondered if allowing the vocal cords to vibrate at a greater rate (and possibly a greater amplitude) than normal might injure them.
A very sore throat could be due to the other gasses and bad stuff in the industrial gas quality type gas. There is definitely a difference between medical grade nitrous and industrial n2o. The industrial n2o often has, among possible other things, a sulfur dioxide mask.
I don’t agree with that. From here - “Hydrogen is not toxic by any route. Asphyxia may result if the oxygen concentration is reduced to below 18% by displacement.”
Looks like you’re right there; I’m sure I had learned somehwere that hydrogen was toxic because it was so reactive, but it looks as if I was misinformed.
In any case, breathing or unneccesary handling of a mixture of gases that includes hydrogen and oxygen in would still be rather unwise (if the proportions are such that would support combustion)
So as long as you dont inhale nitrous straight from the tank (i’ve seen a balloon shatter whilst filling), its medical grade and you get enough air inbetween it should be OK? Also what would a combination of Nitrous and Helium be called? And is it legal to buy nitrous? I’ve seen it for sale in car part shops for nitrous kits but i’m not sure how safe that is for inhaling.
Well, that is a bit like saying there is O in CO2 but not enough to support life. Or are you talking about the mix in the bottle?
You can’t breathe N2O because the oxygen is already bound to the nitrogen. It is not really toxic, just suffocating. Nitrogen Dioxide is toxic however, so don’t breathe that.
I certainly can breath N2O, it is wonderfully intoxicating.
CO2 is good enough to extinguish a fire and it can certainly can suffocate a person - the O in N2O, while not flammable, will support combustion but not life. Yes, I’m talking about the gas in the bottle.
That’s not safe. IIRC, the manufacturers usu. add stuff specifically to make it unpleasant/unhealthy to inhale. Medical-grade tanks are obviously OK (if the mix of Oxygen is safe, naturally), though difficult to come by, I believe.
The easiest route is “whip-its”–though I would never advocate the intentional misuse/abuse of such a product–namely the nitrous chargers that are used in whip cream dispensers, commonly avail. at kitchen-supply stores.
Happened too long ago to find a link (early 80s), but my dentist’s assistant ODed on NO[sub]2[/sub] a day or two before my appointment. The dentist was a bit curt when I asked for nitrous during the visit; it wasn’t until a day or two later I found out why.
Doh! N[sub]2[/sub]O. Consider me slapped.
We generally allow threads about the physiological effects of controlled or regulated substances. We do not permit threads about the best ways of obtaining or using them. This thread seems to be veering in the wrong direction, so I’ll close it.
bibliophage
moderator GQ
UPDATE
neutron star was about to post the following quotation from http://www.medhelp.org/forums/addiction/archive/223.html when I closed the thread.