How safe are poppers/Amyl?

I've never used Poppers or Amyl, how safe are they? Which brands are the best and which ones should you avoid? People seem to like Jungle Juice and Iron Horse brands. What exactly do they do besides making it easier to do receptive anal sex? Are they dangerous? Can you die or pass out from them? Is it like huffing a solvent? I'm in the USA and I know that the poppers here don't have Amyl in them like they apparently did in the 70s and 80s. BTW I put this in the GLBT section since I don't know ANY straight people who have ever used poppers at all and I've met lots of gay and bisexual men who have.