I've posted several times on this subject, there's some good information in the thread links provided by Hung Muscle (tip o' the hat to you, sir!)

An additional consideration: besides the other stuff in the links above, one snort/dose of poppers causes an instant (within 5 or 10 seconds) average 50-point drop in systolic blood pressure, a 25 point drop in diastolic bp, and a 45 point (!) increase in heart rate. That's a pretty serious slam to your system, and that's how it is likely to kill you if taken in combination with some other drugs (or if you have any type of cardiovascular disease.)