Its a drug called Amyl Nitrate commonly used on the streets and in clubs. It comes in a small glass bottle. It is commonly inhaled through the nose. The effects are almost immediate, within 30-40 seconds, but last only a few minutes... the blood pressure becomes reduced followed face flushes and persperation.

Side effects are-
-confusion
-vomiting
-fainting
-nausea

In worst cases people have sniffed too much causing death.