Ever wonder exactly what smelling salts, hartshorn or sal volatile are? Ladies of Regency England seemed to rely heavily on one of these items when in a swoon. OK, so maybe the lady in the swoon was not aware enough to worry one way or the other. However, those around her relied on one of these items to aid in reviving her.
All three of these items are, in fact, the same thing. Technically, the little bottle that was waved under the nose of the prostrate lady contained ammonium carbonate, which is a crystalline substance that releases ammonia gas. It is this gas that irritates the membranes in the nose, causing the muscles to commence breathing.
Sometimes this substance was from a distillation of hart (deer) horn shavings. It was called sal volatile by some because of its effectiveness and swiftness in reviving the prone.
All I can say to that being wafted right under my nose is...OUCH.