Bizarre but apparently true. (http://www.newscientist.com/article.ns?id=dn7294)

The really interesting thing is that 80 ppm hydrogen sulfide is way, way, way, above the threshold of olfactory detection - which is about 2 parts per billion. So this is an incredibly stinky experience they are talking about.

Hydrogen sulfide is much more lethal than hydrogen cyanide - but the lethal level of hydrogen sulfide is something like 600 ppm. One of the things that is really bad about hydrogen sulfide is that it shuts down the olfactory nerve at about half the lethal concentration - so the classic problem for sewer workers is that if they go in where the concentration is lethal, they only smell it for a single breath or two, and then they don't realize they are in danger.

Not so for the patient who might have to undergo this suspended animation for medical reasons - they will smell it as long as they are conscious.