Handbook of Dangerous Materials

Circular of the Bureau of Standards no. 565:

“…Glass etching is done with hydrofluoric acid because it attacks glass quite rapidly either in solution or in the gaseous state. It is also potent on human, beings and will destroy living tissue [17]. If it is handled with the fingers, it will cause hard-to-heal sores and will work its way under the fingernails, where it is hard to get at to neutralize.…”

Analytical methods used in geochemical exploration by the U.S. Geological Survey

“…The vapor is extremely irritating to the respiratory tract, causing congestion of the lungs. As little as 50 ppm of the vapor in air may be fatal in an exposure of 30 to 60 minutes (Sax, 1951). Other volatile substances are dangerous because chronic poisoning results from continued exposure to relatively low concentrations.…”

Some effects of recent volcanic ash falls, with especial reference to Alaska

“…The accompanying list gives the maximum concentration of industrial gases considered permissible for workers in steady contact (Sax, 1951), but somewhat greater concentrations of some of the gases can be tolerated for short periods of time. Thus, while 10 parts per million of sulfur dioxide is regarded as the maximum allowable concentration for continuous exposure, as much as 50 to 100 parts per million can be tolerated for exposures of half an hour to one hour duration.…”