Cyanide ion (CN-) and sulfuric acid produce HCN, a highly toxic gas. When inhaled, HCN interferes with celllular respiration and can lead to what amounts to molecular-level suffocation.
I am grateful to the writer and editors at the Oregonian for giving specifics on this accident. So often I see vague references in the media to spills or accidents involving chemicals, without actually naming them. As in, "a tanker turned over and spilled a toxic chemical...." ammonia? chlorine? xylene? The consequences of such spills can vary dramatically.
Good eye for the person who noticed the foaming, too. The evolution of the gas seems to have tipped him off to the fact that something was amiss.
Anybody know what they do with cyanide in a chip factory?