Sounds like a fascinating account of things people rarely think about. A friend's father worked on the construction of the Hoover Dam and he had a story of seeing one worker fall into the concrete as it was being poured. *shudder*

My brother works for the water company, and early on part of his job was climbing in the crawlspaces underneath reservoirs. He carried a mechanical "canary" which would warn if the air was bad. Job duties most people have no idea exist.