Doo-Doo Vapor is a substance which, although not deadly, is very unpleasant and should be avoided at all costs. Doo-Doo Vapor occurs when somebody has decided to take a shower but also has to take a dump (in a bathroom where the toilet and shower are in the same room).
If this person makes the mistake of taking the dump first, flushes and then gets ready to take a shower, everything seems fine. However, when the shower has started, the steam created by the hot water binds with tiny floating objects referred to in the scientific community as "doo-doo particles". After a few minutes, the person in the shower is now surrounded by air that smells like shit and is breathing it in. A valuable lesson is learned.
Millions of people a year come in contact with Doo-Doo Vapor. If you enter a bathroom that has doo-doo vapor in the air, exit immediately and scorn whoever took a shit and a shower one after the other before you.