After watching HBO’s hit show Chernobyl, the last thing you’d want to find in your house is a sign that says “Warning. Do not enter. Poison Gas.” To the OP’s utter shock, that’s what they found in a crawlspace in their home from the 80s next to three red boxes encased in concrete. The whole situation was so ominous that even the local media got involved.
It reached a point where radiation control inspectors were called in to examine the site. Thankfully, they didn’t find anything dangerous. The warning label turned out to be from the 1950s and the boxes didn’t have anything important either…not anymore anyway.