[kehrlann]

Nothing gets scrutinized - it's illegal to go down there anyway. Folks down there are not always safety conscious or very responsible :o)

Sometimes there are parties with tens or over a hundred people in a big room that only has two crawl holes to exit it.

About fire safety, well it's pretty damp down there, mostly with rocks and dirt. Can't picture a whole room catching fire... But I'm no expert in fire safety.

[adrianN]

In a place with sufficiently tight exits like the crawl holes you mentioned, it is enough if there is a little smoke to cause a panic. People will die from being trampled even if there is no actual danger from the fire.

[kehrlann]

Home-made smoke bombs are a classic (and annoying) prank in the underground. Fills an entire gallery in less than a minute: https://www.loupiote.com/photos_l/catacombes-de-paris-cataco...

Parties I was talking about look like this: https://youtu.be/6E-F-cVqubU

[jacquesm]

Gas leak... depending on how far down you are, old gas lines tend to leak little bits of gas because they get porous that can pool.

[kehrlann]

Never heard of such an incident in the catacombs before.

In my uninformed opinion, this seems unlikely: gas pipes in Paris are buried less than 1m deep, whereas the catacombs are 10 to 30m underground, below service galleries for utilities, sewers, and even the subway.