Thanks, Henri, for sharing. Hoping this contractor never actually did this anywhere.
To all...
Continuing to collect, and where possible, to document these situations (esp. if actually attempted and photos are available) is important to show legislators/regulators why appropriate better oversight may be needed.
Keep us all informed as to anywhere there are efforts by, say, local radon professionals and/or public health officials to move in a positive direction of requiring things such as training, certification, licensing, and reasonable enforcement. Support for those efforts may be available. Not promising help, but if no one asks for it, it's even less likely.
Shared Crawlspace??? What's the Structure? Doesn't seem legal or wise. What about Fire code. How about the neighbor having an access point to your home. Listening or even seeing through floor openings. Creepy concept!
It is a quadraplex condo with one large crawlspace under the two lower units. No firewall.The walls of the lower level rooms are accessible from the crawlspace, and the lower level closet even has an access hatch to the crawlspace.