Visiting properties, yesterday, with new clients.
One of them went down to the basement, and called up the stairs "There's a strong smell of gas down here".
My first thought, of course, is to respond "I haven't even been in the basement yet. It wasn't me!" I barely managed to keep from blurting that out.
I followed downstairs, and sure enough... a very strong smell of natural gas emanating from the furnace room. Clearly a gas leak on the furnace or the pipes serving the furnace. Not a good thing, and as this was a vacant property, I immediately notified the listing agent, and we exited the property quickly.
The listing agent was grateful (although I'm sure I interrupted his dinner), as I would have been, too. It's hard to sell a home that's been reduced to a smoldering crater surrounded by police tape. Not impossible, mind you, but much harder.
If I hadn't been able to reach the agent, I would have contacted the local gas company's emergency hotline right away. This is the sort of thing that has caused houses to explode taking neighbouring homes with it.