Can you smell weed?

I read a story in the local paper today about a suspected cannabis factory that had burnt down in the area. Police found plants and weed-growing paraphernalia at the house once the fire had been put out so it’s a fair bet that the place was being used to grow puff. To be honest though, I’m surprised the police needed to find any evidence to know what had been going on in the house. I’d have thought the smell of all that burning weed and half the neighbourhood walking around eating mars bars would have given the game away….