A Chemical Called Mercaptan Is Added To Natural Gas,

the reason being that natural gas is odourless,

to help people recognise the smell, scratch-and-sniff cards were sent out to the general public in Great Falls, Cascade County, Montana, in the United States, all went well until workers at Energy West who were cleaning out some storage areas found several discarded boxes of scratch-and-sniff cards, Nick Bohr, general manager at Energy West explained, 'they were expired, and they were old, they threw them into the dumpsters', the problem was that when the cards were picked up by sanitation trucks and crushed, 'it was the same as if they had scratched them',

then the problems really started as the trucks drove around the downtown area, it left behind the smell people think of as natural gas, 'it’s really, really potent', said Jamie Jackson, a battalion chief for Great Falls Fire/Rescue, it smells like rotten eggs and is not poisonous, but as the smell wafted into downtown buildings, so emergency crews responded to several reports of gas leaks Wednesday morning, and numerous buildings were evacuated,


Bohr said the company apologises for the problem, especially since the smelly culprits originally were just part of a process to make everything safer, 'in a sense, it worked the way it was supposed to', Bohr said of the numerous calls reporting gas leaks, 


I would never have thought that the sniff and scratch cards would have been so powerful, still I guess this might be a way for a perfume manufacturer to give everyone a free sample of one their products, just think of the money a local council could make, the bin lorries crushing out of date sniff and scratch perfume cards with mobile sales shop following the bin lorries!