[BenV]

But the 'smell' of natural gas is an added in compound, so that we can better identify it. I don't think the gas itself has any odour.

Sorry, yes Ben you're quite right, and I didn't state that quite correctly. We're very sensitive to the smell that is put into gas, which is why it's used. But do you know what the smell is?

Fair enough.  The odouriser is (according to wikipedia) t-butyl mercaptan, or sometimes thiophane.

[Mazurka]

...

I find Parmesan cheese weird; I like it, on the right meals, but to me it smells like vomit on it's own.

Parmesan and some other cheeses (I am unsure if Camembert does) and things like anchovies and seaweed are rich in Umami which has its own receptor on the tongue.  This makes it the 5 th “taste” alongside sweet, salty, sour & bitter. 

Food's effect comes from the combination in your brain of the 5 tastes on the tongue and the smell in your nose. (which is why food does not “taste” a great deal if you smoke or have a cold.)

Umami is fascinating and is often described as giving things a hearty or “brown” taste and is basically Monosodium glutamate (MSG). I believe it was first "identified" in the early 20thC by a bloke in Japan curious about why seaweed soup tasted so good.  In a blind taste test (with nose plugs) good parmesan is practically indistinguishable from  MSG.
(I love the BBC R4 Food programme for the occasional scientific titbit about food)

[blakestyger]

But the 'smell' of natural gas is an added in compound, so that we can better identify it. I don't think the gas itself has any odour.

They add t-butyl mercaptan - it's harmless but easily detected in low concentrations.

[Bored chemist]

But the 'smell' of natural gas is an added in compound, so that we can better identify it. I don't think the gas itself has any odour.

They add t-butyl mercaptan - it's harmless but easily detected in low concentrations.

Or ethanethiol. I guess it depends what's cheap at the time.