"Nancy2" > wrote in message

That's a smell here in the US that is like rotten eggs (sulphur) -

I have a new furnace, vented outside and drawing air directly from
outside, so that's not a worry, but I have a gas water heater, which
could certainly cause some problems. I tend not to worry about that
stuff.

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That smell is for gas. CO has no odor and that is what makes it so
dangerous if there is a leak.
Gas is fuel. CO is in the exhaust.