Gas smell outside when furnace comes on

[Javeman]

I've noticed that I can strongly smell gas if I'm standing outside by the vent when the furnace comes on. It goes away after maybe 10 seconds until the next time the furnace comes on again. Is this something I should be concerned about?

[speedway84]

I would contact my local gas utility if this was happening.

[Munchos]

You are most likely smelling aldehydes, a byproduct of incomplete combustion. Every time the furnace fires up, it is always a rough combustion process, hence why you are smelling it only on start-up. Just a warning though that this smell is also a very easy indicator of a bad heat exchanger.