Smelling Generator Exhaust

[Viva Las Vegas JDR]

Within about 15 or 20 minutes of starting the genny, the carbon monoxide alarm on the wall was going off and the smell of exhaust fumes was evident. We shut the generator down and opened all the windows to ventilate our newell. Not fun with 40 degree outside temps.

I started checking today for somewhere that the exhaust might be getting in and couldn't find any breaches in the floor area etc. Where should I check, carbon monoxide is very dangerous and not something taken lightly which is why I want to get this resolved asap.

JDR