Smoke coming through air vents

[Ben]

On the way to work this morning I started getting smoke coming though the air vents. I've often thought that I have a certain amount of exhaust fumes coming into the car as the air never seems as fresh as outside, but its never done this before.

I'd only just left home, so the engine wouldn't have been hot, so couldn't have been burning leaked diesel etc, and I was doing 70mph, so surely any fumes in the bay would have been blown about elsewhere.

So I thought the problem may infact be steam coming from the matrix. But the coolant wouldn't have been hot and my heating doesn't work anyway.

So basically I've ruled out the only ideas I had, and really need some help, because aside from possibly being gassed, I can't clear the windscreen even with the blowers on full!