Smokey mist from heater outlet.

Travelling thro the M25 road works - steady 50mph -early this morning suddenly noticed a smokey mist from the heater outlets. Engine temp ok, heater not on but screen tending to mist up. Smokey mist gave me a scare and I quickly altered all the heater settings to see if it made any difference, I don't think it did.
The smokey mist disappeared of it's own accord leaving me baffled, it had no smell and the coolant level was unchanged, car uses no oil. Have since covered some 60 miles without it happening again and it has never happened before.
Any ideas please?

Heater Matrix??? keep an eye on the coolant level!

. . . . . . spooky .. . . .. :jaw:

It's trying to burn itself

Do you have aircon? It can sometimes cause a similar effect if the air is particularly humid.

I have often seen a similar effect on aircraft - quite un-nerving as it looks as if the cabin is filling with smoke

Its the aircon,

I've only ever seen it in a Ford Ranger, as it reached the top of a seriously steep hill, looks impressive

Many thanks for all the comments / suggestions. Looks like the aircon theory is the answer.
Covered the same journey today with no problems so hopefully wont meet it again.

dunt this tie in with the lady who had her air con recharged by kwik ****, and was told she may see some smoke coming out following the recharge ?

http://www.landyzone.co.uk/lz/f16/just-had-my-air-con-serviced-regassed-but-no-cold-air-108727.html