fogged crystals of a car

Hello very good
I have a problem with a Suzuki Vitara that at the time three people climb that cars begins to tarnish the crystals inside and with the given air it does not detach neither with cold or hot air, what can it have to make it tarnish so fast and do not leave? I have been told that it is probably from the heating and ventilation system that is not very good but in the workshop they found nothing
very much

If you have nothing clean the crystals with an anti -mapant to solve the problem the samnucas are small and if you come from a soccer match the car that is tarnish the vidriio luck.

Thank you very much you know the name of any product of those that is quite efficient at the time of the application?

In almost all automotive supplies houses, at least here in Chile, they sell are a kind of creams that clean the glass and protect from the fog.