My car book says to roll down the windows to let out all the hot air before turning on AC.
                      
WHY ?
Car Air Conditioning - No wonder more folks are dying from cancer than ever before. We wonder where this stuff comes from but here is an example that explains a lot of the cancer causing incidents.    
                      
Many people are in their cars first thing in the morning and the last thing at night, 7 days a week.
As I read this, it makes me feel guilty and ill.  Please pass this on to as many people as possible.  Guess it’s not too late to make some changes.
                    
Please do NOT turn on AC as soon as you enter the car.
                      
Open the windows after you enter your car and then turn ON the AC after a couple of minutes of driving.
                      
Here's why:   According to research, the car dashboard, seats, air freshener emit Benzene, a Cancer causing toxin (carcinogen - take time to observe the smell of heated plastic in your car).
                      
In addition to causing cancer, Benzene poisons your bones, causes anemia and reduces white blood cells. Prolonged exposure will cause Leukemia, increasing the risk of cancer. Can also cause miscarriage.
                    
Acceptable Benzene level indoors is 50 mg per sq. ft. A car parked indoors with windows closed will contain 400-800 mg of Benzene.
If parked outdoors under the sun at a temperature above 60 degrees F, the Benzene level goes up to 2000-4000 mg, 40 times the acceptable level.

People who get into the car, keeping windows closed will inevitably inhale, in quick succession, excessive amounts of the toxin.


Benzene is a toxin that affects your kidney and liver. What's worse, it is extremely difficult for your body to expel this toxic stuff.
                      
So friends, please open the windows and door of your car - give time for interior to air out -dispel the deadly stuff - before you enter.
                      
                      
This is what  snopes.com  says.  It is not the air conditioning in the car but the Benzene producing agents that cause cancer. http://www.snopes.com/medical/toxins/benzene.asp