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The air comes from the air outside and the air conditioning system in the car turns this into cold or warm air.
The 1939 Packard was the first car with a true air-conditioning system.
Automotive air conditioning is the ac unit in your car. It's what "conditions" the air in your car, ie keeping the temperature inside the car cool or warm.
No use for exhaust in car air conditioning
The purpose of the AC vent hose in a car's air conditioning system is to carry cold air from the air conditioning unit to the vents inside the car, allowing the cold air to be distributed throughout the interior of the vehicle.
No, it is not safe to use propane in a car's air conditioning system. Propane is highly flammable and can pose a serious safety risk if used in place of the recommended refrigerant. It is important to use the proper type of refrigerant for your car's air conditioning system to ensure safe and efficient operation.
Take the car to a garage that services AC. There is costly equipment and knowledge needed to do AC work correctly.
No cars "need" air conditioning. It is a personal preference of the owner. Most people would want air conditioning in their car as an option. Mississippi's hottest day was 115 degrees!
For most cars the air conditioning is powered by a belt from the engine and even if the car is only idling it will be running without any meaningful effect on the car's battery. For some hybrid drive cars the air conditioning is powered electrically, so that it can work even with the engine off. These will drain the car's battery some, but the air conditioning controller will automatically turn off the air conditioning before this becomes a problem then turn it back on as soon as the engine is automatically restarted when it is again needed to drive the car.
changes the air temperature inside
I am not sure what the national chain is where you can get the air conditioning in your car serviced. Ask your car manufacture or your local garage or ask family and friends.