2012 Toyota Prius Owners Manual - Page 632

3-1. Using the air conditioning system and defogger Defogging the windshield Press . The air conditioning system control operates automatically. Recirculated air mode will automatically switch to outside air mode. Micro dust and pollen filter Press . Outside air mode switches to recirculated air mode. Pollen is removed from the air and the air flows to the upper part of the body. Usually the system will turn off automatically approximately 3 minutes later. To stop the operation, press again. 330