𝗤𝘂𝗶𝗰𝗸 𝗖𝗵𝗮𝗻𝗴𝗲 𝗧𝗶𝗽 𝗼𝗳 𝘁𝗵𝗲 𝗪𝗲𝗲𝗸: Closing the windows and choosing the recirculation setting of the car’s ventilation system reduces particulate matter concentration. The recirculation button simply takes the air from inside the car and recirculates it in the cabin instead of pulling polluted air from outside.