Pasteur disproved the idea that living things could just appear by his experiment. It involved boiled water with nutrients in flask w narrow neck and regular flask. In regular flask, there were microorganisms when exposed to air. The narrow-neck flask, there was no microorganism as it could not get in through the neck. Without the narrow neck, water in the same flask had microorganisms when exposed to air.
It was not the air but particles in air that had microorganisms.