What experimental method did Louis Pasteur use to demonstrate that air and dust are sources of microbes?

Louis Pasteur used swan-neck flasks to demonstrate that air and dust are sources of microbes. He filled the flasks with broth, sterilized them, and left them open to the air. The curved necks trapped dust particles, preventing them from reaching the broth, which remained sterile until the necks were broken.

Louis Pasteur conducted experiments using flasks with elongated, swan-neck-shaped tubes. These flasks were filled with broth and sterilized by heating. The design allowed air to enter the flasks but trapped dust particles in the curved necks, preventing them from contaminating the broth. As long as the necks remained intact, the broth stayed sterile, demonstrating that microbes did not spontaneously generate but came from the air and dust. When the necks were broken, allowing dust to fall into the broth, microbial growth occurred, further supporting his conclusion.