Beckman got in touch with a Caltech professor who was working on smog, Arie Jan Haagen-Smit. They developed an apparatus to collect particulate matter from Los Angeles air, using a system of tubing intermittently cooled by liquid nitrogen. Haagen-Smit identified the substance they collected as a peroxy organic material. He agreed to spend a year studying the chemistry of smog. His results, presented in 1952, identified ozone and hydrocarbons from smokestacks, refineries and car exhausts as key ingredients in the formation of smog.