Smog story (California Institute of Technology), 1950
Caption slip reads: "Photographer: Hecht. Date: 11-17. Reporter: Harrison. Assignment: Smog story -- Caltech. 17: Doctor A.J. Haagen-Smit holds inflated toy balloon in stream of ozone-hydrocarbon fumes. Oxidation of rubber caused it to burst in a few seconds. 142-143: In his laboratory, Doctor A.J. Haagen-Smit produces one of the commonest kinds of smog product of ozone and hydrocarbons".