Investigation of an Ambient Interference in the Measurement of Ozone by Ultraviolet Absorption Photometry

An unusually high apparent ozone concentration was measured with an ultraviolet absorption ozone monitor when a plume from the burning of forest slash was traversed during an aerial ozone monitoring experiment. A similar result was observed in a laboratory experiment in which air containing the effluent from the pyrolysis of conifer needles was sampled by the UV ozone monitor. This effect was determined to arise from UV-absorbing gases in the effluent. These results indicate the undesirability of using the UV absorption ozone instrument in plume studies where the instrument can be exposed to transient concentrations of gases that can absorb 254-nm wavelength light.