Initial field evaluation of the Harvard active ozone sampler for personal ozone monitoring

Assessing personal exposure to ozone has only been feasible recently with t he introduction of passive ozone samplers. These devices are easy to use, b ut changes in air velocity across their collection surfaces can affect perf ormance. The Harvard active ozone sampler (AS) was developed in response to problems with the passive methods. This active sampler has been tested ext ensively as a microenvironmental sampler. To test for personal sampling, 40 children attending summer day-camp in Riverside, California wore the activ e ozone sampler for approximately 2.6 h on July 19 and 21, 1994. when ozone concentrations were about 100 ppb and 140 ppb. respectively. The children spent 94-100% of the sampling period outside, staying within a well-defined area while participating in normal camp activities. Ambient ozone concentr ations across this area were monitored by two UV photometric ozone monitors . The active sampler was worn in a small backpack that was also equipped wi th a passive ozone sampler. Device precision. reported as the percent diffe rence between duplicate pairs of samplers, was +/- 3.7% and +/- 4.2% for th e active and passive samplers. respectively. The active sampler measured, o n average, 94.5 +/- 8.2% of the ambient ozone while the passive samplers me asured, on average, 124.5 +/- 18.8%. The samplers were worn successfully fo r the entire sampling period by all participating children.