"ABSTRACT An ozone sampling device has been developed which can monitor exposure concentrations in the personal ""micro-environment"" under typical ambient exposure conditions@ for periods from less than one hour to several hours. The device consists of a personal air-sampling pump@ a light-tight chemically unreactive filter holder@ and a filter paper impregnated with a binary ozone-reactive organic reagent. It was shown to perform adequately in exposure chamber tests at ozone concentrations from 0.05 to 0.25 ppm@ and in field testing by volunteers exercising outdoors on typical southern California summer afternoons. Further research under other support will include testing of the device over a wider range of temperature and humidity@ and design modifications to facilitate passive sampling@ i.e. eliminate the pump. An inexpensive heart rate recorder was demonstrated to be useful in monitoring physical activity of volunteer outdoor workers over periods up to 16 hours. Heart rate records were most often consistent with volunteers' self-reporting of activity in diaries@ but some diary entries appeared to overestimate or underestimate activity. A combination of heart rate and diary records appears to be the most satisfactory means of estimating ventilation during typical daily activities. Relationships between heart rate and ventilation rate were directly measured in the same volunteers during supervised indoor and outdoor exercise. Heart rate/ventilation relationships vary somewhat within and between individuals@ but are consistent enough to be useful in estimating ventilation."