In support of Health Effects Research Studies, pulmonary function tests are periodically administered to a large number of children. The ventilatory performance of these children is being evaluated by measuring the 0.75-sec forced expiratory volume (FEVo.75) with a waterless mechanical volume spirometer used in conjunction with an electronic timing unit. During a 1-yr testing period, operation with the volume spirometer and the EPA designed electronic timing unit proved to be highly successful. The volume spirometer was found to be more advantageous in conducting tests at remote field stations than the water spirometer and other electronic instruments which measure flow rate with a transducer element. The volume spirometer is lightweight, easy to operate, and has the capability of easy and accurate field calibration when used in conjunction with the electronic timing unit. Presently the volume spirometer and EPA designed electronic timing package are employed in all Community Health and Surveillance System (CHESS) pulmonary function testing studies.