"Results of the continuing stratospheric flight test evaluation program for the Del Model I Electrostatic Precipitator Sampler and the Del Electrical Discharge Altimeter are described and discussed. Only one of four balloon launches reached floating altitude. The altimeter obtained an altitude recording consistent with concurrent aneroid barocoder readings. The reported gross gamma concentration for the precipitator sampler was approximates 25 and 80% higher than those of the two simultaneous direct flow filter samples. The completion of the design and construction of two prototype units of the Del Electrical Discharge Altimeter and their laboratory evaluation are described. A preliminary design concept is presented for an operational high volume electrostatic precipitator sampler to operate with high collection efficiency at an ambient flowrate of 500 cfm throughout the altitude range 100,000 to 150,000 ft."