An automated exposure system for human inhalation study

The authors developed a computer-based exposure system for human inhalation research to study the toxicokinetics of gases. The system uses a set of computer-controlled solenoid valves that regulates inhaled gases and collect exhaled breaths from the subject in accordance with a predetermined time schedule. The volunteer's breathing activity is monitored simultaneously with a real-time instrument, calibrated by both internal and external standards. The common air pollutant, 1,3-butadiene, was used for system validation. The results indicated that the errors were less than 3% relative to reference standards, and the error in the timing of the valve operation was negligible. The average difference between breath-monitoring methods was within 10%. The proposed system is an easy-to-use, reliable device for human studies; more than 130 subjects were tested in a companion study.