A 20-min protocol was then used to train participants in the decision-making task. A technician trained in administering this test was present to answer questions before the test, and could enter the chamber to answer questions during the test. We estimated that CO 2 emissions of the technician, who was in the chamber for about 10 min during each session, would increase chamber CO 2 concentrations by no more than 17 ppm. (The technician was not required to give informed consent for this because the study conditions are commonly experienced in indoor environments and are not associated with adverse health effects.) Over the next hr, participants took the computerized test of decision-making performance, which involved reading text displayed on a laptop computer and selecting among possible responses to indicate their decisions.