Three cars were set up to donate the exhaust. The first vehicle did not have any catalyst, the second vehicle was equipped with a malfunctioning three-way catalyst, and the third vehicle was equipped with a well-functioning three-way catalyst. The three different starting situations were cold, tepid, and warm engine start, respectively. Measurements of CO concentrations were made in the cabin and in the exhaust pipe. Lethal CO concentrations were measured in the cabin using all three vehicles. In most cases, the mathematical model gave good predictions of CO concentrations in the cabin. Measurements showed differences among vehicles in transient CO emissions from the engine and indicated it would be possible to commit suicide by CO poisoning using a car equipped with a catalytic converter. An appendix describes the mathematical model. 13 references, 1 table, and 10 figures