Coffee beans are roasted with heated air in a roasting chamber, and contaminant-laden exhaust air including caffeine entrained therein is discharged from the chamber. While roasting is in progress, the exhaust air from the chamber is heated, directed through a catalytic converter and cooled to a temperature between about 250.degree. F. to 325.degree. F. Thereafter the cooled exhaust air flows through a cooler or condenser where the temperature of the cooled exhaust air is further lowered to between about 100.degree. F. and 155.degree. F., and it is then directed through a HEPA filter to remove caffeine particles that are present in the cooled air. Substantially caffeine-free clean exhaust air can then be discharged from the HEPA filter directly to the surroundings of the roasting machine such as a closed room, e.g. a retail establishment, frequented by persons.