An apparatus to calibrate the system of measuring O 2 consumption and CO 2 production has been developed for premature infants. This system is based on the alcohol combustion principal. The alcohol combustion is used to test the indirect calorimetric system due to its simplicity and reliability. In the previous studies, the O 2 consumption rate of alcoholic combustion is too large to simulate the breath of premature infants. A new design is proposed to burn alcohol continuously at a rate as low as 0.004 ml min Ϫ1 , equivalent to an O 2 consumption rate of only 3.9 ml min Ϫ1 , a level in the breath range of preterms of about 660 g based on the measurement 5.9 ml kg Ϫ1 min Ϫ1. The alcohol combusts with various steady-state rates to imitate the breath of premature infants, and it is useful for a canopy open-circuit system. The calibration tool proposed here would be helpful in the clinical study of energy expenditure for preterms.