The normal range of EtCO2 is between 32-45mmHg, about 5%. Both mainstream and sidestream modules can measure up to 150mmHg (about 20%), and the respiratory rate can measure up to 150 times/minute. The measurement accuracy calculated in brief is as follows: • 0 – 40mmHg ±2mmHg • 41 – 60mmHg ±5% of the reading • 71 – 100mmHg ±8% of the reading • 101 – 150mmHg ±10% of the reading.