outlet. No result will be observed in the non-compensated flow meter, as the gas will release before reaching the tapered tube containing the float. Although Thorpe tube flowmeters are very similar in design and function to rotameters, the latter are more accurate. As a result, Thorpe tube flowmeters are often checked against rotameters to ensure their accuracy. Rotameters are also used on anaesthesia machines, where precise measurement of gas delivery is crucial to the wellbeing of the patient. Application Thorpe tube flowmeters are designed for use only on systems not supplying more than 50 PSI ( about 3 bar). The flowmeters will be labelled for the gas they are specific to. Additional color-coding may be used, for example, O2 flowmeters may have white and green labels, since white and green are respectively the Canadian and American colours identifying this gas. The flowmeter will have a safety Relief valve to relieve excess pressure. Inaccurate flow readings may occur if the device is damaged, or contaminated with water or debris. Flowmeters are only calibrated for a specified gas and will not directly read accurately on gases of different density. Changes in pressure or temperature will also affect the accuracy, and may be significant in air transport, or cities at high altitudes. Flowmeters are only calibrated in the vertical position, and for flow rates less than 15 litres per minute. See also Flow measurement References Branson, Richard D., et al. 'Respiratory Care Equipment, 2nd Edition'. Cont. Banner et al. pp. 58–62. (Philadelphia: Lippincott Williams & Wilkins, 1999). Cairo, J.M., et Pilbeam, Susan. 'Mosby's Respiratory Care Equipment'. Ed. Kelli Chronister et al. pp. 61–62. (St. Louis, Missouri: Mosby Elsevier, 2010). Wilkins, Robert L. et al. 'Egan's Fundamentals of Respiratory Care, Ninth Edition'. Ed. Lucy Kester et al. pp. 862–865, 898-899. (St. Louis, Missouri: Mosby Elsevier, 2009). Medical equipment Respiratory system procedures Respiratory therapy