From Consalazio CF, Energy expenditure studies in military populations using Kofranyi-Michaelis respirometers, The American Journal of Clinical Nutrition, December 1971, page 1432.

“This simplified and compact unit is fairly small, 20 by 27 by 11 cm, weighs 3 kg, and consists of a dry gas meter for measuring the total volume and temperature of expired air. The aliquoting device can eb set to continuously remove 0.3 or 0.6% of each breath of expired air into a 500-ml butyl rubber bag. One important feature is that these aliquots can be taken over fairly long periods of time. These aliquots are analyzed for their CO2 and O2 concentration by conventional procedures and the eventual calculation of energy expenditure.”