Every living organism is in constant heat exchange with its environment and measuring the heat released from metabolism requires a very sophisticated system—the direct calorimeter. The direct air calorimeter located at the Human and Environmental Physiology Research Unit (HEPRU) at the University of Ottawa was originally developed by Jan Snellen during the 1970s at the Memorial University of Newfoundland.
A world-recognized authority in the area of human thermo-dynamics, Snellen developed one of the very few specialized whole-body calorimeters in the world at that time. This was based on a calorimeter employed by Snellen in studies conducted during his tenure in South Africa (1967–1970). It remained operational until his retirement in 1990, after which it was decommissioned. It was acquired by the director of HEPRU, Glen P. Kenny in 1998 and re-engineered and upgraded.
The main advantages of the Snellen air flow calorimeter are the fast response time, particularly for evaporative heat loss measurements, and the level of precision, particularly at high metabolic rates. With the simultaneous measurement of energy expenditure via indirect calorimetry, the Snellen calorimeter can be used to quantify the change in body heat content. Since the commissioning of the new Snellen air calorimeter, over 100 studies examining human thermoregulation have been conducted and continue to be conducted at our facilities. It is the last known operational human calorimeter in existence.
Additional details on the use of direct calorimetry and the Snellen calorimeter can be found here:
Kenny, G. P., Notley, S. R., & Gagnon, D. (2017). Direct calorimetry: a brief historical review of its use in the study of human metabolism and thermoregulation. European Journal of Applied Physiology, 117(9), 1765-1785.
See below: A gallery of photos showing the Original Snellen air flow calorimeter with J. W. Snellen looking into the partially opened chamber (image is reproduced with permission from the Paul Webb Collection, Wright University Special Collections and Archives) as well as the relocation of the Snellen calorimeter to the Human and Environmental Physiology Research Unit (HEPRU) at the University of Ottawa is provided below.
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