Schoffelen & Plasqui explained the application area’s in their 2017 paper: “Classical experiments in whole-body metabolism: open-circuit respirometry—diluted flow chamber, hood, or facemask systems”.

Since the construction of the first room calorimeter more than 150 years ago, calorimeters have developed over time from labor-intensive machines that analyzed gases chemically to contemporary automated systems that continuously analyzed gases and processed data online. Faster response times and improved sample resolutions brought forth by these technological developments have opened up the area to a wide range of applications. Human energy metabolism has been studied using room calorimeters and is still being studied today in a variety of environmental settings.

Most popular application areas for Indirect Calorimetry

Numerous studies examined the metabolic response to various food products by manipulating the quantity of food, the proportional contribution of the three main substrates—carbohydrates, lipids, and proteins—or the reaction to the so-called thermogenic substances, like tea extracts or capsaicin (red pepper extract). The study of human metabolism when exposure to cold (or heat) has sparked a new interest in thermal physiology with the identification of brown adipose tissue in adult humans.

The study of sleep and circadian rhythms and their impact on human metabolism has also grown in importance given the modern global society we live in, where people can stay in touch with one another around the clock, frequently travel through time zones, and are exposed to screen light from their electronic devices almost constantly. Others have investigated the impact of the seasons, ethnic diversity, or EE during pregnancy.

Modern calorimeters have the ability to examine EE almost instantly, even in a big volume like a room calorimeter, therefore the controlled environment also presents excellent opportunities for exercise investigations. Recent research has demonstrated that even VO2-max testing is feasible in an 18 m3 room calorimeter. Additionally, the increased time resolution makes it easier to conduct validation tests on various wearable sensors to see how well they can predict energy expenditure.

There are many more applications and these study subjects represent just a small portion of the work that has been done. Room calorimeters are the perfect tool for studying metabolism in tightly controlled environments since they allow for the regulation of all food intake, temperature, humidity, illumination, and even oxygen pressure, as well as the measurement of human EE and substrate oxidation.

Focus on facemask, ventilated hood, or respiration chamber

This article primarily focused on the open-circuit diluted flow principle, which can be utilized with a facemask, ventilated hood, or respiration chamber, out of the various indirect calorimetry approaches that are now available. In a bypass flow that can be adjusted depending on the degree of gas exchange, i.e., from sleeping metabolic rate to VO2max, all exhaled air is caught and diluted. One benefit is that there are no flow limits at the mouth brought on by flowmeters or valves.

The open-circuit diluted flow approach can be seen as a contemporary upgrade to the full-capture calorimeters of the past for bedside and exercise applications. These applications, which trade high volumes for quick response and make use of contemporary whole-room calorimetric equipment, are now possible because to advancements in electronics and analyser accuracy. The use of indirect calorimeters is not as simple as the less experienced user may anticipate. It demands specialized knowledge, appropriate and frequent validation, and painstaking attention to detail for outcomes that are dependable and accurate.

Related products

Whole body room calorimeters

The Room Calorimeter offers the highest validated accuracy and reproducibility in the market. Designed on a system level out of the highest quality components, this is the gold standard for energy expenditure studies of any kind; 24-hr energy expenditure, high intensity exercise testing and many more. Validated and applied in 100’s of research studies.

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The Omnical is the market’s most versatile and accurate indirect calorimeter for research. It allows users to conduct investigations in a variety of study sectors using cutting-edge technology and top-of-the-line precision measurement devices. The system is designed to monitor energy metabolism with great precision, ranging from resting metabolic rate (RMR) through sports performance testing (e.g. VO2max tests).

Omnical RMR / BMR

Omnical Sport

How can we help you with your research?

Maastricht Instruments creates equipment in the field for indirect calorimetry measurements. We provide support for studies, research and measurements alongside our indirect calorimetry products.

Consult us about our indirect calorimetry metabolic  cart,  whole room calorimeter  systems or  accelerometry  add-ons. Please  contact us or find more information on our information pages.


Schoffelen, P.F.M., Plasqui, G. Classical experiments in whole-body metabolism: open-circuit respirometry—diluted flow chamber, hood, or facemask systems. Eur J Appl Physiol 118, 33–49 (2018).