Oxygen consumption calorimetry has made the measurement of heat release rate of a fire a routine part of fire testing for both research and for regulatory compliance. Heat release rate is a primary metric of fire size which is foundational in modern fire protection engineering. The device allows a sample to be exposed to different heat fluxes over its surface. Its name comes from the conical shape of the radiant heater that produces a nearly uniform heat flux over the surface of the sample under study.