ISO 17554:2014 specifies a small-scale method for assessing the mass loss rate of essentially flat specimens exposed in the horizontal orientation to controlled levels of radiant heating with an external igniter under well-ventilated conditions. The mass loss rate is determined by measurement of the specimen mass and is derived numerically. The time to ignition (sustained flaming) is also measured in this test. Mass loss rate can be used as an indirect measure of heat release rate for many products. However, this is not an apparatus for determining heat release rates, and the measured mass loss rates for some products are not so closely linked to their heat release rates. Such products need to be tested in accordance with ISO 5660-1 for correct assessment of heat release.