Thermal radiation is the way that high-temperature objects radiate heat directly to the outside. It does not need direct contact or any medium, and can also be transmitted in vacuum. Many firefighters have been burned even when the protective devices are not degraded or hardly degraded. Therefore, in the high-temperature fire environment, thermal radiation is the main cause of firefighters’ burns. The anti-heat radiation performance and heat insulation performance of fire-fighting fabrics are very important to protect firefighters’ life safety, so fire-fighting fabrics used in high temperature environment must have anti-heat radiation performance.
Heat radiation resistant tools meeting AQ 6103, BS EN 366:1993, DIN EN 366:1993, ISO 6942:2002 and other standards are used to measure the thermal radiation protection performance of protective materials.
The test device consists of radiation device, sample support, data acquisition and software system. The sample rack can move horizontally, and the heat radiation flux can be determined by different positions. Data acquisition system, which can automatically record thermal radiation flux, temperature, time and other parameters. Equipped with computers and printers, data can be output freely, which is convenient and fast.

More details please refer to https://www.firetestingequipment.com/protective-clothing-protection-against-heat-and-fire.html