Heat Flow below 100°K and Its Technical Applications covers the proceedings of the International Institute of Refrigeration. This release serves the purpose of compiling supplementary materials to the published report by Committee 3, entitled Protection against Ionizing Radiation from External Sources. This text is a compilation of 12 appendices that comprise information for employing the recommendations of ICRP Publication 15. These appendices relate to the sources of external radiation encountered in medical, dental, and veterinary radiology, as well as in industry and research. Some of the information included are on the collision stopping power of charged particles; interpolated values of quality factor; and quality factor as a function of charged particle energy. This compendium then presents materials on conversion factors, neutron sources and shielding, and range-energy curves. The last two materials cover the shielding for beta sources and X-ray and gamma-ray shielding. This compilation will cater those interested in the technical applications of heat flow, as well as to those who have read the ICRP Publication 15 and in need of supplementary materials.