This standard provides uniform measurement procedures for determining the shielding effectiveness of electromagnetic (EM) shielding for a variety of enclosures and boxes having all dimensions between 0.1 and 2 meters in the radio frequency range not addressed by IEEE 299. This standard is divided into two parts: Part I - physically small, but electrically large enclosures and Part II - 0.75 to 2 meters. In addition to a number of annexes aiding the measurement of shielding effectiveness of these enclosures, Annex J addresses physically small and electrically small enclosures, and Annex K addressed electrically small enclosures in reverberation chambers. Problems occurring in the testing of small enclosures, having linear dimension less than 2 meters, are very different from determining the shielding effectiveness of large rooms and broad depending of the actual size of the enclosure itself. A number of other annexes are included that address rationale, mathematical formulas, selection of measurement techniques, preliminary measurement and repairs, wall-mounted monopoles, impedance mismatch correction, and using isolated monopoles in outer reverberation chambers.