SJ 31470 was a Chinese electronics industry standard setting the code for the construction and acceptance of electromagnetic shielding enclosures, and it governed a category of building work that is easy to get wrong: a screened room intended for EMC measurement or for the protection of sensitive equipment is only as good as its joints, its door seals and the filters at its penetrations, and the performance can be destroyed by a single poorly made seam or by an unbonded cable entry. The standard therefore dealt with the materials and the construction of the screen, the arrangement of the seams, the treatment of doors, windows, ventilation and cable penetrations, the earthing of the enclosure and the measurement by which the finished room was accepted against a declared shielding effectiveness. The standard has since been superseded, and a project that cites it should confirm which document now applies; the measurement of shielding effectiveness itself is defined separately.