NFPA - National Fire Protection Association
The NFPA 79-2018 (Electrical Standard for Industrial Machinery) is an important standard for the electrical equipment of machines on the US market. It requires industrial machines containing safety interlock circuits to be equipped with SPDs to protect against the effects of surges caused by lightning discharges or switching operations. The SPD type used must be suitable for the location of the industrial machine and must be a UL listed device according to the 4th edition of UL 1449. You can find out here which DEHN devices are suitable for use in industrial machines in the USA.