UL 823:2021 PDF Download

The UL 823:2021 standard specifies requirements for explosion-proof, dust-ignition-proof, and dust-tight portable and fixed electric heaters. These heaters are intended for installation and use in hazardous locations classified under various divisions and groups, as defined by the National Electrical Code.

The standard also covers explosion-proof electrical equipment meant for installation and use in hazardous locations classified under Class I, Zone 1, and dust-ignition-proof equipment for use in Zone 20, 21, and 22 locations. Additionally, it includes provisions for explosion-proof electrical equipment designed for specific gas or vapor atmospheres, with or without additional classification requirements.

Covered electric heaters include air heaters, hot-water or steam radiators, and hot plates rated 600 volts or less. The standard also addresses paint heaters rated 600 volts or less, with a maximum operating pressure of 100 psig (690 kPa). Paint heaters operating at pressures exceeding 100 psig may be subject to additional requirements.

It is important to note that the standard excludes medical equipment. Furthermore, it stipulates the atmospheric conditions under which the heaters may be used, including a minimum ambient temperature of minus 50 to 60°C (minus 58 to 76°F), an oxygen concentration not exceeding 21 percent by volume, and a nominal barometric pressure of one atmosphere.