What is required of boxes and fittings in a Class III location?

In a Class III location, which is characterized by the presence of easily ignitable fibers or flyings, the requirement for boxes and fittings being dusttight is essential to ensure safety. Dusttight enclosures help prevent the ingress of dust and fibrous materials, which could pose a fire hazard or risk of explosion when in contact with electrical equipment.

Fittings and boxes that meet dusttight standards are designed to minimize the accumulation of combustible dust and fibers, thereby reducing the potential for ignition. This is particularly important in industrial environments or areas where materials like textiles, food, or woodworking products are processed, as the combination of electrical equipment and combustible materials increases the risk of fire or explosion.

Other options such as waterproof or only metal materials do not specifically address the hazards present in a Class III location, while standard fittings might not have the necessary protective features to ensure safe operation in such environments. Therefore, the requirement for dusttight construction directly supports the goal of maintaining a safe working area in Class III locations.