What is the main requirement for equipment installed in Zone 0?

The main requirement for equipment installed in Zone 0 is that it must meet stringent electrical safety standards. Zone 0 refers to areas where there is a constant risk of electric shock due to the presence of water, which could create electrical hazards. To ensure safety in such environments, the National Electrical Code (NEC) mandates that electrical equipment operating in these exceptionally hazardous zones must not only be constructed to withstand conditions such as moisture but also be designed to minimize the risk of electrical shock. This involves adhering to specific standards that often include being submersible, having suitable ingress protection ratings, and passing particular performance tests to ensure device safety when submerged in water.

Other options do not align with the rigorous safety requirements. Equipment deemed to be resistant to rust (the first choice) doesn't capture the breadth of safety needs regarding electrical shock prevention and environmental conditions. The idea that any equipment can be used as long as it is labeled (the third choice) undermines the necessity for thoroughly vetted safety features, while the assertion that such equipment does not require special consideration (the fourth choice) contradicts the fundamental principles of ensuring user safety in high-risk zones.