Which of the following defines "hazardous locations" in electrical installations?

The term "hazardous locations" refers specifically to environments that pose an increased risk of fire or explosion due to the presence of flammable gases, vapors, or dust. This definition is crucial for electrical installations, as these conditions can significantly affect the safety requirements and standards that must be adhered to when designing, installing, and maintaining electrical systems. Areas identified as hazardous typically require specialized equipment and installation practices to mitigate the risks associated with these potentially explosive atmospheres.

In contrast, the other options do not accurately describe hazardous locations. Areas with high voltage equipment alone do not necessarily correlate with a higher risk of fire or explosion; thus, they are not classified as hazardous locations exclusively based on voltage levels. Cursory inspections are insufficient for environments that present significant hazards; thorough and regular inspections are necessary to ensure safety. Lastly, limiting hazardous locations to indoors overlooks the fact that potentially dangerous environments can exist outdoors, such as in refineries or chemical plants, making it critical to assess both indoor and outdoor scenarios.