HOLT Electricians Practice Exam

What type of enclosure is required for meters and instruments in Class I Division I locations?

1. Non-metallic enclosures

2. Explosion-proof or purged enclosures

3. Standard enclosures will suffice

4. Sealed wooden enclosures

The correct answer is: Explosion-proof or purged enclosures

In Class I Division I locations, which are characterized by the presence of flammable gases or vapors, the enclosures used for meters and instruments must be specifically designed to prevent ignition of these materials. Explosion-proof or purged enclosures are built to contain any explosion that may occur within the enclosure itself, thus preventing the propagation of the explosion to the surrounding atmosphere. These enclosures are constructed to withstand the pressure of an internal explosion and are capable of preventing the release of ignitable gases from escaping. This means that even in the event of equipment failure or a fault condition, any potential sources of ignition are effectively managed, ensuring safety in environments where flammable materials are present. Standard enclosures, on the other hand, do not provide the necessary protection against ignition sources in hazardous locations, and non-metallic or sealed wooden enclosures also do not afford the requisite reliability and safety measures needed for Class I Division I areas. Therefore, the requirement for explosion-proof or purged enclosures is critical in such locations to protect personnel and equipment from hazardous conditions.