Which of the following are acceptable hazardous (classified) location protection techniques for electrical and electronic equipment? I. Purged and Pressurized II. Oil Immersion III. Raintight Enclosure

• A. II only
• B. II or III only
• C. I, II, or III
• D. I or II only

Answer: (D)

Understanding how to protect electrical equipment in classified locations starts with addressing the risk of ignition from flammable atmospheres. Purged and Pressurized protection works by maintaining a positive pressure of an inert gas around the equipment, so any potentially flammable vapors are kept out and cannot ignite energized parts. Oil Immersion protection submerges the equipment in oil, isolating hot surfaces and internal components from surrounding vapors and preventing ignition. A raintight enclosure, while effective at keeping rain out, does not address ignition risk in hazardous atmospheres and thus isn’t sufficient on its own for classified locations. So the acceptable techniques are Purged and Pressurized or Oil Immersion.