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The correct answer is that ENT, or Electrical Nonmetallic Tubing, should not be installed in plenum spaces. Plenum spaces are areas utilized for air circulation in heating, ventilation, and air conditioning (HVAC) systems. These spaces are typically above ceilings or below floors, and they can carry heated or cooled air throughout a building.
One of the primary concerns with using ENT in plenum spaces is that it is not rated for fire resistance or low-smoke production. If a fire were to ignite in these spaces, materials that do not meet fire-resistance standards could contribute to the spread of flames and produce toxic smoke, posing risks to life safety and property. Therefore, the National Electrical Code (NEC) has established strict regulations that prohibit the use of ENT in these areas to mitigate such risks.
The other options, while they present scenarios where caution might be needed, do not align as strictly with the code regulations regarding ENT installation. For example, while ENT may face limitations in high-temperature environments, specific ratings and guidelines exist that can allow for variation based on the materials and conditions. Similarly, general building applications and areas with potential fire hazards may allow for different types of installation and materials that meet the required safety standards, unlike plenum