Flame-retardant insulation is required for which of the following?

Flame-retardant insulation is specifically required for raceways due to the potential for raceways to be used in various environmental conditions where they may be exposed to heat or fire. The purpose of using flame-retardant materials is to minimize the risk of fire spreading along the raceway or through adjacent materials. Raceways, which may house electrical conductors and equipment, can serve as pathways that lead to multiple points within a building, making fire safety a critical concern.

The use of flame-retardant materials ensures that in the event of a fire, the insulation around these raceways contributes to limiting the propagation of fire, thereby protecting both the electrical infrastructure and the overall safety of the building. The National Electrical Code mandates such materials in specific applications to enhance safety and reduce hazards associated with electrical installations. This requirement emphasizes the importance of understanding and implementing safety measures in electrical installations per the code's guidelines.