300.21 Fire-Rated Walls, Ceilings, and Floors – https://www.MikeHolt.com/code. Wherever there’s airflow, the potential for a fire to spread exists. The requirements in section 300.21 of the NEC are designed to prevent, as much as possible, increasing the spread of fire where electrical installations may decrease fire-resistive ratings of walls, ceilings, and floors. In this podcast, you’ll learn what must be done in order to comply with this rule.