Where an electrical vault is provided for conductors and equipment operating at over 600 volts, nominal, the vault must be enclosed with a minimum 3-hour fire-rated construction in accordance with NFPA 70. The 3-hour fire-rating is permitted to be reduced to a 1-hour fire-rated construction where the vault is protected with a suppression system.

Electrical rooms also require a 2-hour fire-rated enclosure where sprinklers have been omitted from electrical rooms in buildings that are provided with complete sprinkler protection in accordance with NFPA 13. The electrical room must also comply with all additional requirements of NFPA 13 to permit sprinklers to be omitted.

It is always good idea to check with your local jurisdiction to ensure that they have not amended the code with additional fire-rating requirements for electrical rooms.