In a building with 500 sprinkler heads, how many extra sprinkler heads must be maintained as spares?

In a building equipped with 500 sprinkler heads, the National Fire Protection Association (NFPA) guidelines, particularly NFPA 25, suggest maintaining extra sprinkler heads as spares. The requirement is generally to have a minimum of 12 spare sprinkler heads for systems with between 300 and 1,000 heads.

This practice is crucial for ensuring that any malfunctioning or damaged sprinkler heads can be quickly replaced to maintain the integrity and effectiveness of the fire suppression system. By having these spare parts readily available, a building can minimize disruption in safety protocols and ensure that fire protection measures remain fully operational, which is essential for life safety and compliance with regulations.

The other options suggest different quantities that do not align with the NFPA recommendation for buildings with 500 heads, making 12 the most appropriate and compliant choice.