If the combined capacity of common supply and return air systems exceeds 2,000 cfm, what is required?

When the combined capacity of common supply and return air systems exceeds 2,000 cubic feet per minute (cfm), the installation of smoke detectors becomes a crucial requirement. This is primarily due to safety considerations in mechanical systems, especially in larger buildings or complex HVAC installations.

Smoke detectors are essential for early detection of fire hazards within the air handling system. They help ensure that in the event of smoke or fire, the HVAC system can react appropriately—for instance, by shutting down to prevent smoke from spreading throughout the building via the air ducts.

This requirement aligns with safety codes and standards that seek to minimize risk to occupants in buildings with significant air circulation. Regular maintenance, air purifiers, and filtered air systems, while important for overall system performance and indoor air quality, do not fulfill the specific safety function that smoke detectors provide in high-capacity air systems.