The NFPA 750 (2019) Standard for Water Mist Fire Protection Systems is a guideline published by the National Fire Protection Association (NFPA) that establishes requirements for the design, installation, testing, maintenance, and performance of water mist fire suppression systems. These systems use fine water droplets (mist) to control, suppress, or extinguish fires, offering advantages such as reduced water usage, minimal collateral damage, and effectiveness in specialized applications where traditional sprinklers may not be suitable.
Key Features of NFPA 750 (2019):
1. Purpose: Ensure water mist systems are reliable and effective for fire protection in diverse occupancies (e.g., commercial, industrial, marine, historical buildings, data centers). Address Class A (ordinary combustibles), Class B (flammable liquids), and Class C (electrical) fires.
2. Definition of Water Mist: Droplets with 99% of the volume (Dv0.99) ≤ 1,000 microns (1 mm) in diameter. Systems classified by pressure: Low pressure (< 12.1 bar / 175 psi), Intermediate pressure (12.1–34.5 bar / 175–500 psi), High pressure (> 34.5 bar / 500 psi).
3. System Requirements: Design Approaches: Prescriptive: Follow predefined rules for nozzle spacing, flow rates, and water supply. Performance-Based: Use engineering analysis to meet fire suppression goals. Components: Pumps, nozzles, piping, and valves must be listed/certified for water mist use. Water Supply: Adequate pressure, flow, and duration to suppress fires (e.g., 30–60 minutes for buildings).
4. Applications: Suitable for unique hazards (e.g., turbines, machinery spaces, archives, electrical equipment). Safe for occupied spaces (minimizes oxygen displacement risks compared to gas systems).
5. Safety and Integration: Must coordinate with fire detection, alarms, and ventilation systems. Addresses visibility concerns during discharge (e.g., reduced visibility in escape routes).
6. Installation & Maintenance: Follows NFPA 25 for inspections, testing, and maintenance. Requires post-installation testing (e.g., flow rates, nozzle functionality).
Why It Matters:
Water mist systems are ideal for sensitive environments (e.g., museums, data centers) and high-risk areas (e.g., offshore platforms, power plants). NFPA 750 ensures these systems meet rigorous safety and performance standards while balancing efficiency and water conservation.
For full compliance, engineers and installers must adhere to the standard's technical details and reference related codes like NFPA 25 (Maintenance) and NFPA 13 (Sprinkler Systems).