National Fire Protection Association (NFPA) is a global nonprofit standards-writing organization devoted to eliminating death, injury, property, and economic loss due to fire, electrical, and related hazards. Their document, NFPA 780 — Standard for the Installation of Lightning Protection Systems, is recognized as the basis for lightning protection systems in North America. The standard can now be read online and without charge by clicking here.
When determining how to incorporate lightning protection into new or existing structure designs, it is recommended that contractors, architects, and engineers engage the services of a specialty contractor with experience implementing the requirements of NFPA 780 and UL96A. However, here are a few questions we are often asked about standards for lightning protection systems and NFPA 780:
What is NFPA 780?
NFPA 780 is the industry-standard to follow when designing and installing lightning protection systems and components. NFPA 780 details the necessary considerations for installing lightning protection for ordinary structures and a variety of special applications. NFPA 780 is a consensus standard that has been maintained since 1904. It is updated every three years to incorporate technological advances and innovations in building materials. NFPA 780 provides the information required to protect people and property against fire risks and related dangers that can occur when a structure is exposed to a lightning strike.
According to NFPA 780, what type of structures should be considered for lightning protection?
Any and all structures have the potential to be struck by lightning – commercial, industrial, and public buildings, as well as residential building types. NFPA 780 provides detailed guidance on installing lightning protection systems in ordinary structures and special occupancies, including masts, spires, and flagpoles, facilities that handle or process combustible/explosive dust, metal towers and tanks, air-inflated structures, concrete tanks and silos, guyed structures, rooftop helipads, and fabric structures. The publication also provides instructions for protecting heavy-duty stacks, structures containing flammable vapors, gasses or liquids, or other explosive materials, wind turbines, watercraft, airfield lighting circuits, solar arrays, and more.
What determines the placement of lightning protection equipment on a structure?
NFPA defines zones of protection on a structure, based on the geometry of the structure and known behaviors of lightning as it approaches Earth. Lightning protection system designers utilize the rolling sphere method to help determine where air terminals or strike termination devices are required on rooftops or other parts of a building. To simulate how lightning might interact with a structure, lightning protection system designers utilize software to create a sphere with a 150-foot radius rolling over the surface of a building from all directions. Because it is assumed that lightning has an electrically charged field emanating approximately 300 feet from the bolt, lightning can strike in any location where the sphere touches the surface of a building. This includes roof edges and corners, roof-top equipment, and projections from the sides of buildings, such as balconies and gable ends.
For referrals to lightning protection specialty contractors with expertise in implementing NFPA780-compliant systems, please contact ECLE.