Nick Weaver, client sector technical manager, recently represented Team Henderson at the 2023 NFPA Conference & Expo. The event brings together a diverse group of fire, electrical, and life safety professionals to learn, network, evaluate suppliers and their products, and participate in the code development process. There is still much to learn about how we can improve fire protection designs. The world is ever evolving and the hazards we face in the fire protection industry continue to evolve as well. Nick returned with the following key takeaways: 

Effect of Roof Pitch & Ceiling Structures on Fires 

Not all standards used for fire sprinkler design are established based on full-scale testing. In fact, FM Global Data Sheet 2-0, Installation Guidelines for Automatic Sprinklers, based sprinkler design standards for obstructed construction on a series of reduced-scale fire tests. To confirm current design requirements, FM Global utilized computer modeling to validate the requirements and/or determine if the requirements could be modified. Results from the modeling were as expected – unobstructed construction was not a challenge for the current design guideline, and obstructed construction (24 in. deep purlins) resulted in significant channeling. 

FM took their testing a step further and conducted full-scale fire testing for three different purlin depths (12 in., 18 in., and 24 in.) with cartoned unexpanded plastics. The results of each test reflected results comparable to the baseline tests. More information was needed for uncartoned unexpanded plastics. 

Additional full-scale fire testing was done with uncartoned unexpanded plastics stored beneath obstructed construction – results were not comparable to baseline tests. Computer modeling suggested that closing the gap created where purlins and girders intersect would help to reduce the channeling effect. Based on the testing, new guidelines are expected to require sprinklers to be within 6 in. below maximum 18 in. deep structural members where ceiling slope does not exceed 1 in 12. 

Where structural members are less than or equal to 24 in., channels must be “blocked” to limit pockets to no more than 400 cubic feet, and ceiling slope shall not exceed 1 in 12. Where structural members exceed 24 in., sprinkler must be installed in every channel. Additional updates to Data Sheet 2-0 will be released based on additional testing specific to sloped roofs. 

Lithium-Ion Batteries & Battery Fire and Fire Explosion Hazards 

Risk of fire due to lithium-ion batteries is a growing hazard based on the extensive use of these batteries in so many of our commonly used electronic devices. These include cell phones, tablets, electric toothbrushes, tools, scooters, e-bikes, and solar power backup storage. Larger energy storage systems (ESS), typically used residentially, commercially, or by utilities, can be found mounted to the ground or in/on outside walls, outside cabinets, garage walls, basements, utility/storage closets, walk-in enclosures, and battery rooms or dedicated-use buildings. 

Lithium-ion batteries consist of a cathode, an anode, an electrolyte, and a separator, which prevents the cathode (on one side) and the electrolyte and anode (on the other side) from making contact. These batteries come in three different formats – pouch, prismatic or cylindrical, each having their own benefits and drawbacks from a safety perspective. Safety features can range from vents, switches, fuses, or circuitry for small battery systems to gas and smoke detection systems and/or fire/explosion control for larger energy storage systems. Energy storage systems come in the same three formats as lithium-ion batteries and include the following components: cells/modules/racks, battery management system (BMS)/energy storage management system (ESMS), thermal management (air or liquid), power conditioning systems (inverter), fire/explosion control, communications, uninterruptible power supply (UPS), and an enclosure. 

Lithium-ion batteries can fall into a condition known as thermal runaway for several reasons including environmental effects, mechanical failures, impact, improper charging, or aging. Thermal runaway is when an electrochemical cell increases its temperature through self-heating in an uncontrollable fashion – the cell’s generation of heat is at a higher rate than the heat it can dissipate. It is a cyclical process whereby the temperature rises causing an increased reaction rate and heat generation with some heat dissipation (less than what is generated). It occurs when there is a breakdown or failure of the separator between the battery’s cathode and electrolyte. 

Thermal runaway results in cell-to-cell propagation, and the release of flammable gases. This continues until propagation stops or ignition occurs. Hazards include sudden flaming, sudden explosion, and/or toxic exposure. Dry chemical is ineffective for any type of Lithium-ion related extinguishment, and water is the most effective portable extinguishing agent. Enclosures, however, may negate the benefit of spraying water at a battery pack. 

The International Fire Code, NFPA Standards 13, 15, 68, 69 and 855 provide guidance regarding fire and explosion protection of energy storage systems. Options for explosion control include deflagration venting (NFPA 68) in the form of blow-out panels, deflagration prevention per NFPA 69 utilizing an exhaust system to maintain a Lower Explosive Limit (LEL) of less than 25% in the area, or an engineered cabinet may be used. 

Energy storage standard UL 9540 provides for a “system” listing (or certification), which allows for a listed battery and inverter, and defines construction and performance, mechanical and environmental tests, communications systems, function safety, and HVAC, and includes requirements for UL9540a fire testing. The purpose behind requiring UL9540a fire testing is to determine if thermal runaway can be induced, and if so, document thermal runaway methodology and instrumentation, determine cell surface temperature at venting and thermal runaway, and measure gas generation and composition. 

Significant ESS failures have led to the safety of these systems being in the spotlight – explosions at two locations, a utility failure, and recalls. Thermal runaway prevention, detection, and suppression remain critical gaps. 

Henderson Knows Fire & Life Safety 

Henderson fire protection engineers know design, life safety technology, and construction. Our diverse group of fire protection specialists includes licensed engineers with backgrounds in fire protection, mechanical, chemical, civil, and architectural engineering; NICET certified technicians; and fire service professionals. We provide thought leadership and expertise on multiple code and standards technical committees for the Society of Fire Protection Engineers (SFPE), National Fire Protection Association (NFPA), and other national organizations. Click here to learn more.