NOTE This Section specifies fixed and semi-fixed foam fire suppression systems used to extinguish or control fires involving flammable and combustible liquids. (1.1)

NOTE The systems covered protect a fundamentally different fire than ordinary water-based sprinkler systems. A flammable-liquid fire is extinguished not by cooling but by a stable foam blanket that floats on the fuel surface, excluding oxygen and suppressing the release of flammable vapor. Because the agent, the discharge devices, and the proportioning equipment all differ from water systems, foam suppression is specified as its own discipline. (1.2)

NOTE The work of this Section includes foam concentrate, proportioning equipment, discharge devices, concentrate storage, detection and actuation interfaces, and acceptance testing. (1.3)

NOTE A complete foam system is an assembly of matched components: a listed concentrate, a proportioner that injects that concentrate into the water stream at the correct ratio, piping that carries the solution, and discharge devices that aspirate and apply the finished foam. Substituting any one component without verifying compatibility with the others is the most common source of system failure. (1.4)

NOTE System types covered by this Section. (1.5)

NOTE This Section addresses the following foam system types, each suited to a distinct hazard geometry: (1.6)

NOTE Water-only deluge and pre-action sprinkler systems are not part of this Section. (1.7)

NOTE Deluge valves, releasing panels, and water-only spray coverage are specified in Pre Action And Deluge Sprinkler Systems. Where a foam-water system shares a deluge valve or releasing panel with a water system, that shared hardware is coordinated with that Section. (1.8)

NOTE Gaseous clean-agent total-flooding systems are not part of this Section. (1.9)

NOTE CO2, inert-gas, and halocarbon clean-agent systems are specified in Clean Agent Fire Suppression. Foam and clean agents are not interchangeable; the hazard analysis selects one or the other. (1.10)

NOTE Fire pumps, hydrants, fire department connections, and fuel gas piping are not part of this Section. (1.11)

NOTE Dedicated foam-system water supply pumps, drivers, and controllers are specified in Fire Pumps. Fire hydrants are specified in Fire Hydrants, fire department connections in Fire Department Connections, and fuel gas and LP-gas piping in Fuel Gas Piping. Structural spill-containment dikes and berms are civil/structural scope and are not specified here. (1.12)

NOTE Edition adoption matters more for foam than for most disciplines because NFPA 11 (2021) absorbed most of the former NFPA 16 content into a new Chapter 6, while NFPA 16 (2019) remains independently adopted in some jurisdictions. Designing to NFPA 16 in a jurisdiction that has adopted NFPA 11 Chapter 6 - or the reverse - produces conflicting requirements. Confirm which document governs at project outset. (2.4)

NOTE The market is in the middle of a regulatory transition away from per- and polyfluoroalkyl substances (PFAS). Multiple states - including California, Washington, and Minnesota among others - prohibit new aqueous film-forming foam (AFFF) installations as of the 2024-2026 window, and the FAA Reauthorization Act of 2024 and the DoD AFFF phase-out (extended to September 30, 2025 for fixed systems) drive replacement toward fluorine-free foam (F3). Specifying AFFF without confirming local PFAS restrictions is the most common and most expensive error in current foam design, because the concentrate may be banned by the time the project is permitted. (3.3)

NOTE AFFF, alcohol-resistant AFFF (AR-AFFF), fluoroprotein (FP), and fluorine-free foam (F3) are chemically distinct and are not interchangeable. Mixing incompatible concentrates, or charging a system with a concentrate other than the one the proportioner and discharge devices were sized for, can degrade foam quality below the listing threshold. A concentrate change requires re-verifying proportioner ratio, storage volume, and discharge-device aspiration. (3.5)

NOTE F3 foams (also marketed as Synthetic Fluorine-Free Foam, SFFF, or FFF) can exhibit lower burn-back resistance than AFFF on some hydrocarbon hazards, and manufacturer data frequently calls for application rates increased 10-25% over the AFFF baseline. A 1:1 substitution that keeps the AFFF design density can leave the hazard under-protected. (3.7)

NOTE UL 162 is the listing basis for foam equipment and concentrates and defines the foam-quality tests - expansion ratio and 25% drainage time - that determine whether a discharge device produces an acceptable foam blanket. Components not listed together as a system are not a system. (5.4)

NOTE A frequent error is pursuing only the local building permit while overlooking that new or modified foam systems at airports require separate FAA approval. The two approvals are sequential, and missing the FAA step stalls the project at permit. (5.7)

NOTE The group classification governs whether the hangar uses a low-expansion foam-water system over the floor or a high-expansion total-flooding system, and it drives the structural and drainage coordination. Establishing the group late forces a system-type change that ripples through the entire design. (5.9)

NOTE Most AFFF concentrates are rated for storage between 35°F and 120°F (2°C to 49°C); F3 concentrates vary by manufacturer. Concentrate stored outside its rated range can stratify or lose performance, and frozen concentrate is unusable. (6.3)

NOTE Foam concentrate - AFFF in particular - is corrosive to ordinary carbon steel. Specifying standard carbon-steel concentrate piping is a recurring defect that leads to early failure. (6.6)

NOTE Discharged foam solution is regulated as hazardous waste in many jurisdictions and cannot be allowed to enter stormwater. The spill control and secondary containment required by NFPA 30 must be coordinated with the site drainage design before the system is approved. Failing to coordinate drainage and containment is a common cause of approval delay. (6.8)

NOTE There is no universal foam system. A surface fire on an open spill is handled differently from a fire inside a fixed-roof tank, which is handled differently again from a fire in an enclosed hangar. The configuration below is the primary design fork, and it determines the discharge devices, the proportioner sizing, and the application rate tables that apply. (7.2)

NOTE NFPA 11 classifies foam by how much the finished foam expands relative to the foam solution: low expansion is less than 20:1, medium expansion is 20:1 to 200:1, and high expansion is 200:1 to 1,000:1. The expansion band follows from the system type and the discharge device; it is not independently selected. (7.4)

NOTE Foam makers apply low-expansion foam to tank surfaces, high-expansion generators flood enclosed volumes, foam-water sprinklers and open spray nozzles cover deluge areas, and monitors or cannons project foam across open-air fuel-handling areas. Each device aspirates and expands the foam differently, so the device, the concentrate, and the proportioner must be a listed match. (7.6)

NOTE The proportioner injects concentrate into the water stream at the design ratio. The available methods - inline balanced-pressure, bladder-tank, around-the-pump, variable-flow balanced-pressure, and premixed storage - differ in how they hold ratio as flow changes. A balanced-pressure proportioner sized for a large flow will not hold ratio when only a fraction of the deluge heads operate, so the full flow-range analysis, not just the peak flow, governs the selection. (8.2)

NOTE For a 3% system this means the delivered concentration shall remain between 2.1% and 3.9% across minimum, design, and maximum flow. A proportioner that meets accuracy only at peak flow but starves the foam at low flow does not satisfy this requirement. (8.4)

NOTE Under-sizing concentrate storage is a frequent and costly RFI: storage volume calculated at 1% when the system is designed at 3% leaves only a third of the required concentrate. Size the bladder tank or concentrate tank for the design percentage multiplied by the design solution flow and the full required application time, plus the manufacturer's reserve. (8.6)

NOTE Application rate is the heart of foam design. For low-expansion surface application on hydrocarbons, NFPA 11 Table 5.3.3.1 sets a minimum of 0.10 gpm/ft²; most designs land between 0.10 and 0.16 gpm/ft² depending on hazard category. Foam-water sprinkler systems under NFPA 16 use a minimum of 0.16 gpm/ft² over the design area. High-expansion total flooding for aircraft hangars is sized by floor-area fill rate per NFPA 409 Table 5.2.1, typically 1.0 to 2.0 cfm/ft² at a 10:1 expansion ratio. The values below are the common design cases; the governing table for the actual hazard always controls. (9.2)

NOTE The application rate and the application time together fix the concentrate storage volume. Selecting the rate without the matching time, or vice versa, produces a storage tank that is too small for the design event. (9.4)

NOTE Group III and IV hangars are typically protected by high-expansion generators sized for a one-foot-per-minute fill rate or as approved by the AHJ. The group classification, established earlier in Quality Assurance, selects which of these rules applies. (9.6)

NOTE Foam systems may actuate automatically on heat, flame, or gas detection, or by manual means only, and automatic releasing may be single-interlock or cross-zoned. The releasing devices interface with the fire alarm and detection system, and the division of work between the foam installer and the fire alarm contractor must be fixed in the coordination matrix. Leaving this interface ambiguous is a reliable generator of RFIs. (10.2)

NOTE A foam system can share the site fire main or use a dedicated supply, but in either case the supply must satisfy the proportioner's inlet pressure requirement simultaneously with all other demands during the design event. Bladder-tank proportioners in particular impose an inlet-pressure requirement that a shared main may not meet under concurrent demand. Where a dedicated foam-system pump is required, it is sized and specified under Fire Pumps. (11.2)

NOTE Residual foam solution left standing in piping accelerates corrosion and can foul discharge devices. Provide drains at low points and a means to flush the system after each discharge. (12.2)

NOTE Foam relies on a continuous floating blanket; a discharge device aimed into a column, a duct, or stored equipment leaves an unprotected pocket. Coordinate device locations with the structural and equipment layout. Device locations, routing, and protected-area extents are shown on the drawings foam system layout. (12.5)

NOTE Acceptance testing proves two independent things: that the proportioner delivers concentrate at the correct ratio, and that the discharge devices produce foam of acceptable quality. Both are required; a system that proportions correctly but produces poor foam, or produces good foam at the wrong ratio, fails. (13.2)

NOTE Testing at a single flow point does not demonstrate the ±30% accuracy required across the operating range. The three-point test catches proportioners that hold ratio at design flow but drift at the extremes. (13.4)

NOTE A 25% drainage time faster than 4 minutes indicates a thin, unstable blanket that will not hold the vapor down. (13.7)

NOTE Foam concentrate degrades over time and the warranty period for the agent is distinct from the system installation warranty. The owner needs the manufacturer's recommended retest interval to keep the agent within its listed performance over the system's life. (15.3)

NOTE A foam system that has discharged is out of service until it is recharged. Providing a full recharge volume of the installed concentrate type and percentage returns the system to service without waiting on a concentrate order. (16.2)