Warehouse fires are hard to fight because the ceiling is high and the stored goods burn fast. NFPA 13 therefore has three main sprinkler approaches for storage: CMDA and CMSA aim to control the fire, while ESFR aims to suppress it.
The short answer
- CMDA (control mode density/area): wets and cools the fire to control it until responders arrive. Sized from density/area curves, NFPA 13 Chapter 21.
- CMSA (control mode specific application): also controls, with a large K-factor and a special deflector. No density/area curves; NFPA 13 Chapter 22.
- ESFR (early suppression fast response): activates quickly and attacks the fire directly to extinguish it. NFPA 13 Chapter 23.
Side by side
| CMDA | CMSA | ESFR | |
|---|---|---|---|
| Goal | Control | Control | Suppression |
| Design basis | Density/area curves | NFPA 13 decision tables; flow and pressure from several variables | NFPA 13 decision tables; flow and pressure from several variables |
| K-factor | Larger than standard sprinklers | K-11.2 minimum | Large K-factor, fast-response element |
| System type | Per listing | Wet, dry or preaction, per listing | Wet systems only |
| Coverage per sprinkler | Per NFPA 13 Chapters 20-21 | 80 to 130 sq ft | 64 to 100 sq ft; spacing not over 12 ft |
| Typical design area | From the density/area curve | Rectangle; branch-line side at least 1.2 times the square root of the area | 12 hydraulically most demanding sprinklers (four on each of three lines) |
CMDA: familiar, but built for storage
CMDA sprinklers look and spray much like standard commercial sprinklers. The difference is mainly a larger K-factor and higher temperature ratings. The required flow and pressure come from density/area curves, so the design method will feel familiar to anyone who has sized ordinary hazard systems.
CMSA: control with a larger orifice
CMSA sprinklers have large K-factors, at least K-11.2 for plume penetration, and a special deflector that produces different droplet sizes and spray patterns for high-challenge storage. They need a different listing from CMDA. Water demand depends on pile height, ceiling clearance, pile stability and storage array, and obstructions that disturb the discharge pattern should be avoided.
ESFR: suppression from the ceiling
ESFR sprinklers are used for high-piled storage of Class I-IV commodities, Group A plastics, rubber tires, rolled paper and similar. They are listed for wet systems only. Points that often decide a design:
- Ceiling-only ESFR cannot protect storage on solid shelf racks or in open-top containers.
- Keep 36 inches between the sprinkler deflector and the top of storage.
- Next to a standard-response system, a noncombustible draft curtain at least 2 feet deep is required, with a 4-foot clear aisle centered below it.
- Under NFPA 13-2016 and later, K-14 ESFR sprinklers are no longer permitted in buildings over 35 feet; K-16.8 is the direct replacement with the same hydraulic requirements.
What drives the choice
Selection depends on commodity class (I-IV plus plastics), storage arrangement (rack, solid-piled or palletized), ceiling height and whether goods are encapsulated in plastic, which raises water demand and limits stacking. Where ceiling-level protection is not enough, in-rack sprinklers are fitted inside the racks, usually with cage guards and water shields.
Try it on your own layout
Our storage sprinkler selector checks Reliable and Tyco ESFR and standard sprinklers against your ceiling and storage height and calculates flow. For the full scope of work, see our fire protection services.
Sources
- Design of fire sprinkler systems for high-piled storage (Consulting-Specifying Engineer)
- The basics of CMDA, CMSA and ESFR storage sprinklers (QRFS)