FM Global DS 8-9: ESFR Detail — The K200, K360 and K480 Decision Matrix

This article has been rewritten from the text of FM Global Property Loss Prevention Data Sheet 8-9, "Storage of Class 1, 2, 3, 4 and Plastic Commodities" (March 2010, Interim Revision April 2026, 103 pages). The previous version contained a K-factor/pressure matrix and roof slope and skylight values compiled from other sources; they are not in the data sheet and have been removed. Every number below is given with the DS 8-9 section or table it comes from. For the commodity side see DS 8-9 Class 1-4 and plastic storage; for the in-rack side see DS 8-9 in-rack sprinklers.

1. DS 8-9 does not say "ESFR": Storage sprinklers and five attributes

Section 2.3.3.1: FM Approved sprinklers for storage hazards are listed in the Approval Guide under Storage Sprinklers, Quick-Response Storage sprinklers and In-Rack sprinklers. The revision history (Appendix B) explains that sprinkler types are now categorised as "Suppression Mode (formerly referred to as ESFR)", "Control Mode Specific Application (formerly Large-Drop)" and "Control Mode Density Area (formerly Standard)", and that the protection tables were reformatted by sprinkler type as well as commodity hazard and storage arrangement.

Section 2.3.3.7.1 bases the design on five attributes:

• K-factor: FM Approved ceiling-level Storage sprinklers range from K11.2 (160) to K33.6 (480). K8.0 (K115) and smaller, on-off, ECLH and ECOH sprinklers are not FM Approved as ceiling-level Storage sprinklers (2.3.3.2.1).
• Orientation: pendent sprinklers only in wet-pipe or antifreeze systems; upright sprinklers in wet, dry, antifreeze, preaction and refrigerated-area systems (2.3.3.2.6). Dry-pendent sprinklers only in wet or antifreeze systems (2.3.3.2.7).
• Response: quick-response thermal elements only in wet-pipe and antifreeze systems (2.3.3.2.4); standard-response in any system type (2.3.3.2.5).
• Nominal temperature: 160 °F (70 °C) in systems treated as wet; 212 °F (100 °C) where the ambient exceeds 100 °F (38 °C), treated as 70 °C for design (2.3.3.2.2); 280 °F (140 °C) in dry-pipe, refrigerated-area and equivalent systems (2.3.3.2.3).
• Spacing: standard or extended coverage (EC); the K25.2EC (K360EC) column in the tables represents extended coverage.

Section 2.3.3.6.1: install sprinklers with the same K-factor, orientation, RTI rating and temperature rating throughout the same protected area whenever possible; exceptions are in DS 2-0.

2. Table logic: "N sprinklers @ pressure", no interpolation

Section 2.3.3.7.2: the designs in Tables 2 to 11, 14a, 14b and 17b use the format "indicated number of operating sprinklers at a given minimum operating pressure"; do not interpolate or adjust the values. The table is chosen by commodity hazard, ceiling height and storage arrangement (2.3.3.7.2.1); the design can be based on any ceiling height in the table equal to or higher than the maximum ceiling height of the protected area (2.3.3.7.2.2), and a design listed for a higher ceiling may be used if it is hydraulically better (Section 2.3.3.7.1).

Section 2.3.3.7.2.3: unless sprinklers are required in every channel because of obstructed construction, the minimum design area (number of sprinklers × spacing) is 768 ft² (71 m²) for a 12-sprinkler standard-coverage or 6-sprinkler extended-coverage design, 640 ft² (60 m²) for a 10-sprinkler design and 576 ft² (54 m²) for a 9-sprinkler design; if the area is smaller, increase the number of sprinklers, but take hose demand and duration from the number in the table. Section 2.3.3.7.2.5: pendent sprinklers may also use the options listed for upright sprinklers with the same K-factor, RTI, temperature rating and spacing. The options highlighted in green in the tables are those with a 250 gpm (950 L/min) hose demand and 1-hour duration; the data sheet calls them preferable because they have the potential for less fire, smoke and water damage (Section 2.3.3.7.1).

3. Decision matrix: Table 7, wet system, quick-response pendent (Class 1-3, open-frame racks)

The values below are the "Wet System, 160 °F (70 °C), Pendent, Quick Response" columns of Table 7 (DS 8-9 p.36). Format: number of sprinklers @ psi (bar).

^a Table footnote: 8 @ 40 psi (2.8 bar) is an acceptable alternative when a 12 ft (3.6 m) maximum linear spacing is used. Table 7 also has standard-response pendent (K11.2, K14.0, K19.6, K25.2), quick- and standard-response upright and 280 °F dry-system columns; at 10.5 m and 12.0 m the dry-system cells read "See Section 2.3.6.1".

Reading the table: K200 and K240 run at 0.5-0.7 bar under low ceilings but rise to 3.5 bar (K200) from 9.0 m; K320 and K360 keep 9 @ 1.4 bar up to 9.0 m, the most economical water demand; every K-factor goes to 12 sprinklers at 10.5 m; at 12.0 m K320 and K360 return to 9 sprinklers but at 3.5 and 2.8 bar. A larger K-factor lowers the pressure, not the flow: in the same row K200 needs 12 × 200 × √3.5 ≈ 4,490 L/min while K360 needs 9 × 360 × √1.4 ≈ 3,830 L/min.

Table 8: Class 4 and cartoned unexpanded plastics (open-frame racks)

For Class 4 and cartoned unexpanded plastics the K320/K360 rows stay the same as for Class 1-3, while the K160/K200/K240 rows become markedly heavier at 4.5-7.5 m ceilings (15 @ 4.5 bar for K160 at 7.5 m). Cartoned expanded and uncartoned plastics have their own Tables 9 to 11; see the plastic storage article.

4. Ceilings over 12.2 m: Table 17b and K400/K480

Section 2.3.6.9: where the ceiling exceeds 40 ft (12.2 m), a ceiling-only system with quick-response, standard-coverage, pendent Storage sprinklers can be installed when all the conditions of Table 17b are met. The system must be wet pipe (pre-action systems designed to a wet design do not qualify, 2.3.6.9.2); racks must be open-frame (2.3.6.9.3); commodities are Class 1-4 and cartoned unexpanded plastics; cartoned expanded and all uncartoned plastics are excluded (2.3.6.9.4).

^b Can be reduced to 9 @ 40 psi (2.8 bar) when the water supply can also provide 80 psi (5.5 bar) from the most remote 4 sprinklers (2 on 2 lines). Table footnote: multiple-row racks without adequate longitudinal flue spaces need a minimum 8 ft (2.4 m) aisle. For obstructed construction Section 2.3.3.3.2 applies: Storage sprinklers located not more than 6 in (150 mm) below the underside of the structural members are equivalent to K22.4 and larger sprinklers installed not more than 13 in (325 mm) below an unobstructed ceiling.

In short, K480 (K33.6) is the DS 8-9 sprinkler for ceilings over 12.2 m and for dry systems; the wet tables at 12.2 m and below have no K33.6 column.

5. When the ceiling is higher than the table rows

Section 2.3.3.7.3: where the ceiling height exceeds the applicable table, a ceiling-only system is not an option. For rack storage (2.3.3.7.3.1): Option 1, a noncombustible false ceiling directly over and at least 15 ft (4.5 m) beyond the storage area, designed to DS 1-12, with sprinklers under it designed for the false ceiling's height above the floor; Option 2, in-rack sprinklers per Sections 2.3.4.6 and 2.3.4.7. If there is more than 20 ft (6.0 m) between the top of storage and the ceiling, in-rack sprinklers are added at the top tier, the ceiling design is taken from Table 13 for an IRAS(E) arrangement and a 6.0 m clearance, and storage on the top tier is limited to 5 ft (1.5 m). For solid-piled and palletized storage (2.3.3.7.3.2) either a false ceiling is installed or the storage is converted to racks with in-rack sprinklers.

6. Clearance, slope, venting and obstructions

• Clearance (2.2.6): at least 3 ft (0.9 m) between the top of storage and the deflectors of standard-coverage ceiling sprinklers; at least 5 ft (1.5 m) for extended-coverage sprinklers.
• Slope (Table 1, Section 2.3.3.7.2.6): DS 8-9 ties slope to the number of sprinklers per branch line in the hydraulic calculation. For standard-coverage sprinklers and 9 or fewer sprinklers, a maximum ceiling slope of 2 in 12 (10°) gives 3 sprinklers per branch line; up to 4 in 12 (18.5°) Equation 1 is used. For 10 or 12 sprinklers: 1 in 12 (5°) gives 4 where the on-line spacing is under 2.7 m, otherwise 3; 2 in 12 gives 4 under 3.0 m, otherwise 3; 4 in 12 gives 4. For 13 or more, Equation 1 up to 1 in 12, and up to 4 in 12 Equation 1 (unobstructed) or Equation 2 (obstructed). Equation 1: maximum sprinklers per branch line = (1.2 / S_avg) × (N × S_avg × L_avg)^0.5; Equation 2 uses 1.4. The data sheet gives no separate "2 % slope for ESFR" limit.
• Heat and smoke venting, draft curtains (2.1.3): DS 8-9 gives no figures and refers to DS 2-0 for areas with Storage sprinklers. Skylights are not addressed in DS 8-9.
• Obstructions and spacing (2.3.1.2, 2.3.3.3): no object between the top of storage and the ceiling sprinklers may interfere with the discharge pattern; obstruction and spacing rules are in DS 2-0.
• Extension of the hydraulic design (2.3.3.5): in mixed-use occupancies extend the design at least one branch line or sprinkler beyond all edges of the storage, or to a wall; where two adjacent storage areas are protected differently, extend the higher-hazard design one branch line or sprinkler into the lower-hazard area (Figure 2l).
• Steel columns and rack anchoring (2.1.1.3, 2.1.2): adhering to the design guidelines eliminates the need for column and overhead steel protection; racks are anchored against toppling, taking into account rack loads, absorbed sprinkler water and earthquakes (DS 1-2).

7. Hose demand, duration and water volume (Table 14)

^c When the maximum linear spacing is 12 ft (3.7 m), the hose demand can be 250 gpm and the duration 60 minutes. Section 2.3.5.1.1: allow at least 100 gpm (380 L/min) for inside hose usage and add the balance of the hose demand at the point of connection. Section 2.3.5.2: 1½ in (40 mm) small hose lines not exceeding 100 ft (30 m) must reach all storage areas.

Example, arithmetic from the table values: Table 7, 9.0 m ceiling, quick-response pendent K25.2, 9 @ 1.4 bar. Per sprinkler Q = 360 × √1.4 ≈ 426 L/min; 9 sprinklers ≈ 3,830 L/min; with 950 L/min hose ≈ 4,780 L/min; for 60 minutes ≈ 287 m³. Same row with K14.0, 12 @ 3.5 bar: 200 × √3.5 ≈ 374 L/min; 12 sprinklers ≈ 4,490 L/min; with hose ≈ 5,440 L/min; 60 minutes ≈ 326 m³. These are the minimum demands before pipe friction and elevation; the actual demand comes from the hydraulic calculation per DS 3-0, and the 54 m² minimum design area for a 9-sprinkler design applies as well.

8. Dry-pipe and similar systems

Section 2.3.2.5: the maximum water delivery time for dry-pipe and similar systems is 40 seconds, based on the most remote 4 sprinklers (2 on 2 lines) for unobstructed ceilings and the most remote 2 for obstructed ceilings; 60 seconds for cut-off areas protected by a single sprinkler. Grid-type piping is recommended only for wet-pipe and antifreeze systems (2.3.2). Dry systems use 280 °F (140 °C) standard-response upright sprinklers (2.3.3.2.3, 2.3.3.2.6). Where the ceiling exceeds 9.0 m, Section 2.3.6.1 and Tables 14a/14b apply for Class 1-3: for example at a 12.0 m ceiling K25.2 with 24 @ 15 psi (1.0 bar) (aisle ≥ 1.2 m, 25 s delivery, 1,900 L/min / 120 min) or 12 @ 50 psi (3.5 bar) (aisle ≥ 1.8 m, 20 s, 1,900 L/min / 90 min); K33.6 with 12 @ 50 psi (3.5 bar); at 15.0 m K33.6 15 @ 50 psi (aisle ≥ 2.4 m); at 16.5 m K33.6 16 @ 50 psi and 120 min. Experience shows the system size must be limited to about 12,000 ft² (1,110 m²) to achieve these delivery times, and plans must be submitted to the local FM Global office for computer analysis (2.3.6.1.5).

9. Are in-rack sprinklers needed?

Section 2.3.4.2 and Figure 3: the need for in-rack sprinklers depends on commodity hazard, ceiling height, available water supply, solid shelves or open-top containers, and flue spaces. The flowchart asks whether the racks qualify as open-frame; whether Tables 7 to 11, 14a, 14b or 17b offer a ceiling-only option and whether the water supply can meet its flow and pressure; whether open-top containers are present; whether solid shelves exceed 64 ft² (6.0 m²); and whether storage exceeds 10 ft (3.0 m) or 15 ft (4.5 m). For layouts, vertical increments and Tables 12-13 see the in-rack sprinkler article.

Field note: the first mistake with DS 8-9 is saying "we chose ESFR" and then leaving the table. The data sheet recognises a sprinkler by its attributes, not its name: for a K25.2 quick-response pendent 70 °C standard-coverage sprinkler the 9.0 m row of Table 7 reads 9 @ 1.4 bar; the same sprinkler in standard response moves to another column, and on a dry system it moves to Table 14a. The second mistake is forcing Table 7 above a 12.2 m ceiling; there Table 17b arrives with its wet-system, open-frame, 325/425 mm and 1.8/2.4 m aisle conditions together.

Quick checklist

• Commodity class assigned per DS 8-1; the most severe hazard anywhere in the area governs (2.2.2.2)
• Storage arrangement (solid-piled / palletized / rack type) and open-frame conditions (2.2.3) verified
• Ceiling height measured; the applicable table (2-11, 14a/b, 17b) and row chosen; no interpolation
• The sprinkler's five attributes match the chosen column exactly (K, orientation, RTI, temperature, spacing)
• Clearance below the deflector 0.9 m (standard) or 1.5 m (EC) provided (2.2.6)
• Minimum design area 71 / 60 / 54 m² checked (2.3.3.7.2.3)
• Sprinklers per branch line from Table 1 according to slope
• Hose demand and duration from Table 14; at least 380 L/min allowed for inside hose
• Dry systems: 40 s water delivery time and 140 °C upright sprinklers
• In-rack decision made with Figure 3

Frequently Asked Questions

Is there an ESFR table in FM DS 8-9?

There is no separate ESFR table. DS 8-9 groups ceiling sprinklers under the FM Approved "Storage sprinkler" heading and gives every design by five attributes: K-factor, orientation, response, nominal temperature and spacing. The products formerly called ESFR appear in the quick-response pendent columns of Tables 2 to 11 (K11.2 to K25.2) and, for ceilings over 12.2 m, in Table 17b (K22.4 to K33.6).

Up to what ceiling height can a K360 (K25.2) sprinkler be used on a wet system?

Table 7, quick-response pendent K25.2 column: 9 @ 20 psi (1.4 bar) from 3.0 m up to a 9.0 m ceiling; 12 @ 23 psi (1.6 bar) at 10.5 m; 9 @ 40 psi (2.8 bar) at 12.0 m. Above 12.2 m Table 17b applies: at 15.2 m, 10 @ 50 psi (3.5 bar) with the thermal element no more than 325 mm below the ceiling, or 10 @ 75 psi (5.2 bar) at 425 mm, minimum 1.8 m aisle.

When is K480 (K33.6) needed?

The wet-system Tables 2 to 11 have no K33.6 column; this K-factor appears in Table 17b for ceilings over 12.2 m (9 @ 55 psi / 3.8 bar at 15.2 m and 16.8 m) and in Tables 14a/14b for dry-pipe systems above 9.0 m (12 @ 50 psi at 12.0-13.5 m; 15 @ 50 at 15.0 m; 16 @ 50 at 16.5 m).

How much clearance is required between the top of storage and the sprinkler deflector?

Section 2.2.6: at least 3 ft (0.9 m) for standard-coverage ceiling sprinklers and at least 5 ft (1.5 m) for extended-coverage sprinklers.

How are hose demand and water supply duration determined?

Table 14: standard coverage, up to 12 sprinklers 950 L/min and 60 min; 13 to 19 sprinklers 1,900 L/min and 90 min; 20 or more 1,900 L/min and 120 min. Extended coverage, up to 6 sprinklers 950 / 60, 7 to 9 1,900 / 90 (950 / 60 when the maximum spacing is 3.7 m), 10 or more 1,900 / 120. At least 380 L/min is allowed for inside hose.

References

• FM Global Property Loss Prevention Data Sheet 8-9, Storage of Class 1, 2, 3, 4 and Plastic Commodities, March 2010, Interim Revision April 2026: Section 1.0 (p.5), 2.1.1-2.1.3 (p.9), 2.2.2 (p.10), 2.2.6 (p.26), 2.3.2 (p.26-27), 2.3.3.1-2.3.3.6 (p.27-29), 2.3.3.7 and Table 1 (p.29-31), Table 7 (p.36), Table 8 (p.37), 2.3.3.7.3 (p.40), 2.3.4.2 and Figure 3 (p.41-42), 2.3.5 and Table 14 (p.62-63), 2.3.6.1 and Tables 14a/14b (p.63-65), 2.3.6.9 and Table 17b (p.79), Appendix B (p.99)
• FM Global data sheets: fmglobal.com; related sheets DS 2-0 (installation, obstructions, venting), DS 3-0 (hydraulics), DS 8-1 (commodity classification), DS 1-12 (false ceilings)