FM Global DS 2-0: Automatic Sprinkler Installation Field Guide

A manufacturing plant has its sprinkler scheme drawn to NFPA 13 as light hazard. When the insurance surveyor arrives, the production line is assessed as HC-2 against the examples in FM DS 3-26 Table 2.2.2 and Appendix C; for standard sprinklers the allowable area per sprinkler drops from 20.9 m² at HC-1 to 12.1 m² at HC-2 (FM DS 2-0 Tables 2.5.2.3.1.1(a) and (b), ceilings up to 9.1 m). The result is several hundred additional sprinklers and a complete rehydraulic. This article summarises the practical content of DS 2-0: it speaks the same language as NFPA 13, but sets several critical decisions differently.

FM Approved Equipment

The fundamental rule of DS 2-0 is that sprinklers, pipe, fittings, hangers and valves must be FM Approved. Where NFPA accepts listed components generally, FM recognises only equipment carrying FM Approval. In practice this means locally certified products may be rejected by the insurer, and the procurement list must be restricted to FM Approved manufacturers.

• Sprinkler heads: FM Approved for K-factor, response index and temperature rating
• Pipe: schedule 40 black steel, or FM Approved CPVC in permitted areas only
• Joints: threaded, welded or grooved with FM Approved couplings
• Hangers: FM Approved, seismic and non-seismic
• Valves, alarm valves and dry pipe valves: from the FM Approved list

Hazard Classification

The hazard categories are defined not in DS 2-0 but in FM DS 3-26 (Fire Protection for Nonstorage Occupancies), Table 2.2.2; DS 2-0 states its installation rules in terms of those categories. They are close to, but not identical with, the NFPA light, ordinary and extra hazard classes. Design density and demand area come from DS 3-26 Table 2.3.1.10; the values below are for wet systems under ceilings up to 9 m:

• HC-1: light overall combustible loading with limited combustibles in processes — examples: residential, offices, noncombustible manufacturing, hospitals. Design: 4 mm/min over 140 m² (0.1 gpm/ft² over 1500 ft²).
• HC-2: moderate continuous combustible loading with limited plastics or ignitable liquids — examples: machine shops, woodworking, electronic assembly, retail, theatres, food production. Design: 8 mm/min over 230 m² (0.2 gpm/ft² over 2500 ft²).
• HC-3: generally continuous heavier combustible loading with heavier amounts of plastics — examples: plastic manufacturing, vehicle manufacturing and assembly, printing plants. Design: 12 mm/min over 230 m² (0.3 gpm/ft² over 2500 ft²).

In the same table the demand rises with ceiling height (for example HC-1 under a 9 to 13.5 m ceiling, wet system: 8 mm/min over 230 m²). A minimum design pressure of 0.5 bar applies at the most remote sprinkler (DS 3-26, 2.3.1.11); the hose stream allowance is 950 L/min for HC-1 and HC-2 and 1900 L/min for HC-3 (2.3.1.12); the water supply duration is 60 minutes for all categories (2.3.1.13). Storage hazards are handled separately in DS 8-9, where the design is given as sprinkler K-factor, number of operating sprinklers and pressure rather than density and area.

Sprinkler Spacing and Coverage

• Source: DS 2-0 Tables 2.5.2.3.1.1(a), (b) and (c) for nonstorage pendent and upright sprinklers under unobstructed ceilings; the values below are for ceilings up to 9.1 m
• HC-1, standard sprinklers (K80 and larger): area per sprinkler min 6.0 / max 20.9 m²; linear spacing min 2.1 / max 4.6 m (max 12.1 m² where combustible exposed vertical members are closer than 0.9 m on centres)
• HC-2, standard sprinklers: max 12.1 m²; linear spacing max 4.6 m
• HC-3, standard sprinklers: max 9.3 m²; linear spacing max 3.7 m
• Extended coverage: K14.0EC (K200EC) quick-response sprinklers reach max 37.2 m² and 6.1 m in all three categories; K11.2EC (K160EC) 37.2 m² in HC-1 and 23.8 m² / 4.9 m in HC-2 and HC-3; K25.2EC (K360EC) 18.2 m² / 4.3 m (subject to ceiling type and slope)
• Distance to walls (Fig. 2.5.2.3.2): perpendicular distance greater than 100 mm and less than 50% of the linear spacing; up to 75% at wall corners narrower than 90°

Pipe and Hangers

• Hazen-Williams C (Table 2.2.1.3.3): wet systems: black steel 120, internally galvanized 120, polymer enhanced 140, plastic 150; dry and pre-action systems: black steel 100 (120 with an inert gas such as nitrogen); vacuum systems: black steel 100 (120 when the conditions of 2.2.1.3.4 are met)
• Hanger spacing (Table 2.4.3.3.1.1): steel pipe thinner than Table 2.4.3.1.1(1): max 3.7 m for DN25–80 (not applicable above DN80); steel pipe at or above that wall thickness: 3.7 m for DN25–32, 4.6 m for DN40 and larger
• Seismic: in FM 50-year to 500-year earthquake zones (DS 1-2) the design follows DS 2-8, Earthquake Protection for Water-Based Fire Protection Systems
• Return bends and armovers: additional support against upward movement, always with grooved couplings and, with other joining methods, where the horizontal length exceeds 0.6 m (2.4.3.3.2.7 and 2.4.3.3.2.8)
• Nonmetallic pipe: nonstorage occupancies only; shielded by a fixed 15-minute-rated enclosure or FM Approved specifically as exposed pipe (2.4.1.3.2 to 2.4.1.3.4)

Practical Differences From NFPA 13

Topic	FM DS 2-0	NFPA 13
Equipment	FM Approved required	Listed acceptable
Hazard classes	HC-1/2/3 plus storage	LH, OH-1/2, EH-1/2 plus storage
Area of operation	Fixed by hazard table	Density-area curve
Hazen-Williams C (wet, black steel)	120 (Table 2.2.1.3.3)	NFPA 13 C-value table
Nonmetallic pipe	Nonstorage only; shielded, or FM Approved as exposed pipe (2.4.1.3)	Per listing scope

When FM Applies in Practice

National regulation typically accepts NFPA 13 or EN 12845 for sprinkler design, and does not reference FM data sheets directly. FM becomes the baseline through the insurance relationship:

• Plants supplying European OEMs in automotive, electronics and chemicals
• Large investors negotiating international insurance premiums
• Facilities inside an FM Global or major international insurer portfolio
• Data centres pursuing certification, where FM compliance runs alongside

Quick Checklist

• All components FM Approved
• Hazard class correctly assigned
• Sprinkler coverage and spacing within the table limits
• Hazen-Williams C-value taken from Table 2.2.1.3.3
• Hanger spacing correct for pipe size
• Seismic bracing per DS 2-8 where applicable
• Minimum design pressure achieved at the most remote sprinkler (DS 2-0 Table 2.5.1.1.2; 0.5 bar under DS 3-26)

Frequently Asked Questions

Why does FM require FM Approved equipment rather than listed products?

FM Approval is a separate testing and certification programme run by FM to its own criteria, and the insurer relies on it as evidence that the component performs as assumed in the data sheets. A product listed elsewhere may be perfectly good but has not been evaluated against those criteria, so it can be rejected at survey.

How do FM hazard classes map onto NFPA classes?

They are close but not identical. HC-1 corresponds broadly to light hazard, HC-2 to ordinary hazard and HC-3 to extra hazard, but the boundaries differ and an occupancy can sit in a higher class under FM. That is why the same building can require substantially more sprinklers under FM than under NFPA.

What is the biggest practical difference in design?

The area of operation. NFPA lets the designer move along a density-area curve, trading lower density for larger area, while FM fixes the combination by hazard class. Combined with the tighter coverage limits at HC-2 and HC-3, this often produces a denser sprinkler layout and a higher water demand.

Is FM compliance legally required?

No. National fire regulation generally accepts NFPA 13 or EN 12845 and does not reference FM data sheets. FM becomes binding commercially, through the insurance policy or through a customer's supplier requirements, which means it is a contractual obligation rather than a legal one but no less real.

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