IMPROPERLY STORED OR

PROTECTED PALLETS CAN

PRESENT A SIGNIFICANT

FUEL LOAD AND CAN LEAD

TO A CATASTROPHIC LOSS

IN THE EVENT OF A FIRE.

1Willis North America | February 2014

IDLE PALLET STORAGE FIRE HAZARDSIdle wood and plastic pallets are found in many facilities; however, the serious fire hazards they pose often are not understood. Improperly stored or protected pallets can present a significant fuel load and can lead to a catastrophic loss in the event of a fire.

Pallets have open spaces between their slats that allow for the free flow of air. This construction allows heat from burning surfaces to radiate toward each other, intensifying fire, while hindering water from the sprinkler system from reaching the seat of the fire.

The heat-release rates of pallet fires is high, making idle pallet fires difficult to control. Increasing the storage height of pallets just a few feet dramatically increases the heat-release rate of the fire. Plastics have 2 – 2½ times (16 – 20,000 Btu/lb.) more heat content than wood, making plastic pallets an even greater hazard. In some facilities, idle pallets are the most challenging fire hazard for the sprinkler system.

PALLET STORAGE LOCATIONSThe number of idle pallets should be limited to the minimum amount needed. Figure 1 shows, in order of preference, the recommended locations for idle pallet storage.

Outdoor pallet storage is preferable. A fence with a gate(s) should prevent access of unauthorized persons and afford access to the fire department. Long narrow piles are preferred over large square piles to facilitate manual fire fighting. (The short dimensions increase the effectiveness of hose streams and ease pile breakdown). Aisles should be maintained between individual piles, between piles and buildings and between piles and the boundary line of the storage site to permit fire department access to all portions of the storage area. Aisles should be at least twice the pile height to reduce the spread of fire from pile to pile.

TECHNICAL ADVISORY BULLETINRISK CONTROL AND CLAIM ADVOCACY PRACTICE

February 2014 www.willis.com

Willis North America | February 20142

Figure 1

MAIN BUILDING

Cut-Off Room

Cut-Off Room

Cut-Off Room

Detached Low-Value Building

Outdoor Storage1

5

2

3

4 20’Min.

Distance per Table 1

Table 1 – Distance of Outdoor Idle Pallet Storage from Exposed Buildings and Yard Storage

Wall Construction Minimum Distance [ft (m)] of Wall from Storage of

Type of Wall Openings Under 50 Pallets 50 to 200 Pallets Over 200 Pallets

Masonry

Wood/Approved

Plastic

Plastic Wood/Approved

Plastic

Plastic Wood/Approved

Plastic

Plastic

None 0 6 (2) 0 20 (6.1) 0 30 (9.1)Wired Glass with Outside Sprinklers and 1-hour doors

0 8 (2.4) 10 (3.1) 24 (7.4) 20 (6.1) 40 (12)

Plain Glass with Outside Sprinklers and ¾-hour Doors

10 (3.1) 15 (4.5) 20 (6.1) 40 (12) 30 (9.1) 100 (30)

Wood or Metal with Outside Sprinklers 10 (3.1) 15 (4.5) 20 (6.1) 40 (12) 30 (9.1) 100 (30)Wood, Metal or Other 20 (6.1) 30 (9.1) 30 (9.1) 80 (24) 50 (15.2) 150 (45)Separation Between Piles of Pallets and Other Yard Storage

15 (4.5) 30 (9.1) 30 (9.1) 80 (24) 90 (27) 150 (45)

Other considerations:

� Provide fire resistive protection comparable to that of the wall for combustible eave lines, vent openings, etc.

� When pallets are stored close to a building, restrict the height of storage to prevent burning pallets from falling on the building.

� Manual outside open sprinklers are not a reliable means of protection unless a property is attended at all times by plant emergency personnel.

� Open sprinklers controlled by a deluge valve are preferred.

3Willis North America | February 2014

PALLET TYPESBesides wood pallets, there are two types of plastic pallets. Regular plastic pallets present a greater challenge to sprinkler systems than wood pallets, while plastic pallets that are UL listed or FM approved are considered to present the same fire hazard as wood pallets.

WOOD AND UL LISTED OR FM APPROVED PLASTIC PALLET SPRINKLER PROTECTIONIf a facility is storing a limited number of pallets, and the sprinkler system has not been designed for idle pallet storage, the most effective protection strategy is to store pallets no higher than 6 feet (1.8 m); and each pile of no more than four stacks should be separated from other pallet piles by at least 8 feet (1.4 m) of clear space or 25 feet (7.6 m) of commodity.

For larger quantities of pallets, the sprinkler design criteria in the following tables from NFPA 13 apply. Some insurers may have different design criteria.

Table 2 – Control Mode Sprinklers for Idle Wood Pallets

Height of Pallet Storageft. (m)

Max. Ceiling/Roof Height

Location ofStorage

Minimum Nominal Sprinkler K-Factor

Sprinkler Density

RequirementsArea of Sprinkler Demand ft2 (m2)

Temperature Rating

ft. (m) gpm/ ft2

(mm/min.)

286oF (141oC) 165o F (74oC)

Up to 6 (1.8)Up to 8 (2.4)8 (2.4) to 12 (3.7)12 (3.7) to 20 (6.1)Up to 20 (6.1)

20 30 30 30 30

(6.1)(9.1)(9.1)(9.1)(9.1)

On FloorOn FloorOn Floor/RacksOn Floor/RacksOn Floor

8 (115)11.2 (160)11.2 (160)

11.2 (160)

16.8 (240)

.20.45.60

.60

.60

(8.2)(18.3)(24.5)

(24.5)

(24.5)

2,0002,5003,500

4,500

N/A

(186)(232)(325)

(418)

3,0004,0006,000

N/A

2000

(279)(372)(557)

(186)

Table 3 – CMSA (Control Mode Specific Application) Sprinkler Protection for Idle Wood and UL Listed or FM Approved Plastic Pallets

Height of Pallet Storageft. (m)

Max. Ceiling/Roof Height

Location ofStorage

K-Factor/Orientation

Type of System

Number of Sprinklers

Design Pressure

ft. (m) Psi (bar)

Up to 20 (6.1) 30303030 303540

(9.1)(9.1)(9.1)(9.1)(9.1)

(10.6)(12.1)

On Floor

11.2 (160)/Upright11.2 (160)/Upright16.8 (240)/Upright16.8 (240)/Upright19.6 (280)/Pendent19.6 (280)/Pendent19.6 (280)/Pendent

WetDryWetDryWetWetWet

15251525151515

25 25 15 15 16 25 30

(1.7)(1.7)(1.0)(1.0)(1.1)(1.7)(2.1)

Willis North America | February 20144

Table 4 – ESFR (Early Suppression Fast Response) Sprinkler Protection for Idle Wood and UL Listed or FM Approved Plastic Pallets

Type of Sprinkler (orientation)

Location ofStorage

Nominal K-Factor

Maximum Storage Height

Maximum Roof/Ceiling Height

Design Pressure

Ft. (m) Ft. (m) Psi (bar)

ESFR (pendent)On floor or in racks without solid shelves

14.0(200)

25 (7.6) 30 (9.1) 50 (3.4)

25 (7.6) 32 (9.8) 60 (4.1)16.8(240)

25 (7.6) 30 (9.1) 35 (2.4)25 (7.6) 32 (9.8) 42 (2.9)35 (10.7) 40 (12.2) 52 (3.6)

22.4(320)

25 (7.6) 30 (9.1) 25 (1.7)30 (9.1) 35 (10.7) 35 (2.4)35 (10.7) 40 (12.2) 40 (2.8)

25.2(360)

25 (7.6) 30 (9.1) 15 (1.0)30 (9.1) 35 (10.7) 20 (1.4)35 (10.7) 40 (12.2) 25 (1.7)

ESFR (upright) On floor

14.0(200)

20 (6.1) 30 (9.1) 50 (3.4)20 (6.1) 35 (10.7) 75 (5.2)

16.8(240)

20 (6.1) 30 (9.1) 35 (2.4)20 (6.1) 35 (10.7) 52 (3.6)

PLASTIC PALLET SPRINKLER PROTECTIONTable 5 – ESFR (Early Suppression Fast Response) Sprinkler Protection for Idle Plastic Pallets

Type of Sprinkler (orientation)

Location ofStorage

Nominal K-Factor

Maximum Storage Height

Maximum Roof/Ceiling Height

Design Pressure

Ft. (m) Ft. (m) Psi (bar)

ESFR (pendent)On floor or in racks without solid shelves

K14.0(200)

25 (7.6) 30 (9.1) 50 (3.4)

25 (7.6) 32 (9.8) 60 (4.1)K16.8(240)

25 (7.6) 25 (7.6) 35 (2.4)25 (7.6) 32 (9.8) 42 (2.9)35 (10.7) 40 (12.2) 52 (3.6)

If plastic pallets are not protected by ESFR sprinklers, they should be protected by one of the following:

1. When plastic pallets are stored in a cut-off room:

� The cut-off rooms shall have at least one exterior wall.

� The plastic pallet storage shall be separated from the remainder of the building by 3-hour rated fire walls.

� The storage shall be protected by sprinklers designed to deliver 0.6 gpm/ft2 (24.5 mm/min) for the entire room, or high-expansion foam and sprinklers designed to deliver 0.30 gpm/ft2 (12.2 mm/min) for the entire room.

� Storage shall be piled no higher than 12 feet (3.7 m).

� Steel columns shall be protected by 1-hour fire proofing, or a sidewall sprinkler directed to one side of the column at the top or at the 15 feet (4.6 m) level, whichever is lower.

2. Where plastic pallets are stored without cut-offs from other storage:

� Maximum storage height shall be 10 feet (3.05 m).

� Maximum ceiling height shall be 30 feet (9.1 m).

� Sprinkler density shall be 0.6 gpm/ft2 over 2000 ft2 (24.4 mm/min over 186 m2).

� Minimum sprinkler shall have K-factor of 16.8 (240).

3. Plastic pallets shall have no impact on the required sprinkler protection when stored as follows:

� Storage no higher than 4 feet (1.2 m).

� High-temperature rated sprinklers used.

� Each pallet pile of no more than two stacks to be separated from other pallet piles by at least 8 feet (2.4 m) of clear space or 25 feet (7.6 m) of stored commodity.

� Minimum ordinary hazard, Group 2 sprinkler design.

Resource: Tables 1-5, NFPA 13: Standard for the Installation of Sprinkler Systems

For additional information on the hazards of idle pallet storage, contact your Willis Client Advocate®, your Willis Property Risk Control consultant or:

John Ammeson, PE, ARM, CFPSSenior Property Risk Control ConsultantRisk Control and Claim Advocacy Practicejohn.ammeson@willis.com

Willis North America Inc.

Brookfield Place200 Liberty Street7th Floor, New YorkNew York 10281-1003United StatesTel: +1 212 915 8888

www.willis.com

The observations, comments and suggestions we have made in this publication are advisory and are not intended nor should they be taken as legal advice. Please contact your own legal adviser for an analysis of your specific facts and circumstances.

50209/02/14