Aug 2014

Fire Safety Systems for Industrial Occupancies

Recent studies by Liberty Mutual and National Fire Protection Agency (NFPA) have shown that sprinklers are the most effective way to reduce loss of life and property damage in industrial occupancies (warehouses and manufacturing facilities). This should come as no surprise. These studies are by NFPA and the National Fire Incident Reporting System (NFIRS), which is a United States federal department that obtains data that can be used to more accurately assess and consequently combat fire issues on a national level.

A NFPA study revealed that of the all the industrial fires from 2007-2011, 32% of warehouses had some type of sprinkler system present and 48% of manufacturing facilities had a sprinkler system present. Overall sprinklers operated in 91% of fires with sprinkler systems without failure. Nearly 2/3 of the reasons for sprinkler failure was due to system shut off.

There are two main types of sprinkler systems, wet pipe and dry pipe. For the study in manufacturing facilities that have a sprinkler system, 85% were wet pipes and 12% were dry pipes. The numbers are similar in warehouses with 79% being wet pipe and 20% were dry pipe. It should be noted that cold storage is excluded from data of warehouses. (FYI: Wet pipe sprinklers have water in the pipe system that is released immediately when heat from the fire causes the water to discharge. Dry pipe sprinkler systems contain oxygen or nitrogen in the pipe system that under pressure is released, which allows the water pressure to open valve and release water.) Dry pipe systems that are operating are less likely to open one sprinkler than wet pipe systems. This is a due to a time delay that allows the fire to spread. The delay is because the dry pipe valve has to operate and the water has to pass through the piping to the open sprinkler. Therefore once the fire has spread it is more likely to open more dry pipe sprinklers. Effectiveness of a sprinkler system falls every time another sprinkler is opened.

Sprinkler Effectiveness Related to Number of Sprinklers Operating

2007-2011 Structure Fires*

Number of Sprinklers OperatingAll SprinklersAll StructuresManufacturing FacilitiesWarehouse (Excluding cold Storage)
3 to 593%93%94%96%
6 to 1080%80%87%96%
more than 1085%85%96%79%

(*Data taken from June 2013 NFPA Journal, US Experience with Sprinklers)

Wet pipe systems, the more popular system, controlled 84% of warehouse fires and 86% of manufacturing facilities fires. Also in manufacturing facilities property damage was 38% lower and deaths per thousand was 88% lower when wet pipe sprinklers were present compared with buildings with no automatic extinguishing systems. (*Data Obtained from June 2013 NFPA Journal, US Experience with Sprinklers) In warehouses with wet pipe sprinklers death per thousand was 61% lower when compared to warehouses with no automatic extinguishing equipment was present. In industrial occupancies deaths are rare, so the studies go by deaths per thousands. There are rare fatal fires in industrial occupancies. Sprinkler systems are designed to confine the fire in the room of origin thereby reducing damage to surrounding area, therefore effectiveness should be measured relative to the design and intention of the sprinkler system. These studies conclude that wet pipe sprinklers are the most effective system to protect assets and employees in industrial occupancies.

Number of Sprinklers Operating that Control the Fire

Number of Sprinklers OperatingWet PipeDry PipeOther type of SprinklerAll Sprinklers
2 or fewer88%73%64%86%
3 or fewer92%%80%72%91%
4 or fewer94%85%79%93%

By Type of Sprinkler System

(*Data taken from June 2013 NFPA Journal, US Experience with Sprinklers) Reasons why sprinklers may be ineffective include not enough water, fire is inappropriate for systems (explosions, flash fires), lack of maintenance, system shut off, or water did not reach the fire. It is important to note the difference between human error and mechanical error. Human error does not affect sprinkler systems alone but may have the same amount of damage to every fire safety system. These studies do not include fires not controlled by operational sprinkler system, therefore it is not including buildings under construction, fires too small to cause the sprinkler to react, or fires being confined to cooking equipment or commercial compactor.

A sprinkler system may be installed in your facility but is it designed and maintained properly? Risk Logic can help with your automatic sprinkler system design.