Last week, we started to scratch the surface of fire hazards in cold storage warehouses. This week, we’ll look at a few more unique fire hazard challenges, as well as two loss examples that highlight the unique challenges found in such facilities. 

More Unique Hazards in Cold Storage Warehouses


Fighting a fire inside of a refrigerated/freezer space can be extremely difficult as the insulated walls and ceiling will retain the heat and smoke within the space. The fire department will have difficulty venting the heat and smoke, resulting in zero visibility. In industries particularly sensitive to smoke and contamination, such as food, even a small fire can cause a large monetary loss, due to smoke contamination.

Ice Plugs

Freezing temperatures make the use of wet pipe sprinkler systems impractical for coolers and freezers so double-interlock pre-action sprinkler systems are often utilized, but reliability concerns remain.

Moisture, if present in the air, will condense and accumulate in the interior of the piping, which can form an ice plug. Ice plugs are often found in the feed main inside the freezer, where the pipe enters the freezer and beyond, up to a distance of 10 to 15 ft.

To prevent the formation of ice plugs, a listed air compressor with an air dryer, or a source of compressed nitrogen, should be used as the air supply for a pre-action system protecting a refrigerated space.

To prevent the possibility of trapped water in the piping, ensure piping is properly pitched. Pipe pitch should be at least 1⁄2 in. for every 10 ft in branch lines, cross and feed mains, and piping in rack sprinkler systems.

Preaction sprinkler protection

Double- Interlock Pre-action sprinkler systems are often used in coolers and freezers. These systems have a detection system, such as linear heat detection cable at the roof, and also have supervisory air in the system to detect when a sprinkler has activated. Double interlock pre-action systems require a detection signal AND an open sprinkler that releases the supervisory air, before the deluge valve will allow water to flow into the piping. This prevents accidental flow of water into the piping, which would quickly freeze within the freezer space.

These systems are more complex than a typical wet pipe sprinkler system and therefore more prone to failure unless properly inspected, tested, and maintained according to the requirements in NFPA 25.

Quell systems

To address some of the concerns about reliability, Tyco introduced the Tyco QuellTM Fire Sprinkler System.  The system was developed using the concept of performance-based design under the equivalency paragraph in NFPA 13.  The Quell system delays water delivery until an appropriate number of Control-Mode Special Application (CMSA) sprinklers have operated so that an optimum number of sprinklers are discharging onto the fire and pre-wetting the surrounding storage. The Quell system utilizes:

  • Tyco QRS electronic accelerator
  • Tyco Ultra K17, 286 Deg F, CMSA sprinklers
  • Tyco SprinkFDT QTM dry pipe system water delivery software
  • Potter 4410 RC control panel
  • SAFE Fire Detection Inc. ThermoCable® line-type heat detection

Loss Examples

The National Fire Protection Association (NFPA) released a report in March 2011, which reviewed several cold storage facility loss examples. Two of those incidents really highlight the unique fire hazards cold storage facilities present:

Exposed Polyurethane Insulation, Washington

The 200,000-square-foot apple packing and storage complex consisted of three separate buildings. The building of origin was subdivided into about seven controlled-atmosphere cold storage rooms. This building had corrugated-steel walls and roof on a steel frame. The room of origin was insulated with two layers of foam plastic material. The first layer was polystyrene block and the exterior layer consisted of 2 1/1 to 3 inches of sprayed-on polyurethane. There was no thermal barrier protecting the foam insulation.  The buildings were not protected by an automatic sprinkler system, nor did they have an automatic fire detection system. The facility’s fire-extinguishing equipment was limited to several portable fire extinguishers in each section and two yard fire hydrants supplied by the district irrigation system.

At approximately 11:10 am, two workmen were cutting a hole in a steel truss near the ceiling of the cold storage room with a cutting torch. The polyurethane insulation ignited, and the workmen attempted to extinguish the fire using a small carbon dioxide extinguisher. The extinguisher was quickly emptied, and had no apparent effect on the fire. The men left to get an additional 40-lb. dry chemical extinguisher, but by the time they returned, the fire had spread across the ceiling of the room and had heavy black smoke forced them to abandon their efforts.

The fire knocked the telephones out of service, which further delayed transmission of the alarm to the fire department. The fire department received the first alarm at 11:24AM and promptly responded. Arriving firefighters found two sections of the complex almost totally involved in the fire and were able to extinguish the fire in about two hours.

The rapid flame spread over the unprotected polyurethane insulation and the lack of fire protection and extinguishment equipment were key factors contributing to this estimated $2,500,000 loss.

Reference:  Fire Analysis and Research, 1977, “Bimonthly Fire Record”, Fire Journal, September, 45.

Ammonia Explosion, Mississippi

Leaking ammonia, ignited by a gas-fired unit heater, exploded at this milk-processing, ice-cream manufacturing plant.

The explosion occurred in a one-story packaging warehouse. The building was constructed of concrete blocks with a roof system of cement fiberboard on steel joists and steel columns. There was no automatic sprinkler protection.

At approximately 7:05AM, the plant superintendent noticed that the high-pressure compressor to the freezers was not operating. At 7:10AM, he returned to the compressor room with a maintenance man. They observed that the pressure gauge on the intermediate cooling system was reading in excess of 150 psi. They could also hear gas escaping in the adjoining warehouse area. The two men immediately began to shut down electrical equipment and notified plant employees to evacuate the building. At approximately 7:15AM, the escaping ammonia exploded. Because the explosion damaged telephone lines, a maintenance man was sent across the street to phone the fire department.

Firefighters ventilated the roof and extinguished the fire using four large hand lines. There were no reported injuries to plant personnel or firefighters.

Investigation revealed that a pressure switch failed in the intermediate cooling system. This caused a relief valve on a coil-jacketed tank to open, leaking gas into the warehouse area. This valve was not vented to the outdoors or back into t lower-pressure section of the system. The ceiling-hung gas unit heaters provided ignition.

Loss to the structure and building contents was estimated at $200,000.

Reference: Fire Analysis and Research, 1979, “Bimonthly Fire Record”, Fire Journal, September, 13.


Cold storage warehouses are in a category of their own. They have all the typical exposures found in any warehouse, as well as many hazards and challenges that are unique to refrigerated warehouses. These challenges can be managed with awareness of the special hazards introduced by insulation and refrigeration, and the need for special sprinkler protection systems that are appropriate for protection of refrigerated spaces.

If you need assistance developing a fire protection solution for your cold storage warehouse, think about seeking the expertise of a fire protection engineer, like the ones at Harrington Group, Inc. Give us a call today, or fill out the form below. [gravityform id=”1″ name=”Contact Us”]