The Dangers of Battling Fires Involving Oxidizers: A Case Study

BY JEFFREY A. HARWELL

Whenever firefighters respond to a reported structure fire in a sprinklered building, they usually feel confident they will be facing a rather small incident, and the data support their assumption. But for the second time in the same year, the Dallas/Ft. Worth, Texas, area experienced another large loss fire in a fully sprinklered warehouse.1 The most recent fire took place in a Dallas warehouse whose primary tenant was a pool supply company. The first-due engine to this most recent fire radioed for a second alarm while still en route because of the large column of smoke visible in the distance—a clear indication that something had gone wrong. This particular fire should serve as a reminder of the dangers posed by the storage of oxidizers and the rapid, explosive rate at which they can burn.

(1) The fire scene looking north from the south end of the warehouse along Dan Morton Drive.
(1) The fire scene looking north from the south end of the warehouse along Dan Morton Drive. The ladders of Trucks 15, 26, and 49 are raised. Trucks 26 and 49 are already flowing water. [Photo courtesy of Dallas (TX) Fire-Rescue.]

CONSTRUCTION ASPECTS OF THE WAREHOUSE

The fire building was situated in an industrial area in the far southwest corner of Dallas near the border with the city of Duncanville. Construction of the warehouse was completed in 1980. It measured 1,009 feet by 225 feet and consisted of concrete tilt walls with a tar-and-gravel roof on a metal roof deck supported by a series of steel beams, steel bar joists, and steel columns. The roof was 28½ feet above the finished floor.

At the time of the fire, the main tenant was a pool supply company that occupied roughly the north half of the warehouse. The space served as a distribution center for the company’s retail stores in the Dallas/Ft. Worth area and housed a full line of equipment and chemical supplies for swimming pools and spas. A food bank operation had just leased the southern half of the warehouse and had moved only a limited amount of equipment into its space at the time of the fire.

Overhead doors lined the majority of the west exterior wall of the warehouse. Each overhead door had a large number printed on a sign above it. The numbering system appeared to be based on two original tenants occupying the warehouse roughly equally, with doors along the north half numbered 1 to 23 from north to south and doors along the south half numbered 1 to 28 from south to north (Figure 1). An abandoned railroad spur ran alongside the entire east exterior wall; there was no vehicular access to this side.

Figure 1. Apparatus Placement at 1430 Hours August 13, 2011
(1) The fire scene looking north from the south end of the warehouse along Dan Morton Drive.
(1) The fire scene looking north from the south end of the warehouse along Dan Morton Drive. The ladders of Trucks 15, 26, and 49 are raised. Trucks 26 and 49 are already flowing water. [Photo courtesy of Dallas (TX) Fire-Rescue.]

OXIDIZER STORAGE ROOMS

The pool supply company moved into the warehouse in late 1990, and its 100,800-square-foot space was denoted as Suite 100. A two-hour fire-rated area separation wall divided Suite 100 from Suite 103 to the south. There were no openings in this wall.

When plans were submitted for the pool company lease space, they included three new rooms—two oxidizer storage rooms and a flammable liquids storage room at the northeast corner of the space. The Building Department reviewed the plans and required fire-rated walls for the rooms. The Class 3 storage room was 4,500 square feet and was required to have four-hour rated walls. The Class 1 and 2 oxidizer storage room was 6,100 square feet and was required to have one-hour rated walls. The 550-square-foot flammable liquid storage room was required to have two-hour rated walls.

At the time of the fire, the flammable liquid storage room had become a Class 2 oxidizer storage room housing bromo chloro dimethyl hydantoin. The Class 1 and 2 oxidizer storage room was storing only two types of Class 1 oxidizers—sodium dichloride and sodium trichloride. The Class 3 oxidizer storage room remained unchanged, housing calcium hypochlorite.

At some point, the pool supply company gained an additional 25,425 square feet by leasing Suite 103. To provide access to the new space, a new door was apparently added in the two-hour area separation wall that was large enough to drive a forklift through. It’s unknown whether this new door was fire rated.

FIRE PROTECTION FEATURES

The water supply for the automatic sprinkler system was fed from an underground main located along Dan Morton Drive. The piping from the city main split on the west side of the warehouse, with one line serving the north riser room and one line serving the south riser room. There were two post-indicating valves, one on either side of the split. These aboveground control valves allowed the automatic sprinkler system for the north half, the south half, or the entire warehouse to be shut down without having to enter one of the riser rooms. At the time of the fire, neither of these valves was clearly visible because of various materials and trailers stored in the yard. The exact number of automatic sprinkler risers in each riser room was unknown.

Detailed information concerning the fire alarm system was also not available; however, it’s believed the system monitored only waterflow and tamper switches.

The original sprinkler plans and calculations for the building revisions coinciding with the 1990 remodel to accommodate the pool supply company could not be located, but the fire department files did include a copy of the plan review comments. From these comments, the storage method for the two oxidizer storage rooms was as follows: Material in the Class 1 and 2 oxidizer storage rooms was stored in racks to a height of 19 feet, 6 inches; material in the Class 3 oxidizer storage room was stored in racks to a height of 16 feet. Both rooms featured in-rack automatic sprinklers initially. The sprinkler density for the Class 3 oxidizer storage room was believed to be 0.51 gallons per minute (gpm) per square foot over the most remote 2,300 square feet.

In 2005, the racks were removed from the Class 3 oxidizer storage room, and all items were stored in a palletized storage arrangement on the floor. At that time, the in-rack sprinklers were also removed. There were no other known changes to the sprinkler system.

CODE DEVIATIONS

There were two important deviations from the fire code noted in the 1990 automatic sprinkler plan review comments. The first involved fire department access. Since the entire east side of the warehouse had the abandoned railroad spur and was not accessible by fire apparatus, it did not meet local fire code requirements. This deficiency was waived based on the fact the entire building was equipped with an automatic sprinkler system.

The second issue involved water supplies. There was enough water available to meet the automatic sprinkler system demand, but there was not enough water to meet the fire flow requirements found in the local fire code. This deficiency was also waived using the same reasoning—the warehouse was equipped throughout with an automatic sprinkler system.

EVENTS PRIOR TO FIRE DEPARTMENT ARRIVAL

On the morning of the fire, a lone employee of the pool supply company was working in the office section at the northwest corner of the building. The employee recalled hearing crackling noises, soon followed by a loud boom sound, similar to thunder. The employee left his office and entered the office hallway, where he noticed a strong rush of air coming from behind him (from the direction of the oxidizer storage rooms). The draft was strong enough that it opened the exterior door before he could reach it.

After a quick survey of conditions on the outside of the building, he went back through the office space and entered the warehouse area. At first, everything appeared to be normal. Then, dark smoke began rapidly pouring from the area of the oxidizer storage rooms into the warehouse and over the space above the offices. The employee quickly went back through the offices to exit the structure and call the fire department. Shortly after exiting the structure, he heard a loud thud sound, which turned out to be a tilt wall panel along the north side of the warehouse crashing into the break room (photo 2).

(2) This view of the north exterior wall shows the one missing wall panel that was sucked into the building before the fire department arrived.
(2) This view of the north exterior wall shows the one missing wall panel that was sucked into the building before the fire department arrived. Most of the other wall panels are leaning outward and are in danger of collapsing. (Photo by author.)

At 10:10 a.m. on August 13, 2011, the Dallas fire communication office received the cell phone call from the employee reporting the structure fire at 4202 Dan Morton Drive. At the exact same time, the monitoring service was receiving a waterflow alarm from the warehouse. A first-alarm assignment consisting of Engines (E) 52, 49, and 40; Truck (T) 49; and Battalion Chiefs (BC) 6 and 5 was dispatched. A short time later, E-52 radioed communications it was en route and had heavy grayish-white smoke billowing into the sky from the reported address. It also asked for the second alarm to be transmitted even though it was not on scene yet. Based on the expected contents of the pool supply warehouse, it also requested a hazardous materials box be transmitted.

At 10:13 a.m., T-26 and Rescue (R) 52 were dispatched as part of the working fire assignment. The second alarm was dispatched at 10:14 a.m. and consisted of E-26, E-36, and E-33; T-15 and T-25; BCs 1 and 9; and Deputy Chief (DC) 807. This was followed six minutes later by the dispatch of E-3 and Hazmat 3 as part of the hazardous materials box. There were now seven engines, four trucks, and four BCs responding to the fire with the first-due unit just arriving on the scene.

FIRST-ARRIVING UNITS

The initial size-up by first-arriving E-52 indicated operations would be totally defensive because of the heavy fire involvement at the north end of the warehouse. By this time, the smoke had turned to a dark black color. Based on the presence of tilt-wall construction, aerial operations were immediately set up to provide better stream penetration into the heart of the fire. This tactic also allowed personnel to remain outside of the collapse zone created by the likely collapse of the tilt walls.

T-49 was the first aerial to arrive and set up operations on the west side of the warehouse in the vicinity of Door #10, which was approximately 150 feet from the north end of the warehouse. T-26 was the second aerial to arrive and set up approximately 150 feet to the south of T-49 near Door #20. T-25 was the third-due aerial and set up on the north side of the warehouse. All apparatus were positioned based on the possible outward collapse of the tilt walls.

DC-807 arrived on the scene at 10:29 a.m. and noted heavy fire involvement extending from the north exterior wall all the way down to Door #17. Within this involvement area, approximately one-fourth of the roof had already collapsed and several wall panels were starting to lean outward. One minute after the arrival of the deputy chief, a third alarm was transmitted, bringing E-23, E-47, and E-46 as well as T-23 to the scene.

Shortly thereafter, E-15, T-15 and T-19, USAR-19, and Battalion 3 were added to the assignment. Based on the expected progression of the fire in a southward direction, T-15 and T-19 were positioned approximately at the midpoint of the warehouse. When T-23 arrived, it set up its aerial 100 feet south of T-15. By the time third-alarm companies began setting up, the progressing flame front was already approaching the fire-rated wall separating Suites 100 and 103 (photo 3).

(3) In this photo, taken as the third-alarm companies were arriving, T-26 is operating its aerial stream in the vicinity of Door #20.
(3) In this photo, taken as the third-alarm companies were arriving, T-26 is operating its aerial stream in the vicinity of Door #20. If you look at the top of Door #23, fire is already starting to impinge on the overhead door. The wall where firefighters made their stand is behind the truck cab. The fire traveled around 440 feet through the warehouse in only 28 minutes. [Photo courtesy of Dallas (TX) Fire-Rescue.]

The fourth alarm was transmitted at 10:37 a.m. It brought E-16, E-14, and E-25 and T-36 to the fire. When E-14 arrived on scene, it was directed to catch a hydrant on West Ledbetter Street and supply the fire department connection (FDC) on the west side of the warehouse. Although the automatic sprinkler systems at the north end of the warehouse appeared to be damaged and nonfunctional, the fire was moving southward into exposure areas and command wanted to boost pressure for any of these sprinklers that might be operating (photo 4).

(4) Command personnel must remember that if there's any chance the sprinkler system is helping to control the spreading fire, the FDC must be charged as quickly as possible.
(4) Command personnel must remember that if there’s any chance the sprinkler system is helping to control the spreading fire, the FDC must be charged as quickly as possible. At this fire, Engine 14 (pictured) used its entire hosebed to lay in from a hydrant on West Ledbetter Street to supply the FDC (just to the left of the fire hydrant). (Photo by author.)

As previously mentioned, the east side of the warehouse featured an abandoned railroad spur and was inaccessible for fire apparatus. Immediately beyond the railroad spur, there was a large area of brush. Because of the long dry summer in north Texas, command became concerned about the fire spreading into the brush and creating an additional logistics issue. At 10:40 a.m., command special called two brush trucks to handle any fire extension that might spread into the brush. On the morning of the fire, a brief thundershower had provided enough rain to prevent a significant brush fire.

STRATEGY

The fire was moving from north to south in a building that was 1,000 feet long, so the most pressing objective was to find a suitable cutoff point to halt the fire spread. Early on, firefighters attempted to make entry at Door #17, but they quickly abandoned this position because of the fire’s rapid progression across the ceiling (photo 5).

(5) This was the first location in which firefighters attempted to cut off the spreading fire near Door #17.
(5) This was the first location in which firefighters attempted to cut off the spreading fire near Door #17. The location was quickly abandoned. (Photo by author.)

The next location chosen was a concrete block wall situated between Door #23 and Door #28. This was the original two-hour fire-rated area separation wall between Suite 100 and Suite 103. The biggest issue with this location involved the forklift door, so several handlines were stretched to protect this opening. A BC was assigned as a safety officer to monitor conditions in this area; he was instructed to immediately evacuate crews at the first sign of any form of structural integrity issues. To aid these firefighters, a large trailer-mounted fan was placed adjacent to one of the overhead doors to pressurize the exposure space in which the firefighters were operating (photo 6).

(6) A truck-mounted fan was used to pressurize the exposure space.
(6) A truck-mounted fan (bottom of photo) was used to pressurize the exposure space. (Photo by author.)

The fifth and final alarm was transmitted at 11:14 a.m. and brought E-45, E-38, and E-24 to the scene. Because of the water supply problems the companies were experiencing on the fireground, command designated one of the multiple-alarm companies as the water resource company. This company was assigned to map out all available hydrants in the area so command could determine if any additional water sources would be available if the fire continued to spread.

The toxicity of the smoke was a concern from the beginning. However, by the time air-quality testing was initiated, no abnormal readings were obtained. Agencies tested the water runoff from the fire building; again, there were no abnormal readings.

As the incident progressed, firefighters were able to maintain their position at the area separation wall between Door #23 and Door #28. Handlines protected the forklift opening as well as an opening that formed when a portion of the wall collapsed near the east exterior wall.

Once ventilation efforts started to become effective, firefighters operating in the exposure space made an interesting discovery (ventilation was accomplished by using the previously mentioned truck-mounted fan to pressurize the space in conjunction with taking out skylights). As the smoke began to clear, firefighters noticed that a sizable portion of the concrete block wall behind them had collapsed. This would have been the wall separating Suite 103 from Suite 106. Although there was no fire damage in the immediate vicinity of this wall, firefighters believe the collapse was attributed to the distortion of the steel beams that ran through the wall.

The fire started darkening down around 1:00 p.m. Some multiple alarm units began to clear the scene while other companies throughout the city started rotating to the scene for overhaul duty. Two firefighters were transported to area hospitals with heat-related injuries (the temperature at the time of the fire was 80°F with a dew point of 74°F). The loss was estimated to be just over $9 million.

FIRE LOSS INVOLVING OXIDIZERS

Oxidizers are classified using a four-tier system, with Class 1 being the least hazardous and Class 4 the most hazardous. The storage method for oxidizers is a critical factor in preventing fires. Allowing incompatible materials to interact with oxidizers is a common cause of ignition. Even water in small amounts can cause a reaction when mixed with oxidizers. If large amounts of incompatible materials are allowed to interact with any class of oxidizers, an explosive reaction can occur. Oxidizers are even susceptible to damage during transport. If a pallet load of oxidizers becomes damaged, there is a strong chance the load will become unstable and eventually result in ignition. For the fire service, putting water on oxidizers complicates matters even more, as the water will cause the release of chlorine. Many times, firefighters think a fire involving oxidizers has been extinguished, and it flares up moments later.

There have been a number of noteworthy fires involving the storage of oxidizers used for swimming pools. Information on three of these fires can be found in investigative reports issued by the National Fire Protection Association (NFPA) as well as Factory Mutual Insurance data sheets. Two of these fires involved bulk retail home improvement stores (Quincy, Massachusetts, on May 23, 1995, and Albany, Georgia, on April 16, 1996) that sold oxidizers along with a wide range of other items. In both cases, the fires originated in the area where pool chemicals were stored, and it quickly spread.

The Quincy store featured an automatic sprinkler system that had been designed to deliver 0.6 gallons per minute per square foot over the most remote 2,000 square feet. The fire was started by motor oil leaking onto the oxidizers. The fast-moving fire eventually opened 22 sprinkler heads and required significant manual firefighting efforts to achieve final extinguishment. The estimated loss was $5 million.

The Albany store featured an automatic sprinkler system designed to deliver 0.33 gpm per square foot over the most remote 3,000 square feet. A fire of undetermined origin quickly overwhelmed the sprinkler system, causing an estimated $10 million in damages. Neither store featured in-rack automatic sprinklers.

The NFPA investigation into an August 2, 2000, fire in a Phoenix, Arizona, home and garden warehouse found similarities with the Dallas fire. A fire starting in the oxidizer storage area of the warehouse had progressed to the extent that the first-arriving companies could not conduct an interior attack. Firefighting operations were concentrated on protecting exposures; this task was complicated by the toxic characteristics of the smoke being produced by the fire. A concrete wall between the home and the garden warehouse and an attached pharmaceutical warehouse became compromised, allowing the fire to spread. In the end, both warehouses were completely destroyed; losses were estimated at $101 million. Once again, inadequate storage arrangements for oxidizers and inadequate sprinkler protection were listed as contributing factors. The ceiling sprinkler system had been designed to deliver 0.495 gpm per square foot over the most remote 2,000 square feet; there were no in-rack sprinklers.

Another fire in a Conyers, Georgia, manufacturing facility for pool and spa chemicals on May 25, 2004, has received less publicity. A fire of undetermined origin started in the warehouse portion of the facility that included Class 3 oxidizers and eventually overwhelmed the automatic sprinkler system. Officials were aware of inadequate storage arrangements for oxidizers, as well as inadequate sprinkler densities, prior to the fire and were in the process of implementing needed changes. Firefighters battled the fire for two days; mandatory evacuations were needed because of the toxic smoke being produced.

DALLAS FIRE INVESTIGATION

The investigation into the most recent Dallas fire by Dallas Fire-Rescue and the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) listed the cause of the August 13, 2011, fire to be of undetermined origin. There is no doubt the fire started in the Class 3 oxidizer storage room. There were three likely scenarios that could have led to ignition.

Ventilation was noted as a key problem in the storage rooms. Limited ventilation allowed for extreme variations in temperature. Based on information obtained from the Phoenix (AZ) Fire Department following its fire, investigators learned the maximum recommended temperature for a room containing oxidizers was 85°F. What little air movement there was inside the room was provided by a fan that was drawing outside air into the room. In the days leading up to the fire, the Dallas area was experiencing record-breaking high temperatures. Thus, the temperature inside the room on a typical summer day was estimated to be 20°F to 30°F over the maximum recommended temperature on a routine summer day, which could have caused the oxidizers to become unstable.

Although general housekeeping in the room was considered to be good, employees noted a constant problem with rust forming at the ceiling of the room and then dropping down onto the product. This would have introduced an incompatible material among the oxidizers that could have led to ignition.

The third scenario involved a possible water leak at the ceiling level. Employees reported this had been an issue in the past, and on the morning of the fire a brief thunderstorm moved through the area. Any water entering the room would have provided the incompatible material that could have been the catalyst for ignition.

When ignition did occur, an explosive reaction took place, and the entire oxidizer storage area became completely engulfed by fire, which produced the copious amounts of grayish smoke observed by first-arriving companies. As the oxidizers became completely incinerated by the rapidly moving fire, the smoke color changed to black as the fire moved southward through the remainder of the warehouse. This would explain why there were no air-quality issues by the time testing was initiated—all of the chemicals had been consumed in the first few minutes of the fire.

EFFECTIVENESS OF THE AUTOMATIC SPRINKLERS

We in the fire service should be alarmed by one particular fact at this point: The warehouse, along with the oxidizer storage rooms, was thought to be equipped with a fully functional, code-compliant, automatic sprinkler system. Yet, the system amazingly did little to slow down the rapid progression of the flame front. The alarm company’s receiving the water flow alarm at the exact same time as the employee was reporting the fire indicates there was no delay in the operating of the automatic sprinkler system.

Taking the racks and associated in-rack sprinklers out of the Class 3 oxidizer storage rooms should have triggered a reevaluation of the sprinkler requirements for the room. The removal of the in-rack sprinklers meant the ceiling sprinkler densities had to be increased to deliver higher amounts of water to make up the difference. Instead of delivering 0.51 gpm per square foot over the most remote 2,300 square feet, the ceiling sprinklers should have been delivering a minimum of 0.65 gpm per square foot over the most remote 5,000 square feet. These densities are based on the 2004 edition of NFPA 430, Code for the Storage of Liquid and Solid Oxidizers. In other words, the ceiling system was delivering only 1,700 gpm when it should have been delivering at least 3,750 gpm.

These minimum flow rates were calculated by multiplying the water density by the expected fire size (i.e., the needed flow based on NFPA 430 was 0.65 gpm/square foot × 5,000 square feet = 3,250 gpm + 500 gpm for hose streams). Each sprinkler head in the storage room covered an area of 100 square feet, which meant each head should have been delivering a minimum of 65 gpm (0.65 gpm/square foot × 100 square feet).

In comparison, a light hazard office occupancy would have a minimum flow rate of 250 gpm (0.1 gpm/square foot × 1,500 square foot + 100 gpm for hose streams) and each sprinkler head would be delivering a minimum of 22.5 gpm (0.1 gpm per square foot × 225 square feet).

One of the unique findings to come out of this fire involved the Class 1 oxidizer storage room. This room shared a wall with the Class 3 storage room, where the fire and explosion originated. Yet, a sizable portion of the products in this room received minimal fire damage. In addition, the roof above this room remained relatively intact while all of the surrounding roof had collapsed (photos 7 and 8).

(7) The fire/explosion started in the Class 3 oxidizer storage room at the far left of the photo, moved around the Class 1 oxidizer storage room at the center, and quickly moved to the rest of the warehouse at the far right.
(7) The fire/explosion started in the Class 3 oxidizer storage room at the far left of the photo, moved around the Class 1 oxidizer storage room at the center, and quickly moved to the rest of the warehouse at the far right. Investigators credit the minimal damage in the Class 1 oxidizer storage room to the operation of the in-rack sprinklers. Visible across the top of the photo is the large area of exposed brush that resulted in the special call of two brush trucks. (Photo courtesy of Dallas Fire-Rescue/ATF.)
(8) This photo zooms into the Class 1 oxidizer storage room from the same vantage point as photo 7.
(8) This photo zooms into the Class 1 oxidizer storage room from the same vantage point as photo 7. The photo clearly demonstrates how well the sprinklers—in particular the in-rack sprinklers—protected the product. (Photo courtesy of Dallas Fire-Rescue/ATF.)

Investigators attribute this condition to the operation of the in-rack automatic sprinklers. In a number of other fire investigations, including those involving oxidizers, the installation of in-rack automatic sprinklers was listed as part of the recommendations to reduce the size and severity of future fires. The results observed in this most recent Dallas fire did nothing to disprove this recommendation.

CONSTRUCTION FEATURES, STORAGE CONFIGURATION

One construction feature aided the rapid fire progression from the Class 3 oxidizer storage room into the remainder of the warehouse. Per requirements from the Building Department, the walls of the Class 3 oxidizer storage room were supposed to carry a four-hour fire rating. Following the fire, investigators estimated these walls to be well below the four-hour rating; they consisted of only two to three layers of gypsum wallboard at best. Very little of the wall remained following the fire. When the explosive reaction occurred in the room, the flame front faced little resistance as it rapidly moved out into the warehouse areas. The pressure differential was so great that one of the tilt-wall panels on the north exterior wall was sucked into the building and collapsed onto the break room. This event also likely damaged a significant portion of the sprinkler piping in the area.

Since the Class 3 oxidizer storage room was totally destroyed, the actual storage height of products in the room could not be determined. The pool company reported the height to be less than 12 feet, but investigators believe the actual height was at least 12 feet. The original approved storage height was 16 feet above the finished floor based on the product being stored on racks. There is no documentation in the records to indicate this maximum storage height was modified when the racks were removed and the storage method was changed to palletized storage on the floor.

The fire code that would have taken effect soon after the warehouse was constructed would have reduced the maximum storage height to 10 feet. The current edition of NFPA 430 also limits the storage height to 10 feet and even reduces it to five feet depending on the sprinkler density and the amount of product being stored.

This fire, along with other previously mentioned fires involving oxidizers, shows the importance of good housekeeping and strict adherence to fire prevention standards to keep ignition from occurring because once ignition does occur, things go downhill in a hurry. Most jurisdictions will want to take a closer look at existing structures that house oxidizers. Officials will have to determine if previous codes governing the storage of oxidizers are still adequate and retroactively enforce new standards as needed. In some jurisdictions, the hazardous materials portion of the fire code may be the only part that is already retroactive. Most importantly, don’t pass an ordinance unless you are ready to enforce it with minimal yearly inspections by a qualified inspector.

The most frightening aspect of this incident for the fire service involves the scenario of fire department units arriving before the explosion to investigate a report of smoke conditions in the warehouse. Had firefighters been searching for the source of the smoke when the explosion took place, they would have had only minutes to safely exit the structure. In a large warehouse with an endless number of aisles and passageways, a rapid escape is not always possible. The tilt-wall panel collapsing onto the break room during the first two minutes following the explosion posed an additional life-threatening danger to firefighters.

LESSONS LEARNED AND REINFORCED

  • For larger buildings, find ways to help establish common reference points to aid in communicating orders. In this incident, since the building was 1,009 feet long, the number signs above each overhead door gave firefighters a common reference point to use for all communications. This information should also be contained in the prefire plan.
  • The same reference points mentioned above can be useful in outlining sprinkler zone coverage areas in the prefire plan. This will allow command to determine which sprinkler zones have become ineffective because of fire progression and building collapse so they may be shut down to conserve water. In an incident such as this, conserving water was a significant issue since the available fire flow was already limited. Any extra water was needed for master stream devices protecting exposures. The extra water was also needed to ensure adequate water was still available to supply sprinklers that might be operating in any exposure areas. Note outside post indicating valves and valves at the connection to the city water main on the prefire plan because, as this fire showed, the post indicating valves may not always be visible on the fireground.
  • Based on a comment in the automatic sprinkler review notes, inadequate water was available for fire flow requirements contained in the fire code. According to these notes, the minimum fire flow requirements for this warehouse were waived based on the fact that the entire warehouse was equipped with an automatic sprinkler system. With the history of large-loss fires involving oxidizers, departments may want to reconsider this type of waiver. The likelihood of a fire in this type of occupancy challenging or overwhelming the automatic sprinkler system is a distinct possibility.
  • The entire east side of the warehouse had a railroad spur and was inaccessible to fire apparatus. Although this did not meet local fire codes, a variance was issued since an automatic sprinkler system was installed throughout the warehouse. Once again, based on the distinct possibility a fire in this type of occupancy is going to challenge or overwhelm the automatic sprinkler system, departments may wish to reconsider allowing this variance.
  • Companies must be familiar with the building through prefire planning so that all firefighters are aware of hazardous conditions. Based on first-due E-52’s familiarity with the building, members were aware of the hazardous materials stored inside the warehouse and immediately transmitted a second alarm and hazardous materials box when smoke was visible while they were still en route. Initial size-up on arrival called for defensive operations from the start, which was the correct tactic for the situation.
  • In this particular incident, the fire immediately overwhelmed the automatic sprinkler system, causing it to be generally ineffective. Fire personnel must keep in mind that if the automatic sprinkler system is in any way helping to control or extinguish the fire, the fire department connection should be charged as quickly as possible, preferably by an engine company from the first-alarm assignment. The sprinkler system provides a vast array of fixed nozzles already operating over the fire from the very start.
  • In prefire planning for fires involving warehouses storing oxidizers, it’s best to plan for the worst-case scenario. The prefire plan should take into account the likelihood that any fire developing in the area containing oxidizers could rapidly spread to involve a large portion of the warehouse before the first fire department unit arrives on scene. The plan must contain information that will allow command to make informative decisions regarding possible locations that can be used to cut off the fire spread. In this incident, the concrete block wall between Door# 23 and Door #28 turned out to be a good location to make a stand. There were limited openings in the wall that could be protected by handlines. The substantial nature of the wall allowed significant collapse to occur north of the wall without causing major structural damage on the south side, where firefighters were operating handlines.
  • It’s important for command to anticipate potential complications before they arise. In this case, command recognized the possibility of a significant brush fire at the rear of the warehouse because of severe drought conditions in the region. To handle this possible scenario, two brush trucks were special called to the scene at 10:40 a.m. for this reason. Luckily, enough rain had fallen on the morning of the fire to alleviate this threat.
  • The extra alarm assignments for the city of Dallas reduced the number of truck companies responding on each of the additional alarms. Based on the enormous length of this warehouse, multiple aerial streams were needed. As the fire progressed, command anticipated that need for additional aerial streams. Instead of trying to relocate truck companies from the north end of the building to the south end, command special called two additional truck companies at 11:02 a.m. in case the fire kept spreading.
  • The warehouse was in an industrial area with limited workers present on a Saturday morning. Even if evacuations had become necessary, this would not have required a major personnel commitment. Had the area been heavily populated and evacuations become necessary, this would have required a major commitment of city resources since the wind direction constantly changed throughout the incident.
  • Fuel levels on fire apparatus must always be maintained at acceptable levels to ensure operations will not be interrupted during the early stages of an incident. One engine company started to run low on fuel very early during this fire, and the city fuel truck was severely delayed in reaching the scene. The affected engine company was eventually switched out with another engine company on scene.
  • The original safety officer on the fireground was a BC. This chief was moved inside to monitor the safety of firefighters making a stand at the block wall between Door# 23 and Door #28. Command anticipated replacing the chief with an officer from one of the extra-alarm companies arriving on the scene. This duty was deemed a priority since the smoke given off by the fire was viewed as potentially toxic. However, as extra-alarm companies arrived on the scene, none of the officers were qualified to fill the safety officer’s role.
  • The fire prevention division must keep detailed records on file, especially for warehouses featuring high piled storage and hazardous chemicals. Fire companies and inspectors must monitor these types of occupancies to ensure key components of the fire prevention code are being followed. Specifically, warehouses featuring high piled storage must be inspected to ensure storage is not exceeding maximum height limitations and the commodity being stored has not changed drastically. This especially applies to the storage of hazardous materials. It is essential that the fire prevention bureau obtain a written statement from the building occupant (on letterhead) detailing not only the type and quantity of oxidizers being stored but also the method and arrangement of storage.
  • It’s important to remember that breathing apparatus must be used in an incident involving oxidizers until air testing determines that the quality of the air on the fireground is not a hazard. This applies also to firefighters operating outside the building.
  • When fire companies and inspectors notice new openings in fire-rated walls, they must verify that these openings are protected by a fire-rated door assembly. This provides the best chance for safely preventing the fire from spreading.
  • Address fireground problems with other agencies to ensure prompt response in the future. In this case, the transportation and public works department and electric company were requested early during the incident; however, both agencies were extremely slow to respond. Give specific directions to the agency knocking down unstable walls once the fire has been extinguished. Otherwise, as this fire showed, the agency will likely knock the walls into the structure, potentially destroying evidence for fire investigators.
  • Inspectors should take note any time in-rack automatic sprinklers are removed from a building. This should trigger a complete reevaluation of the fire protection systems for the property.
  • Although the oxidizer storage areas of this warehouse were physically separated from all other products, there were three different incompatible materials within the rooms that could have led to ignition (heat, rust, water). Inspectors must take into account all possible ignition scenarios and ensure that the incompatible materials are removed.
  • Never assume all fire-rated walls will be in place just because a building has a certificate of occupancy, especially when it involves Class 3 oxidizers.
  • Firefighters must continue to view concrete tilt walls as unstable during a fire.
•••

Fire and building codes are revised on a regular basis based on new testing data and fire loss experience. Unfortunately, there’s not a large amount of testing data available dealing with oxidizers. Documents such as NFPA 430 represent the best known methods for protecting buildings used to store oxidizers. Many of the requirements in this document come from previous loss history.

Factory Mutual Insurance does not have its own data sheet for oxidizer storage; instead, it references NFPA 430 for all requirements for this particular hazard. Fire departments must continue to become intimately familiar with the requirements in this document to keep firefighters and building occupants from encountering dangerous conditions in the future.

Endnote

1. See “Fire in Sprinklered Texas Warehouse with High Piled Storage,” Jeffrey A. Harwell, Fire Engineering, April 2012, for details of the first incident.

JEFFREY A. HARWELL is a fire protection engineer in Burleson, Texas.

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