Hot Fires in Big Boxes

by Alisa Wolf

Over the past 10 years, a new type of occupancy has taken hold in the United States, and it's catching on in Europe, too. It's bigger than a hardware store and has more traffic than a warehouse. It carries large quantities of lumber, plumbing supplies, electrical supplies, tools, fixtures, paints, homewares, garden supplies, appliances, and even food in some cases--you name it, these stores have it.

In addition to products that present ordinary fire hazards, these stores often carry products that present severe fire hazards, such as those made of Group A plastics. Patio furniture, toys, kiddie pools, wastebaskets, and other housewares fall into this category. Such stores may also carry paints, cleaners, aerosol products, flammable and combustible liquids, pool chemicals, and pesticides. And since these so-called bulk warehouse hyper-markets, or "big box" stores, such as Builders Square, HQ , HomeBase, Home Depot, and Lowe's, don't fit exactly into any of the occupancy classifications developed by the fire code community, protection schemes draw from standards as diverse as NFPA 231, General Storage; NFPA 231C, Rack Storage of Materials; NFPA 430, Liquid and Solid Oxidizers; NFPA 30, Flammable and Combustible Liquids Code; NFPA 30B, Aerosol Products; NFPA 43D, Storage of Pesticides; and the mercantile occupancies section of NFPA 101®, Life Safety Code®.

Because of the broad range of products stored, says Rick Mulhaupt, president of the NFPA's National Fire Protection Research Foundation, "most of these big box stores have been considered to be NFPA 231C occupancies, involving high-rack storage of commodity. Because there are small quantities of specialty chemicals, like pool chemicals, in some of these occupancies, there's been some uncertainty as to whether NFPA 430 should also be used for protection, either of the entire occupancy or at least the part that might have this kind of commodity."

In the past, some in the industry didn't accept NFPA 430's requirements for in-rack sprinklers for large quantities of oxidizers. In-rack systems inconvenience retailers, who want flexible shelving to accommodate seasonable items. In addition, stock must be treated carefully when in-rack sprinklers are installed, so that delicate sprinkler heads aren't damaged.

However, two big box store fires raised some questions about the real-world effectiveness of ceiling-mounted sprinklers alone for certain storage arrangements of specific types of products. NFPA investigated both of these fires, one in 1996 in Albany, Georgia, and one in 1995 in Quincy, Massachusetts. In both incidents, the fire grew more rapidly than anyone had predicted, even though the rack storage systems were protected by ceiling-only sprinkler systems. And in both fires, investigators found oxidizing pool and spa chemicals in the area of fire origin.

Albany, Georgia

The latest of these two fires occurred on Tuesday, April 16, 1996, at approximately 11:21 a.m. in an Albany, Georgia, store. Though the fire was traced to the area where oxidizing pool and spa chemicals were stored, the cause of the blaze was never determined. Once ignited, however, the fire spread through the rack of pool chemicals, producing large amounts of irritating smoke. The building's estimated 100 employees and 85 patrons safely evacuated the store before firefighters arrived minutes later.

First-responding firefighters reported that the building's structural integrity was already failing when they pulled up. They also saw smoke venting through the roof. Rapid fire growth had apparently overwhelmed the building's sprinkler systems, and flames had spread through the entire building, making an interior attack impossible. Eventually, fire destroyed the entire store and all the merchandise inside for an estimated loss of $9 million.

According to NFPA's fire investigation report, merchandise stored in the aisle of fire origin near the oxidizing pool chemicals included cedar, iron, and plastic furniture. Grill accessories, charcoal and lighter fluid, and charcoal and gas grills were also stored on the same double-row rack system as the pool chemicals; no vertical barriers separated the chemicals from these other products, as recommended by NFPA documents. The pool chemicals included sanitizers, algaecides, and chlorinators such as trichloroisocyanuric acid (trichlor) and calcium hypochlorite (cal hypo) which, according to the manufacturers' instructions, shouldn't have been stored near some of the other products without being separated by inert materials.

NFPA's investigators reported that, in addition to the lack of noncombustible vertical barriers, the store had deviated from NFPA 430's requirements by storing oxidizers on racks that were higher and deeper than the retail storage limits allowed. The store also deviated from NFPA 430 requirements by not protecting the stored oxidizers with in-rack sprinklers. And, finally, the sprinkler systems were designed to discharge densities and areas of operation below those required by NFPA 430 for oxidizer storage.

Quincy, Massachusetts

Less than a year earlier, a similar fire occurred in a big box store in Quincy, Massachusetts. This fire began at 8:23 p.m. on Tuesday, May 23, 1995, when 60 employees and 100 customers were in the store, which used a metal double-rack system throughout. As was the case in the Albany fire, investigators traced the fire's origin to the area containing oxidizing pool chemicals.

An investigation conducted by the Quincy Fire Department and the Massachusetts State Fire Marshal's Office traced the area of fire origin to the lower storage rack of stored pool and spa chemicals. Investigators determined that the fire was probably caused by a chemical reaction involving the pool chemicals and leaking motor oil packaged with lawn mowers that were stored nearby. The fire also involved Group A plastics and other combustibles that gave off heavy smoke.

According to Chief Thomas Gorman of the Quincy Fire Department, several factors kept this fire from destroying the building. Perhaps most importantly, the fire department was involved during the store's planning stages. Before construction even began, the fire department had made sure that an adequate water supply was available for the store's sprinkler system by insisting on a 12-inch looped sprinkler main rather than the 6-inch main originally planned.

"The fire probably would've overwhelmed the sprinkler system," Gorman says, "if we hadn't demanded some of these things."

The Quincy fire spread much like the fire in the Albany store, rapidly spreading through the rack of origin and into a rack across the aisle. Smoke developed so quickly that responding Quincy firefighters reported seeing heavy smoke as they approached the scene within two minutes of dispatch. Upon arrival, they reported that smoke was heavy throughout the building down to 5 feet off the ground. Noxious smoke that gathered thickly not just inside the building but in its parking lot, caused breathing problems for firefighters, 58 of whom were treated for minor smoke inhalation. Twenty-two sprinklers activated, and, with the help of firefighter hose lines, the blaze was contained.

Fire damage was limited to the rack of origin, two adjacent racks, and the roof. Direct fire damage was limited to approximately 1,000 square feet, but smoke damage was extensive throughout the store, and most of the stock was sold for salvage. No structural damage was noted, but the trusses and roof deck were heat damaged, and the store had to be closed for nine days due to smoke and chemical contamination. Damage was estimated at $4 million, and the fire alarm system was completely replaced following the fire.

Among the significant factors NFPA's fire investigators found contributing to the blaze were incompatible materials stored too near the oxidizers. Lack of in-rack sprinklers also played a role in fire growth, as did rack shelving of solid material and wooden slats that were placed too close to each other. Commodities stacked on pallets and wrapped tightly in plastic are also a consideration in any big box fire protection scheme, since the plastic on all four sides and the top can resist water penetration. Such encapsulated products were stored higher in this store than NFPA 231C allows without in-rack sprinklers. And stock items were stored in the aisles, which allowed the fire to spread across the aisle to adjacent racks.

Big box store hazards

Because of the volume of product sold in big box stores, the hazards normally associated with mercantile occupancies are intensified. According to Chief Gorman, high-piled storage constitutes one of the biggest potential fire hazards, since stacks of boxes can block sprinkler water spray.

"They use every inch of their space for selling," Gorman points out. "They're stocking constantly, all day."

Traditional hardware stores house products bought in larger quantities in a warehouse and bring them out as needed. In big box stores, however, the general public has access to all of the product. Unfortunately, storage arrangements that make materials accessible to the public can also clog aisles, as can shoppers and carts. Free aisle space is not assured, as it is in a more controlled warehouse arrangement, where only employees have access to stock. Stocking operations can also block flue spaces between racks, which are critical to effective sprinkler operation.

In addition to pool chemicals, big box stores also sell large quantities of combustible and flammable liquids, including paint and paint thinners. Gorman notes that incompatible products can be mixed when shoppers pick up an item in one aisle and, deciding against buying it later, lay it down on a product in another aisle. All of these factors can create a cumbersome situation for firefighters, notes Gorman.

"You need a lot of resources to fight a fire in these types of stores," he says. High staff turnover at these occupancies can also be a headache for fire departments trying to instill fire safety awareness and make sure personnel understand evacuation routes.

Most of these hazards were identified before the fires in Albany and Quincy. However, attention in the industry began to focus on pool and spa chemicals and the particular hazards of dealing with them in large quantities after state and local fire investigators identified them as a major factor in the intensity with which both these fires burned.

Although most oxidizers don't themselves burn, they can increase the burning rate of ordinary combustible materials and increase the fire's temperature. Some oxidizers support spontaneous ignition when they come into contact with incompatible materials, and explosions can result when chlorine from oxidizing pool chemicals reacts with nitrogen from certain algaecides and multipurpose A:B:C dry chemicals found in fire extinguishers. And although a severe fire can occur when pool chemicals come into contact with any incompatible material, the most severe fires occur when they interact with hydrocarbon liquids. In both big box store fires, certain organic liquids were stored near the pool chemicals, and in each facility, the fire grew rapidly, filling the building with smoke within minutes.

Because both fires burned more quickly and hotter than anyone had anticipated, it was in the best interest of these stores, as well as insurers and manufacturers, to test these chemicals and see what they were up against.

Setting the standards

The requirements for storing oxidizers in NFPA 430, which contained the most up-to-date information on oxidizers when these two fires occurred, are based on engineering judgement, not on actual fire tests. If nothing else, the two big box fires pointed to the need to test these pool and spa chemicals either to support the requirements of NFPA 430 or disprove them. David Nugent, vice president of Loss Control for Schirmer Engineering, collaborated with the NFPA Research Foundation on a new set of fire tests that will help develop documentation on the fire protection of bulk quantities of oxidizing pool and spa chemicals as marketed in big box stores. With the technical support of organizations such as the Austin, Texas, Fire Department; BioLab, Inc.; Industrial Risk Insurers; Lowe's Companies, Inc.; Olin Corp.; Schirmer Engineering; and Tomes Van Rickley & Associates, these tests were conducted during the spring and summer of 1997 at Underwriters Laboratories (UL).

The large-scale free-burn tests showed that trichlor presents a burning hazard equivalent to ordinary commodities, so it doesn't present a major concern, says the Research Foundation's Mulhaupt.

Cal hypo, on the other hand, causes fires that are more intense than imagined.

"I've never witnessed such fires in my life," says Nugent. "Nothing burns as hot as this stuff. It creates very severe fires."

In just over a minute, the fire, set between two half-pallets of cardboard boxes of cal hypo in plastic bags and later plastic bottles, filled the UL test chamber with billowing smoke and intense heat that overwhelmed the calorimeter and the room's venting capacity. The cal hypo also released vast amounts of oxygen and noxious gases.

Tests using sprinkler systems were also performed.

"Indications in our testing so far show that the ceiling-only sprinkler systems with a flow of 0.6 gallons per minute per square foot (2.27 liters per square meter) aren't adequate for cal hypo," says Mulhaupt. "Indications right now are that it's going to take in-rack sprinklers and compartmentation in stores that carry cal hypo in large volumes." This configuration, adds Schirmer's Nugent, is even more stringent than current NFPA 430 requirements.

How these findings affect the industry

These findings have major implications for the industry. Pool chemicals in most areas of the country are sold only for a few months a year. Once pool season is over, the big box stores return the unsold product and use the space for other commodities.

"We don't carry this product year-round in most stores," says Bob Oberosler, vice presidents of Lowe's, which was a fully funded partner in the recent fire research project. "This stuff turns over very quickly. At the end of the season, we send back what we don't sell."

Installation of extensive sprinkler systems for items carried only a few months a year could restrict the flexibility warehousers want. And piping in racks poses other risks, such as the chance a sprinkler could be knocked off by a forklift putting products on the shelves.

These concerns notwithstanding, Oberosler says that Lowe's is already looking at preliminary plans, either for the robust, in-rack fire sprinkler protection called for by the recent fire tests or for an alternate scheme to move the cal hypo outside, under a canopy open on three sides.

"That would limit our exposure inside," he says, "and would move the more reactive product outside, so if we did have an incident, it wouldn't pose as great a risk to life and property. "

However, Bruce Jacobsen, an NFPA Hazardous Chemical Technical Committee member from Olin Corporation, which manufactures pool and spa chemicals, points out that exposure to ultraviolet rays, sunlight, heat, rain, and inclement weather can compromise the chemicals' effectiveness and shelf life.

"We promote cool, dry, well-ventilated storage of the product, below 95°F (35°C), with a lot of air circulation, and this really doesn't happen outside," Jacobsen says.

While much of the detailed work on innovative protection schemes is yet to come, some changes have already found their way into the 1997 edition of the Life Safety Code®. According to Robert E. Solomon, NFPA's chief building and fire protection engineer, a specific section on bulk merchandizing retail buildings was added to Chapter 24, "New Merchantile Occupancies," and Chapter 25, "Existing Mercantile Occupancies." The tests, conducted at UL in the spring and summer of 1997, focused on cal hypo and trichlor, two of the most commonly sold oxidizing pool and spa chemicals.

"The new section of the Code will at least address the special egress issues associated with these facilities," Solomon says. So, for example, the Code requires that at least half of the store's exiting capacity be independent of the main entrance. Requirements for maintaining minimum aisle width for other types of mercantile occupancies also apply to these larger stores, as do requirements for employee training.

Code issues are also of concern to NFPA's Hazardous Chemicals Technical Committee, which will consider the results of the recent fire tests during the code revision cycle, scheduled to be completed in May 1999.

"NFPA 430 covers a wide range of liquid and solid oxidizers," Nugent says. "Now we know about cal hypo and trichlor-up until this point, we didn't. But we still don't have good data on other oxidizers."

In the end, says Carl Wren of the Austin Fire Department, who participated in the fire tests, fire departments and communities need to work with big box stores to develop cost-effective fire protection schemes.

"It's in our best interest to protect not only employees and the public," says Wren, "but the infrastructure of the community."

The popularity of such stores attests to the fact that the public wants them. And Mulhaupt is quick to stress that, based on the Research Foundation's fire test results, "these products in these occupancies are, in fact, protectable."

However, the potential for large fires is very real.

"We've been lucky," says Ed Comeau, NFPA's chief fire investigator, alluding to the potential for life loss in crowded big box stores.

Anyone who witnessed either the big box store fires or the recent fire tests conducted at UL would probably agree that it's up to everyone-from code-writers to enforcers to manufacturers to retailers-to make sure big box stores are safe places to shop and work.

® TM of the National Fire Protection Association

Reprinted from NFPA Journal, January/February 1998, p 50-54. Reprinted by permission of NFPA Journal.
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