STRIP WAREHOUSES: A NEW FIREFIGHTING CHALLANGE

STRIP WAREHOUSES: A NEW FIREFIGHTING CHALLANGE

BY BILL GUSTIN

When businesses follow the money to the suburbs, they can face zoning restrictions implemented to preserve the quaint “small-town” character of old established communities. As a result, new businesses in many suburban areas are relegated to “commerce” or “industrial parks” located on the outskirts of town. They will probably set up shop in a strip warehouse, a very common building in these remote commercial developments.

The strip warehouse is a favorite of developers because it can be constructed rapidly and rented to a multitude of mercantile, assembly, storage, and industrial occupancies. In my company`s response district, it is not uncommon to find a strip warehouse building occupied by a pizza parlor, a deli, a dance studio, a muffler shop, a carpet store, a cabinetmaker, a swimming pool supply store, a 10-minute oil change center, a printer, an antique store, and an auto parts store–all under one roof. These strip warehouses are a cross between a strip mall and a common speculative warehouse.

CONSTRUCTION HAZARDS

Although construction methods, materials, and requirements vary from region to region, strip warehouse buildings are commonly constructed with exterior walls of concrete block, tilt-up concrete, or a metal-clad skeleton of lightweight structural steel. Roofs generally consist of metal deck on steel bar joists; plywood on lightweight wood parallel-chord trusses; or, as is common here in Southern Florida, precast concrete twin “Ts.” Strip warehouses can be quite long–500 feet is not unusual–and are generally 40 to 75 feet deep. Buildings are divided into tenant spaces or bays, each with one to two overhead doors for vehicles and stock and one to two swinging, “storefront” doors–often aluminum stile with glass–through which customers enter offices, showrooms, and other public areas. Many strip warehouse bays are built back-to- back along a center dividing wall that runs the width of the building. Rows of bays built back-to-back commonly front on different streets or parking lots and have no door at the rear of the space, making front-to-rear cross-ventilation impossible.

Unlike its cousin, the strip shopping mall, strip warehouses have no ceiling to create a concealed overhead space. Typically, the underside of the roof is left exposed. Although this eliminates the problem of fire spreading inaccessibly in an attic or cockloft, it leaves the structural elements of the roof directly exposed to fire, whereas a ceiling (if so designed and installed) can provide a fire resistant barrier to protect the roof and delay its collapse.

The fire rating of and distance between walls that divide a strip warehouse into individual bays depend, of course, on the local building code. Similarly, the presence of sprinklers have a direct bearing on the spacing of fire walls/separations and the allowable size of tenant spaces. It is no coincidence, therefore, to find that the dimensions of strip warehouse bays are those stipulated in the code as the maximum size for which sprinklers are not mandatory.

In my jurisdiction, two-hour fire-rated partitions are required to separate warehouse spaces. This is generally achieved by constructing a concrete block wall between bays or attaching two layers of 58-inch type “X” (fire rated) gypsum board to each side of a metal stud partition. Many of these fire-rated assemblies are permitted to terminate at the underside of the roof deck. Some buildings may fall into the “unlimited area” provisions of the building code–effectively eliminating fire walls for many sprinklered one-story buildings of this type.

BEATING THE SYSTEM

Although a fire officer should be familiar with local construction requirements, building codes in themselves do little to ensure the continuing fire safety of a building once it has been constructed and is occupied. This is particularly true in the case of strip warehouses, where the interior construction of tenant bays can be vastly different from what the building department originally approved. Tenants occupying space in strip warehouses often construct their own offices, waiting rooms, showrooms, and dining areas without obtaining a building permit. Consequently, interior enclosures often end up being nothing more than poorly constructed wood-frame shacks built inside the shell of a noncombustible (read “not fire resistive”) building.

Sprinklers, if present, are almost never extended down into enclosed areas that have been constructed without permits, plans review, and inspections. I have seen some ingenious, unbelievable structures built inside warehouses, including an entire two-story residence!

Fire companies, therefore, must visit buildings in their response district regularly to identify code violations that would endanger them in a fire and to adjust their prefire plans accordingly. Building code violations are usually beyond the scope of a fire company officer`s authority and expertise and must be referred to the Fire Prevention Bureau or Building Department.

Unless an officer rolling up at a fire in a strip warehouse knows for sure that it is otherwise, he should operate as if dangerous, makeshift structures are inside the building. When it comes to interior construction, a cautious fire officer always assumes the worst. It seems that occupants of strip warehouses are limited only by their imagination, ingenuity, and what they can get away with. A typical case in point: A developer builds a noncombustible strip warehouse in full compliance with local codes. He receives “shell approval” of the structure (essentially an empty building) and begins to rent out bays to tenants who will occupy the spaces with a wide variety of businesses. One of the tenants rents a 3,000-square-foot bay for a floor-covering store. A strip warehouse is ideally suited to the needs of this businessman because he can freely move his large rolls of carpet in and out of the two overhead doors and receive his customers through the swinging, storefront doors. To open for business, the tenant must first obtain a certificate of occupancy. This is not a problem because his store, consisting of not much more than a counter and some carpet racks, easily passes all inspections.

Once in business, the resourceful store owner builds himself a showroom out of 2 2 4s, pressboard, and some inexpensive paneling. He then installs an air conditioner, insulates the overhead, and adds a drop ceiling with recessed light fixtures. Now customers enter through the storefront doors into a nice, comfortable sales area. Unfortunately, firefighters entering the same area under fire conditions will find themselves in a very dangerous place.

The top of the showroom soon becomes a convenient place to store pallets of floor tile and five-gallon buckets of tile adhesive. Business is good; before long, the store is ready to expand. As soon as it becomes available, the enterprising businessman rents the adjoining warehouse bay and, with or without the landlord`s permission, breaches an eight- by eight-foot opening in the fire wall. Later, he builds an employee lunchroom, a mezzanine for storage, and a second floor on top of the showroom for offices.

Although this business is replete with (code) violations, it might pass a routine fire inspection–if the fire company conducts one–because most line firefighters are trained primarily in firefighting and spend most of their time running EMS calls. Unfortunately, they are not very familiar with the requirements of the building code. Additionally, the fire company that inspects this store starts out at a disadvantage because it has no idea of what was permitted when it originally opened for business.

Now, let`s say that this illegal construction catches the eye of an observant inspector, who gives the tenant and landlord notice to correct the violations. Chances are that the businessman will demonstrate a willingness to cooperate by having an architect draw up plans to meet the intent of the code. This, of course, takes time. Then he will submit the plants to the Building Department for review, which can take a considerable amount of time in growing communities that have a lot of new construction. After the plans have been reviewed, provided that they are approved, the tenant will apply for a building permit and will probably be granted a “reasonable” amount of time to begin construction.

The businessman, who never really had any intention of bringing his store up to code, uses the plans review and inspection processes to buy time until his lease expires, at which time he simply will move his business and stick the landlord with a big headache. The landlord in all probability will be granted additional “reasonable” time to correct the problem. This is a common problem with strip warehouse occupancies, where tenants tend to be transient because it is cheaper for them to relocate their businesses than to comply with fire and building codes.

Ideally, flagrant code violations should be readily identified and corrected. Unfortunately, conditions are seldom ideal in the real world, where it is practically impossible to catch everyone who circumvents the system out of ignorance or greed.

THERE`S DANGER OVERHEAD

At the going rate of $8 per square foot for rental space, it would be naive to think that a tenant will use only the floor area of his warehouse bay. He, of course, will get his money`s worth and take full advantage of the volume available by stacking contents to the roof on racks; in lofts; and, in some cases, in entire mezzanines. These platforms are often poorly constructed and are overloaded. Additionally, they act as umbrellas, shielding the discharge of sprinklers that are operating overhead at the ceiling level. As they did in the carpet store, the tops of showrooms, offices, and other enclosures also make a handy storage loft. Unfortunately, they usually end up bearing a substantial load that they were never designed to support.

Storage

Firefighters crawling below the level of smoke may be unaware that over their heads are tons of storage that can fall and crush or trap them inside the burning warehouse. With building heights in the 25- to 30-foot range, there is plenty of space for heat and fire gases to rise and accumulate to dangerous concentrations underneath the roof while relatively tenable conditions exist at floor level. Firefighters attempting to locate a fire in a smoky warehouse can be unaware that a witch`s brew of heat and flammable fire gases is overhead.

I believe that this was a contributing factor in the death of a Metro-Dade fire lieutenant who was crushed in the collapse of a twin “T” warehouse roof and racks of rolled carpet. I believe that companies advancing a hoseline in heavy smoke were not immediately aware that fire was spreading across the tops of the storage racks and impinging on the underside of the roof. There is no failsafe method for accurately determining what conditions are like overhead. However, based on evaluations my company has conducted, I would venture to say that thermal imaging devices could be useful in scanning the overhead to observe the contrast of heat intensity below the roof, compared with lower levels. A stream from a hoseline directed momentarily overhead can be used to detect extreme heat at roof level. Cool water splashing down from above indicates relatively cool conditions, whereas hot water and the hissing of steam indicate high temperatures overhead.

Roof

I don`t know of any roof construction commonly used in strip warehouses that can withstand an intense fire for more than a few minutes. Remember, we`re dealing with relatively new buildings here that almost always employ some form of truss construction, which is prone to early collapse. Don`t be fooled by the appearance of roofs constructed of precast concrete twin “Ts.” They may look like heavy, substantial concrete, but they are far from being fire resistive. Similar to trusses, concrete “Ts” have elements in tension and compression. In this case, stranded cables running through the “T” are tensioned to several thousand pounds when the member is formed at the precast plant. The cables under tension exert a compressive force on the concrete, which allows the member to span several feet without supporting its center with a column or bearing wall. The steel cables are extremely vulnerable to heat that attacks and spalls the concrete at the bottom of the member. Exposure to heat causes the cables to relax their tension, which destroys the structural integrity of the “T.” Beware of concrete “Ts”–a few minutes of fire exposure can bring them down suddenly and without warning.

Lintel Beam

There is yet another overhead hazard in strip warehouses: The steel lintel beam that spans the top of overhead doorways can warp and twist from heat venting out of the opening. Deformation of the lintel can precipitate a collapse of the portion of the wall that it supports above the doorway opening. Of particular concern is the parapet, the section of wall that extends above the roof. The parapet is essentially freestanding and can easily break off and fall on firefighters operating streams through an overhead doorway. When heat attacks a lintel, apply a cooling stream and maintain a collapse zone equal to the height of a falling wall plus a few extra feet for blocks that can land at an even greater distance.

STRATEGY AND TACTICS

Strategy for fighting fires in strip warehouses is more likely to be appropriate when it is formulated with data obtained during prefire planning. Prior knowledge of construction, occupancies, hazards, and water resources will help an incident commander to make the most effective use of his companies and to ensure that they do not operate at an excessive level of risk. Fireground operations will proceed more smoothly and encounter less delay when officers can refer to a diagram of a warehouse complex that details building and suite numbers, access routes for apparatus, fire walls, and hydrant locations.

Make sure that your alarm assignment provides sufficient resources to handle an advanced fire in a strip warehouse and also maintain a tactical reserve for the unexpected. Fires in strip warehouses can quickly escalate beyond the capabilities of a first-alarm assignment as companies struggle to force doors and cut off fire spreading from bay to bay. Nighttime fires in strip warehouse complexes may be beyond the capabilities of first-alarm companies before they ever arrive. Delayed alarms are common in these remote commercial areas because they are usually deserted after business hours and fires can gain considerable headway before they are discovered. Companies arriving at a fire in a strip warehouse complex must resist the inclination to begin operations before the location, extent, and spread of fire have been accurately determined. Locating a fire in a 500-foot warehouse can be difficult and time- consuming, especially when all the businesses are closed. Without any positive indication, such as blistered paint on an overhead door, firefighters may have to walk the perimeter of the building, feeling each metal door for heat. During business hours, smoke issuing from an open overhead doorway can indicate the fire`s location, but don`t let the wind fool you! Hasty, premature commitment of companies at the location at which smoke is “showing” can result in wasted efforts and significant delay in getting water on a fire that is actually several hundred feet upwind. Accurate size-up, prior to going to work, is particularly important when long warehouses are built back-to-back. Smoke visible on one street could be from a fire burning in a warehouse space that fronts on another street that is totally inaccessible to companies who didn`t take the time to positively locate the fire before they put hose on the ground.

If possible, large engine and ladder apparatus arriving at a strip warehouse fire should stage at the entrance of the complex and allow smaller, more maneuverable vehicles, such as a chief`s car or small rescue truck, to proceed as “scouts,” to locate the fire and direct apparatus into the scene. In the absence of smaller vehicles, the officer of a large fire apparatus may have to order his company to stand by with the vehicle while he walks ahead to locate the fire. Maneuvering a large apparatus through a complex of strip warehouses can be comparable to trying to reach a fire in a trailer park, where drives are often too narrow and obstructed to allow apparatus to pass parked cars. Semitrailer trucks and garbage dumpsters can prevent apparatus from getting close to a fire building and force companies to operate beyond the lengths of preconnected hoselines. Even when it is accessible, the precious space in front of a fire building should be reserved for ladder apparatus and not be congested with pumpers that can readily distance themselves by stretching more hose. A congested strip warehouse complex is an ideal situation for a reverse hoselay.

Although engines equipped with large-diameter hose seldom have to perform a reverse lay to achieve adequate water flow, laying from fire to hydrant has some definite advantages: An engine company backs down to the fire or, if necessary, members hand-stretch their large-diameter hoseline to the front of the fire building. Firefighters can then operate handlines or master-stream devices connected to a portable manifold. The pumper then “leads out” to a hydrant and takes suction through a short section of large-diameter intake hose. A reverse lay thus clears engine apparatus from the front of the fire building and places them at the hydrant, taking maximum advantage of available water flow and pump capacity. Keep in mind the pressure limitations of large-diameter hose when supplying “friction loss-intensive” 134-inch handlines.

Sprinklers, if present and operating, are definitely an asset because they have already located the fire and can keep it in check, buying you time to find the fire, force entry, and advance a hoseline to complete extinguishment. As previously mentioned, storage racks, lofts, and enclosures often obstruct sprinklers in warehouse occupancies from discharging water directly on a fire. Therefore, don`t expect them to be 100-percent effective. However, the effectiveness of sprinklers can be increased by supplying them with adequate volume and pressure pumped through hoselines connected to the siamese connection from the first-alarm assignment.

ROUTES OF ENTRY

There are basically two routes of entry into a strip warehouse: a swinging door or one of the overhead doors that opens into each bay. If you must force your way into a warehouse, don`t choose your point of entry solely on the basis of speed or how easily a door can be forced. When selecting the route into a building, give due consideration to fire conditions, personnel safety, and the chosen route`s strategic value. Certainly, entering through a swinging door can be fast and easy. Breaking glass or pulling a lock cylinder, of course, is much easier than dealing with a heavy overhead door. But, where do swinging doors in strip warehouses usually lead? If you enter a smoky warehouse through a swing door, you will likely run head-on into a counter inside the entrance to an office or sales area. Then you will have to maneuver the hoseline through a narrow maze of desks and partitions inside a poorly built enclosure with literally a ton of storage overhead. The top of the enclosure and insulation in the overhead further endanger personnel. These barriers will prevent you from knowing the location and extent of a fire in the storage or work area and keep you from detecting dangerous levels of heat that threaten the roof structure.

When there are indications that a fire is small, such as one controlled by sprinklers, it is of course entirely appropriate to enter a strip warehouse bay through the office and open the overhead doors from the inside. But, when there are signs of a serious fire, you must carefully consider the risks of choosing a makeshift, poorly constructed, and overloaded enclosure as the point of entry.

Overhead doors are clearly more difficult to force than swinging doors and usually result in more damage. Selecting an overhead door as a point of entry, in a sense, violates a basic tenet of forcible entry: Try to force a door that the building`s occupants normally use to enter and exit the premises. This tenet, admittedly, has a lot of merit because the exteriors of overhead doors at commercial occupancies are usually devoid of locks, latches, and hoist chains. Typically, overhead doors at commercial occupancies are lowered and secured on the inside by an occupant, who exits the building through a swinging door. Remember, however, that you should not choose an entry point solely on the basis of how easily it can be forced. When safety, fire conditions, and strategic objectives permit, overhead doors have some definite advantages over swinging doors when you must reach a serious fire in a strip warehouse:

An overhead doorway provides direct access to the storage or work areas of a warehouse bay.

Overhead doors are usually directly in line with a main aisle, allowing hose to be advanced in a fairly straight line.

The height and width of an overhead doorway provide a large ventilation opening and escape route. Heavy streams operated through an overhead doorway can cool the roof structure, preventing a collapse. Bouncing a large stream off the underside of the roof can reach fire in areas that can be too dangerous to approach with handlines.

When possible, force overhead doors by cutting openings large enough to reach the locks, latches, and hoist chains; doing this will allow a door to be raised largely intact by its own mechanism. This method provides the largest possible opening for entry and ventilation with a minimum of cutting.

Door Styles

Modern strip warehouses are commonly built with one of three styles of overhead doors:

Overhead rolling. These doors consist of interlocking slats that travel up and down in guide tracks fastened to the sides of the doorway. The slats, which hinge on each other, roll up into an overhead drum, usually mounted on the inside of the building. New doors, designed to meet higher standards for wind resistance, are constructed with slats that are quite rigid, generally 22-18 gauge steel, which makes them much heavier than older models. Standards for overhead doors were revised because the force of high winds, which, when exerted on the face of a door, tend to bow in the middle of the door and pull the ends of the slats out of the guide tracks. “Smash-and-grab” burglars are well aware of this weakness and can quickly get into a building by bumping an older-style overhead door with their car. New doors, designed to withstand up to 56 pounds per square foot (psf) of wind load, are constructed with “wind locks” riveted to the ends of every slat or, at least, every other slat. Wind locks engage a channel in the guide tracks and prevent the wind, burglars, or firefighters from pulling slats out of the tracks.

Large, heavy overhead rolling doors are usually raised and lowered mechanically by a chain hoist or electric motor, assisted by powerful torsion springs inside the overhead drum that counterbalance the weight of the door. When a door is operated by a chain hoist, a continuous loop of chain extends from a large cog at the overhead drum down to a few feet above the floor. At this point, the chain may be padlocked to the guide track. Hoisting chains can be installed at either side of a door. There are some clues for determining their location. If a swinging door is next to the overhead door, chances are that the chain will be found on the side closest to the swinging door. When two overhead doors are side by side, the two chains almost always hang in between the doors.

Knowing the location of the hoist chain reduces the amount of time and cutting necessary to access the chain and raise the door. Cut a vertical slice along the track in the end of the door where you suspect the chain may be located. Continue cutting through the interlocking slats until the cut portion of the door can be pushed inward so you can look for the hoist chain, reach in, and operate the hoist to raise the door. If no chain is spotted, enlarge the cut to allow a firefighter to enter and raise the door from the inside, or repeat the same vertical slice in the other end of the door. The objective, again, is to raise the door normally with a minimum of cutting, but experienced firefighters know that this is not always possible.

It may not be possible to raise an overhead rolling door by its chain hoist mechanism for a number of reasons:

The door may be electrically operated. In heavy smoke, it can be difficult to figure out how to switch it to the manual mode.

Heat or the force of an explosion can warp the slats and prevent them from rolling freely into the overhead drum.

The chain or door itself can be secured with a difficult lock, or heat can attack the springs inside the drum, making the door too heavy to raise.

When it is determined that a door cannot be raised manually, you haven`t wasted any time with the initial cut(s) to access the chain. Go back and enlarge the initial cuts from as high as possible, down to the bottom of the door. Two vertical slices cut in each end of an overhead rolling door effectively cut each slat away from the wind lock that anchors it in the guide track, allowing the slats to be slid out of the door. Now, grasp the slats with vise grips and, while tapping the other end, pull the slats out of the door. Extremely long, rigid, or deeply recessed slats in a doorway may require a third vertical cut in the center of the door to reduce their overall length and make it easier to slide them out.

The old method of cutting a large triangle in an overhead rolling door is still a viable alternative to the preceding method and may be indicated when fire immediately behind a door necessitates a quick opening to insert a nozzle or when heat, corrosion, or mechanical damage prevents slats from sliding freely out of the door. The triangle cut or inverted “V” basically consists of two diagonal cuts that overlap at the top. It is easier to cut the triangle, however, when it is done in three parts:

1. Cut diagonally from as high on the door as possible down toward a bottom corner.

2. Make another diagonal cut toward the opposite bottom corner, but do not overlap with cut 1. Leave a few slats intact at the top of the triangle to keep the cut section of the door from falling into the opening as cut 2 is made. This will hold back some of the smoke that would otherwise obscure the saw operator`s vision and “choke” the saw`s carburetor. Also, if cuts 1 and 2 initially overlap, each slat will bend into the opening when it is cut, tending to pinch and bind the saw blade.

3. When you are ready to open the triangle, connect cuts 1 and 2 with cut 3, which will drop the entire triangle into the opening with a short cut of the saw.

The triangle cut always works, but it does not yield a very large opening, especially on newer doors. After completing the triangle cut, the opening is commonly enlarged to the entire width of the door by pulling slats into the triangle and out of the door. You may not be able to use this technique on newer doors that are equipped with wind locks to prevent slats from being pulled from the guide tracks.

Caution: Regardless of the method used to cut and dismantle an overhead rolling door, exercise caution when forcing entry. Powerful springs in the drum overhead counterbalance the weight of the door. The tension on those springs is adjusted to a specific weight–a substantial amount of weight on doors built to the new standards of wind resistance. Removing slats from a heavy overhead rolling door obviously reduces its weight and shifts the balance of tension/weight in favor of the springs. The door can suddenly shoot up with tremendous force, and you can be struck by the channel iron or bar at the bottom of the door or sustain deep lacerations as the loose, jagged ends of the door whip violently upward. A door separated from its bottom channel or bar will go past its stops at the top of the doorway and, like an old window shade, can spin around the drum until the springs dissipate their tension. Then just as suddenly, the door can drop back down into the doorway. When cutting and pulling slats from an overhead rolling door, anticipate that the door may suddenly rise at any moment, and be prepared to step back and wait a few seconds for the door to stop moving.

Also, heat can cause the springs to lose some of their tension, in which case the balance of tension/weight will shift in favor of the door, causing a door to close unexpectedly behind firefighters and leave them trapped inside a fire building. Without sufficient spring tension, a door can become too heavy to be raised manually to rescue the trapped firefighters. When an overhead door of any style is raised at a fire building, it should be held securely in the open position with a pike pole or by clamping a vise grip to the guide track. As an additional safeguard, wedge a halligan bar vertically in the track at the bottom of the doorway. This will give firefighters just enough room to crawl under the door if the first two devices fail to keep the door from closing.

Overhead curtain. This type of door operates the same as overhead rolling doors. It consists of sheet metal panels pressed together to form a continuous sheet that is strong yet flexible enough to bend and roll around an overhead drum. A curtain door is forced using the same method employed for an overhead rolling door: Cut a vertical slice in the end of the door, along the guide track, to access and operate the chain-hoist mechanism. If for whatever reason you fail to raise the door, go back and extend the initial vertical cut from as high as possible down to the bottom of the door. Then, cut diagonally, across the door down to the opposite lower corner. Do not connect the two cuts. Leave a few inches in between to keep the door intact. When you`re ready, make a short, third cut to connect the sides of the triangle; this will provide a large opening.

Sectional overhead doors. This type of door consists of hinged sections or panels that ride on rollers in guide tracks fastened to the sides of the doorway. Sectional doors on commercial buildings built to new standards for wind resistance are extremely heavy and are fortified by a strong reinforcing framework and a thick sheet metal skin. Cutting a large opening in a modern sectional door can take a considerable amount of time and blade material.

Sectional doors are usually locked by latch bolts that slide into holes in the guide tracks. Latch assemblies are fastened to the frame work of a door with sheet metal screws and are usually located on both ends of the second-from-the-bottom hinged section.

To force an overhead sectional door, cut small triangular openings in the second section. They should be large enough so you can reach in and throw the latches. Then raise the door, and support it in the open position. Cut only the sheet metal skin; avoid the framework. If the latches are padlocked in the tracks, cut the locks with bolt cutters or, if necessary, use a torch.

Cutting steel doors with a saw or torch can be dangerous because it in effect introduces two sides (heat and oxygen) of the fire triangle into a building. The grinding of an abrasive blade or the flame of a torch produces a shower of sparks that can ignite combustibles or, worse, trigger an explosion of a flammable accelerant an arsonist may have poured inside the building.

Companies in my battalion narrowly avoided an explosion when they were cutting an overhead door at the rear of a supermarket. A lieutenant, who was about to don his mask, got a strong whiff of gasoline and immediately stopped the operation. Investigators later determined that an arsonist had sprayed gasoline all over the sales area and set fires on a mezzanine, presumably as the “wick,” hoping that the fire would eventually ignite the gasoline-saturated first (sales) floor. Miraculously, it did not.

Air rushing into a poorly ventilated building (the oxygen leg of the fire triangle) can precipitate a backdraft.

Cutting an opening in the middle of an overhead door places firefighters in a dangerous position. Should an explosion occur, they will be vulnerable to being struck by and buried under a heavy door assembly. Cutting a door to access locks, latches, and hoist chains is somewhat safer because firefighters operate at the ends of the door and are in a better position to avoid the brunt of an explosion or falling door.

Fire conditions can influence how a door is forced. For instance, if you see only light smoke when you cut the first triangle, you may decide to enlarge the opening and send in a firefighter who can cut the padlocks, throw the latches, and raise the door from the inside. On the other hand, heat from an intense fire or the force of an explosion can warp and deform a sectional door so that it cannot be raised. Additionally, heat attacking the torsion springs that counterbalance the weight of the door can cause them to lose their tension and force firefighters to bear the full weight of an extremely heavy door. If you cannot raise the door, cut a large triangle for access. If this is necessary, it is faster to go back and extend the existing cuts than to start a new opening in the middle of the door.

There are many effective methods for forcing overhead doors. Your department must determine which work best for you. You may find that you will have to devise your own method based on the design and construction of the doors in your jurisdiction. Get out in your response district and familiarize yourself with the overhead door installations. Also, consult with overhead door contractors, who are a valuable resource of technical information on door design, construction, and operation.

Don`t rely on only one method of forcible entry. Firefighters experienced in forcible entry must have in mind a Plan B and sometimes even a Plan C for those times when their first attempts at gaining entry are not successful.

For strip warehouse fires, the life hazard, the risk to civilians and firefighters, must be carefully evaluated. Officers must weigh the realistic chances of their personnel becoming trapped and the potential for finding savable occupants inside a warehouse space against the risks firefighters will face while unnecessarily searching an unoccupied building. This is not to suggest that there couldn`t be a significant civilian life hazard in a strip warehouse, given the multitude of occupancies known to be in these types of buildings. I know of several businesses in my company`s response district where someone remains in the building at night with a shotgun nearby to prevent break-ins.

Once on an inspection, a nervous owner of a garment warehouse reluctantly allowed us up a narrow set of stairs to a loft built above his offices. There in a 20- 2 20-foot room sat a dozen Central American women at sewing machines. Certainly, the presence of civilians can only be positively determined by a thorough search. But in view of the combustible construction and hazardous contents common to many warehouse bays, a rapid attack on the fire is usually the safest and most effective way to protect firefighter and civilian lives.

With the potential for fire to spread from bay to bay, an incident commander must accurately project where and how big the fire will be by the time sufficient companies are on the scene to force doors and advance hoselines to cut it off. A miscalculation can result in companies` playing catch-up, chasing fire that has already spread past their positions. Predicting the spread of fire in a strip warehouse is difficult. Many factors must be considered, including but not limited to the following: building construction, fire walls, wind speed and direction, fire load, and interconnections between occupancies.

Generally, the strategy for confining a fire in a strip warehouse calls for getting ahead of the fire and using walls and unburned property as buffers between companies and the advancing fire. This strategy often requires that an incident commander have the courage and wisdom to write off the portion of the building already involved in fire and perhaps some of the threatened occupancies as well to make a stand. It would be unrealistic to attempt to describe a strategy that could be applied to every strip warehouse fire. Determining how much of a building should be sacrificed depends on two variables that must be assessed specifically at each fire: building construction and firefighting resources.

SCENARIOS

To illustrate the point, consider the following scenarios. As a battalion chief in a career fire department, you respond with your first-alarm assignment of three engine companies and one ladder, each staffed with a crew of four, to a report of a fire in a cabinet shop at the ABC Industrial Park.

Your companies are on the scene within five minutes and find heavy fire showing in the cabinet shop, with fire threatening the adjacent bays–a lawnmower shop and a pizza parlor. You are familiar with this building and confident of the integrity of the two-hour walls separating each occupancy. Based on your assessment of the construction and knowing that you have sufficient resources, you direct your companies to attack the main body of fire in the cabinet shop and to check simultaneously the adjoining occupancies for extension.

Now, let`s say that you are a chief of a small volunteer fire department responding from your home to a report of a fire at the XYZ Commerce Park. When you arrive, you find fire showing in a patio furniture store that occupies two bays in a strip warehouse of lightweight metal-clad steel construction. Fire separation between bays, you presume pessimistically, is nonexistent or has been violated over the years with several interconnections. Unsure of exactly how many volunteers can respond to this weekday fire, you consider the furniture store a loss, write off two bays on either side, and hope that you have accurately projected where the fire will be when your companies are ready to do battle.

You are definitely in an unenviable position. The area, contents, and combustible interior construction common in most strip warehouse occupancies require flows that far exceed those generally needed to suppress fires in compartmented residential buildings.

This seems obvious but can be forgotten by firefighters who are wed to fighting most of their fires with 134-inch preconnected attack lines. Although 134-inch preconnects can be fast and easy to deploy, they lack the flow necessary to effectively and safely extinguish an advanced fire in a strip warehouse commercial occupancy. Two and one-half-inch handlines and heavy stream devices provide the flow and reach to enable firefighters to knock down a significant amount of fire from positions of relative safety. In addition, large streams are more effective than small handlines at cooling the underside of the roof structure, preventing its collapse and, in the case of a metal deck, stopping the vaporization of roofing tar that can spread fire across the roof. A deck gun plumbed into the top of an engine can rapidly apply a master stream through an overhead doorway. Its value is limited, however, because its position on top of the apparatus restricts the range of its stream and prevents it from reaching into the overhead, where it will be most effective for suppressing fire in storage racks and cooling the underside of the roof.

Half of my department`s 40 engine companies are equipped with 50- or 65-foot telescoping booms. At serious warehouse fires, we will not hesitate to extend the boom low into an overhead doorway and operate its master-stream nozzle to knock down the fire. Then, after a careful assessment of the structure, as well as of the condition of any containers of flammable liquids or gases involved in the fire, firefighters will move in with handlines to complete extinguishment.

Ventilation is generally achieved through overhead doorways, which provide a large and fairly high opening. Conventional firefighting theory would have us cut a hole in the roof over a fire to control horizontal extension and relieve backdraft conditions. Modern strip warehouses constructed with lightweight trusses or precast “Ts” make conventional roof ventilation too dangerous–the undue risk of firefighter lives to save property. The message should be loud and clear: If a strip warehouse fire is serious enough to warrant cutting a hole in the roof, we have no business being on or under the roof. Strip or trench cuts in the roof in advance of a spreading fire can be a viable defensive tactic but should be attempted only with realistic expectations of the time, personnel, saws, and blades necessary to do the job. Warehouse bays built back-to-back are difficult to ventilate because they do not have a rear doorway to effect front-to-rear cross-ventilation. There is, however, a technique that is very effective in exhausting residual smoke from warehouse bays with no rear door after a fire has been extinguished. Some Metro-Dade companies carry a roll of 10-mil-thick polyethylene tubing, used to make plastic bags, which they duct tape to the positive-pressure ventilation (PPV) blower and extend into the warehouse bay to pressurize the space at the rear and force the smoke out of the front door. If at all possible, the blower should be positioned upwind to reduce the “churning” effect. The size of the exhaust opening can be adjusted by partially closing the overhead door. Caution: The plastic duct effectively clears a warehouse space of dense, residual smoke so that firefighters can see during overhaul. We have found, however, that the gasoline-powered blower tends to raise the level of carbon monoxide in the space. Hence, personnel performing overhaul must continue to use their SCBAs, and the space must be thoroughly ventilated before it is released to the occupants.

The rapid development of suburban areas has severely challenged many small fire departments that are struggling to keep up with their community`s growth. Expanding the mission of the fire service into disciplines such as EMS, haz mat, and technical rescue clearly increases a fire department`s value to its constituents but can further strain its resources to a point where it risks forsaking some of the basics of fire protection.

One of the most basic and fundamental functions of a fire department is to inspect, become familiar with, and preplan the buildings in its jurisdiction.

Strip warehouses with dangerous makeshift construction are a prime example of the reason firefighters must have a good working knowledge of fire and building codes and get out and inspect the buildings in their response district. The transient nature of many businesses that occupy strip warehouses means that the contents, configuration, and construction inside these buildings are constantly changing, requiring frequent visits by the fire department to update their prefire plans. Preplanning is essential to effectively fighting a strip warehouse fire without increasing the risk to firefighters. n

Strip warehouses are commonly constructed with exterior walls of concrete block, tilt-up concrete (top left), or a metal-clad skeleton of lightweight structural steel (bottom left), and are usually divided into tenant spaces or bays that have overhead and swinging doors. (Photos by author.) Tenants of strip warehouses often build–without a building permit–offices, showrooms, and even residences that generally are nothing more than wood-frame shacks–inside the shell of a noncombustible building (right).

(Top left) The substantial appearance of the precast concrete twin “T” construction of the roof of a strip warehouse can be deceiving. The roof is far from fire resistive. A few minutes of exposure to fire can bring it down suddenly and without warning. (Photos by author.) (Bottom left, right) The tops of offices and other enclosures are commonly used as storage lofts, which bear loads they were not designed to support. These dangerous overloads–which literally can amount to tons of materials–above their heads present hazards for firefighters responding to fires in these occupancies.

A cutaway of an overhead rolling door assembly. The wind lock (red) is riveted (rivets are black) to the end of the slat. The wind lock engages a channel in the guide track, preventing the wind, burglars, or firefighters from pulling the slat out of the track. (Photos by Justin Wasilkowski.)

To force a steel overhead sectional door, cut a triangular opening in the second-from-the-bottom hinged section (1). The resulting opening will be large enough for you to reach in and release the latch bar that is typically mounted on both ends of the second section (2). (Photos by Bill Lyons.) To force a curtain door, cut a vertical slice in the end of the door (3) to access and operate the chain hoist mechanism (4). If you are not successful, go back and extend the vertical slice. Then make a second cut, diagonally, toward the opposite lower corner and connect the two cuts, as shown (5), to open a large triangle in the door. (Photos by Justin Wasilkowski.) Intense fire behind this overhead rolling door removed the tension from the counterbalance springs and warped the slats so that the door could not be raised and the slats could not slide away from each other and out of the door. Under such conditions, the “old reliable” triangle cut works when other methods would fail. Note the deformed lintel beam above the doorway and the structural damage to the portion of the wall it supports (6). (Photo by author.) When any overhead door is raised at a fire building, always support it with a pike pole to prevent it from closing unexpectedly and trapping firefighters inside (7). (Photo by Justin Wasilkowski.)

Cutting a steel door with a torch or saw can be dangerous. Two legs of the fire triangle are introduced into a building: heat, from a shower of sparks, and oxygen, from air rushing through the opening. (Photo by Justin Wasilkowski.)

Firefighters roll plastic tubing, which is taped to a PPV fan and extended into the warehouse bay to pressurize the warehouse space after extinguishing the fire. This technique is excellent for exhausting residual smoke when there is no rear door and front-to-rear cross-ventilation is not possible. (Photo by George Izquierdo.)

BILL GUSTIN is a captain with the Metro-Dade County (FL) Fire Department and a lead instructor in the department`s officer training program. He has taught cruise ship crews firefighting skills, has instructed in Caribbean countries, and was a member of the International Rescue Task Force for the U.S. Office of Foreign Disaster Assistance. He is an editorial advisory board member of Fire Engineering.