COLLAPSE SEARCH AND RESCUE OPERATIONS: TACTICS AND PROCEDURES
PART 2: SIZE-UP AND SAFETY
This article, the second in a series on collapse search and rescue operations (See Part 1 in the May 1993 issue of Fire Engineering), discusses sizing up voids, evaluating hazard potential, and ensuring safety during operations, as preparation for an in-depth analysis of shoring and cribbing techniques.
To help the void team officer in the size-up, the nine-point acronym FAST. VO.I.D.S. was developed:
F – Fire
A – Additional collapse potential
S – Structure type and condition
T – Trapped occupants
V – Void type
O – Occupancy type
I – Immediate utility shutdown
D – Day or night
S – Situation that caused collapse
FIRE
The threat of fire always exists at any collapse situation. In addition, the possibility of an explosion always exists in the initial collapse stages, since gas lines or pressurized cylinders may have been ruptured as a result of the collapse.
All firefighters should be in full protective gear until all fire and explosion hazards have been fully addressed, which generally is not until the later stages of the collapse operation.
Fire spread through collapse void spaces will be rapid. Fuel and ignition sources can be located anywhere in the structure. Shorted-out appliances and free-hanging wires can suddenly ignite ruptured gas lines, leaking containers of flammable liquids, or fuel from equipment —trapping both rescuers and victims. A charged handline must be placed in a protecting position prior to void search operations. Firefighters operating at any collapse situation should be on constant alert to the ever-present danger of flash fire.
ADDITIONAL COLLAPSE POTENTIAL (SECONDARY COLLAPSE)
Secondary collapse is the most unpredictable and dangerous condition at any structural collapse operation. A thorough and ongoing size-up will determine if conditions call for shoring or removing unstable walls or floors prior to conducting void search, or if void search can be conducted immediately, Each building collapse has its own special problems, which should be addressed as the need arises. In larger buildings with extensive collapse, you may be able to search voids safely in one section of the structure while shoring operations are being conducted in another.
Vibrations must be factored into the size-up for secondary collapse potential. After a building collapses, some structural elements literally may be “hanging by a thread”; train, subway, and street traffic in the immediate vicinity must be rerouted from the area until the entire operation is over. Heavy earth-moving equipment also must cease operating. In a collapse with a large amount of hanging debris, which frequently is the case in multiple-floor collapses, even the noise and vibration of some tools, such as gas-powered chain saws, generators, or demolition hammers, may be detrimental to the operation. For safety reasons, vibrations must be kept at a minimum.
STRUCTURE TYPE AND CONDITION
An extensive amount of pertinent information can be derived from the structure type and building condition. Is the building old or new? Is it occupied or vacant? Was there previous fire damage? Is the building under renovation? Is it framed or unframed?
An older building usually indicates that structural elements may be fatigued, a definite problem when it comes to the possibility of secondary collapse. The exterior masonry elements generally take the most punishment over time. The constant abuse of weather causes the mortar and brick or block to constantly shrink and swell, creating a separation of the mortar and the brick, making the structure unsound. This condition is especially evident when two different types of material, such as steel and masonry or wood and masonry, are mortared together. Due to the different expansion characteristics of each type of material, the bond will be loosened and unstable.
Older buildings tend to be built with more substantial structural elements—a definite plus when it comes to secondary collapse potential. Structures built in the past 30 or so years often are constructed with lightweight structural members and systems. the result of better engineering standards and newer construction materials. While good for the builder and fine for the occupant under normal conditions, this technology can be a detriment to firefighters in a collapse (or fire) operation: Though the collapse debris will be lighter, the collapse itself will occur faster and be more extensive.
Depending on the time of day and type of building, collapse of occupied structures presents the distinct possibility that several or numerous victims may be trapped anywhere within the structure. Occupied buildings will be loaded with furniture, appliances, and other everyday living items, adding greatly to the amount of debris and the number of individual voids where victims may be trapped. Most occupied buildings tend to be wellmaintained, so sections of the building left standing will have a better chance of remaining structurally stable.
A vacant building, on the other hand, generally will be in disrepair and therefore structurally weaker. After the collapse has occurred, the stability of the rest of the structure will be extremely suspect. It must be watched constantly for any signs of secondary collapse. These buildings have less of a debris problem, since most, if not all, of the furnishings will have been removed. The possibility that victims are trapped is not as great in a vacant structure as it is in an occupied building; but unless you have information to the contrary —for instance, that there definitelv were no children playing in the building, no squatters living in it, and no pedestrians passing by at the wrong timeconduct a thorough search.
The void team officer must check for previous fire damage to the structure. This is very important. The possibility of previous structural damage directly affects the safety of the operating personnel. This damage may be hidden by alteration work undertaken to correct or conceal the damage. Suspect the building’s entire structural integrity if a serious fire had occurred in it, and conduct operations accordingly.
Structures under renovation have a unique set of problems. Many collapse situations are the result of unsafe and shoddy renovation work. In multiple dwellings under full renovation, it is not uncommon for the contractor to breach large holes in bearing walls to achieve better access to the numerous apartments. Renovators also have been known to make a large hole in every floor, each in line with those on other floors, for easy debris removal to the street. Walls and floors often are stripped down to the studs and beams. In short, the cumulative effect of careless renovation leaves the structure susceptible to collapse under any impact load: A wheelbarrow full of debris dumped only one floor can cause a major collapse.
How the building is constructed determines how it will collapse. In a “framed’ -type building, the floors and roof are not dependent on the walls for their support; they are hung on a skeleton-like framework, generally consisting of large structural concrete, steel, or heavy timber girders and columns. In a collapse situation, these elements can withstand and transfer extensive loads applied to them. Usually, a section of the building can collapse while the remaining structure stays intact. In this type of building, collapse can be relatively localized and not nearly as extensive as it would be in an “unframed’-type of building.
An “unframed” or wall-bearing structure is one in which the walls support the weight of the floors and roof. This is the most common type of building we encounter. Failure of any part of these walls can cause an extensive collapse, generating a large amount of debris and the potential for numerous trapped victims.
TRAPPED OCCUPANTS
The most important consideration at any collapse situation is the possibility that people are trapped. The goal of the entire collapse operation in that case is to extricate these victims. There are numerous ways to determine if and how many people are trapped or missing. Ilie most reliable method is by eyewitness accounts. Interview people at the scene and any survivors if at all possible; gather all pertinent information possible. Some of the most important points to cover are the location of the last room or area of the building in which the missing people were seen, how many there were, what they were doing, and the clothes they were wearing. If construction or other workers are involved, ask in which area and on which floor they were last seen operating and the kinds of tools or equipment they were using (if you find these tools or equipment first, the victim may be close by).
Check the entire collapse area for victims trapped near the surface. Remove these victims immediately. The next step is a more thorough search. You may choose to employ search dogs or some of the new, sophisticated search technologies available today. Remember, however, that the “round-the-clock” search method, developed during World War II, is very effective and possibly the quickest and easiest searching method. Several firefighters are stationed around the perimeter of the collapse area, all other personnel are told to be silent, and all equipment is shut down temporarily. Going in sequence, each firefighter calls out or taps an object penetrating the debris, such as a beam or a piece of steel. If a sound or reply is heard, the sequence continues until another firefighter hears the response and pinpoints it from another direction. Once verbal contact is made, maintain it continually to help the victim’s morale and gather any information that will help make the rescue easier and more efficient.
VOID TYPE
The type of void created by the initial collapse is the single most important factor in determining the probable location of the trapped victims and in offering the greatest chance for survival. Check these areas first when you do not have specific information on the locations of missing occupants. Six basic void types— pancake, supported lean-to, unsupported lean-to, V-shaped, A-frame, and individual —can be created in a typical collapse situation; it is not uncommon to encounter more than one type in a single collapse. (See “Part 1: Collapse Voids and Initial Void Search,” l’ire Engineering, May 1993 )
OCCUPANCY TYPE
The occupancy type indicates how many people may be in the building, how much equipment and machinery may be encountered, and whether possible fire and chemical hazards exist. Knowing the type of occupancy can provide invaluable information with regard to the possibility of entrapped occupants and their possible locations. If the building is a business or commercial occupancy, numerous people unknown to each other may have been working or conducting business in the facility, making it difficult to determine the exact location or the total number of occupants in the building at any given time. In incidents involving transient occupancies such as hotels, restaurants, and movie theaters, it is next to impossible to get an accurate head count of trapped victims. Searching this type of occupancy takes extensive time and energy. Numerous individual voids are created by machinery. equipment, and furniture; and every one of these voids must be searched. The possibility of finding yet another victim will have to be considered until the final general debris-removal stage is completed. In heavier brick-and-joist constructed buildings, such as factories or lofts, the collapse will cause large amounts of crushing debris with limited void spaces and limited void access.
In residential private dwellings, the collapse voids usually are extensive, due to the lightweight construction techniques generally used. Determining the number of occupants in private dwellings should not be too difficult. Begin by checking with neighbors, friends, or relatives in the area to determine if the occupants were home at the time of the collapse and how many people live at the site. In instances where it is uncertain whether the building is occupied, noting the number of cars in the driveway and die presence of toys or bikes outside the building can provide clues.
Determining the number of occupants in multifamily occupancies is more difficult, but it can be done with some accuracy. Check the number of mailboxes. Get a list of the tenants from the building superintendent, who can tell you which apartments are occupied, how many tenants are in each apartment, and tenants’ general work schedules.
IMMEDIATE UTILITY SHUTDOWN
One of the first actions you should take at any collapse operation is to make sure all utilities supplied to a building are shut down as soon as possible. Shut the gas down first because it is the most dangerous and could ignite easily, causing a fire or an explosion. The possibility of asphyxiation also exists. Shut down the electricity. since live wires present electrocution and fire hazards. Firefighters coming in contact with charged metal objects could be shocked or electrocuted. A spark created by firefighters’ tools contacting these wires could cause a fire or an explosion.
Water must be shut down. Leaking water pipes add substantial weight to rubble and make debris removal extremely difficult. It also is possible that someone trapped in the lower basement may drown. In addition, water can contribute greatly to an electrocution problem. Water accumulation also can undermine a foundation and add to the secondary collapse potential.
Check the atmosphere. For victims’ and rescuers’ safety, monitor all gases. Before entering any voids, check to see that oxygen is in the accepted range. If not, deal with the problem immediately. For example, insert a hose hooked up to an air compressor into the void, to bring in fresh air. Consider using SCBA. Check carbon monoxide. Pockets of this gas may have accumulated in low areas. Check the void with an explosive meter before rescuers enter. For maximum safety, continually monitor the gases during the entire operation.
DAY OR NIGHT
The time of day or night a collapse occurs affects the number and locations of possible trapped victims. For example, if a collapse occurs in a residential building during the night, the victims will tend to be in bedrooms and usually will be limited to family members, as opposed to including visitors as well. Interviews with survivors should make it easy to determine the number of missing occupants. When a collapse occurs during the daylight hours, however, it may be much more difficult to determine if occupants are at home. Immediately interview any eyewitnesses. Also consider that neighbors may have been visiting or other children may have been playing in the area.
The possibility that few people are in a commercial type of occupancy at night is very high. However, check these structures for security and maintenance personnel any time of the day or night, and don’t forget that some facilities have night shifts. At night, fewer hazards may be present inside a building, since much of the machinery will be shut down and equipment and stock generally will be put away. During working hours, most machinery will be activated, and people, stock, and equipment can be found anywhere in the facility. In such a situation, it is difficult to determine the number of missing occupants.
SITUATION THAT CAUSED COLLAPSE
Explosions, the impact of the collision, natural disasters, wall failures, the overloaded capacity of floors and roofs, structural weaknesses, column or arch failure, improper alterations, security measures, fire-weakened structural members—all are causes of collapse that have specific features or safety problems.
Explosions. These usually are caused by the ignition of undetected leaks of natural or propane gas, which when ignited can demolish entire buildings, resulting in extensive collapse, trapped victims, and numerous injuries. The structural elements of buildings that have endured powerful explosions have been subjected to tremendous strain. Do not consider any part of the building still standing to be structurally stable until a thorough inspection for stability is made.
Extensive amounts of debris and demolished construction material will be found throughout the structure. Experience has shown that injuries in such a situation will be severe. Victims may be trapped anywhere in the debris, and the number of survivablc void spaces may be limited.
Collision impact. This is an event that can happen in anyone’s response district. For any number of reasons, an automobile, truck, or piece of heavy construction equipment can go out of control and hit a structure, which many times can cause a collapse. These collapses generally are localized and are not too severe. The majority of trapped victims are located in the vehicle, but a compound problem exists—a vehicle extrication in a collapse operation Assess both situations. For the safety of the victims and rescue personnel, shore up and stabilize the structure before making any attempt to extricate.
When the collapse is more extensive, the possibility exists that building occupants may be trapped simultaneously with victims pinned in the vehicle. Survey the remaining portion of the structure for stability and, if necessary, shore it before trying to remove victims. This situation necessitates a two-pronged attack, which constitutes a difficult operation requiring extensive use of personnel and equipment, and the coordination of both teams.
Natural disasters. Weather-related incidents, such as earthquakes, hurricanes, floods, mud slides, tornadoes, etc., have caused tremendous damage, as witnessed recently in California and Florida. These situations cause extensive collapses, victim injuries, and extremely hazardous working conditions. The rescue teams must deal not only with the conditions of the collapse but also with the unpredictable conditions the weather brings on. These additional problems that must be anticipated make such a situation one of the toughest, most unpredictable, and most dangerous of operations.
Wall failure. Supporting walls can fail for a number of reasons. Two of the most common are foundation failure and deterioration of masonry structural elements. In “unframed” structures, this type of wall failure causes extensive, if not total, building failure. Large amounts of debris are generated, and the most common types of voids formed are the supported and unsupported lean-to.
Overloaded foors. Too much stock and heavy machinery and equipment are some of the most common reasons for floor failure. The additional weight applied to the floor tremendously stresses the beams. Even a slight impact load applied to the floor can cause beam failure, resulting in the victims’ being pinned under the stock or debris on the lower floors. The two most common types of voids formed are the V-shaped and the leanto, either unsupported or supported.
Overloaded roofs. HVAC units, large signs, and improper or blocked drainage ducts can constitute excessive weight for a roof. Extensive roof beam failure will cause the roof and its contents to have an impact on the lower floors, possibly causing a pancake collapse of the entire structure.
Structural weakness. While of major importance, this condition is one of the most difficult to detect because the majority of structural elements vital to the building’s stability are hidden from view by interior coverings, lath and plaster, sheetrock, and so on. Exposure and neglect cause a structure to age and deteriorate rapidly. A building that has suffered this kind of damage is extremely unstable. Almost any type of collapse void can be formed by the weakened structural elements and their connectors.
Column or arch failure. These structural elements generally give little warning before failing. If any part of an arch is removed or fails, the entire arch will fail. Any overhead elements supported by the arch generally will fail as well. If a column supporting a beam joint fails, a collapse will occur. The results of a column and arch failure are similar, and both failures generally will create a V-shaped void.
Improper alterations. This is one of the most common causes of collapse in an urban environment. An alteration is defined as new construction within a building that may change the building’s structural parts, mechanical equipment, or opening locations without increasing the structure’s overall area or dimensions, or as a construction project comprising revisions within or to prescribed elements of an existing structure that is distinct from additions to said structure. The type of collapse void formed depends on the extent of the alterations and the location of the collapse.
Security measures. In locations where security is a problem, owners of commercial properties may take extreme measures to protect them, including the use of heavy gates on the face of the building, which places excessive weight and stress loads on the front w all’s structural members. In some instances, these gates can pull down the entire front wall, causing extensive collapse damage.
Another, more dangerous, security measure is the use of steel-plated roofs and, occasionally, walls. Plating adds tremendous w eight to structures not designed to bear the w eight. Very little additional loading is needed to cause the failure of these structures. Because of the crushing weight of the steel and the difficulty in removing the remaining debris, this type of collapse creates a very limited number of voids wherein survivors may be found. The pancake-type void is the most common created by a collapse involving the enormous weight generated by such a collapse.
Fire-weakened structural members. When a collapse occurs in a structure that previously suffered fire damage, all of the building’s supporting elements are suspect. The structural integrity of all construction materials exposed to fire is not reliable. If any bearing members have been exposed to fire, then almost any type of collapse void may be created, since there is a lack of solid bearing. In addition, any sections of the building left standing must be thoroughly examined and must be shored up before any extended operation can take place.
CRITICAL SAFETY PRECAUTIONS FOR BUILDING COLLAPSE OPERATIONS
- Immediately shut down all the utilities supplied to a building. These utilities generally include gas, electric, and water. The combination of the three utilities can cause explosion, flash fire, and electrocution, drastically increasing the hazards for victims and rescuers. Eliminate these hazards as quickly as possible.
- Most collapses involving buried victims are extended operations. During daylight hours, lighting may be needed, especially in extensive void search operations. During dusk and at night, illuminate the entire area for the safety of operating personnel and for assistance in the search and rescue of trapped victims.
- Keep all nonessential personnel and rescue workers not immediately engaged in victim extrication or void exploration out of the collapse area, to minimize debris shifting or the unauthorized removal of structural supporting elements.
- Assign a safety officer to constantly monitor the stability of the remaining structure and adjoining buildings. A survey transit is extremely helpful in detecting any movement of unstable walls or floors. This instrument should be continuously staffed and any movement communicated immediately to the command post.
- If any substantial debris removal is to be initiated, the operations officer continually must evaluate whether to shore up or demolish specific areas of the collapse building. The two major factors involved in determining whether to shore up or demolish are the safety of operating personnel and the possibility that there may be trapped victims. If the slightest doubt exists as to whether any part of the structure is stable, the safest thing to do is to shore it. When in doubt, shore it up!
- Establish a collapse danger zone around the structure in question. The danger zone should be greater than the height of any of the walls still standing. All equipment, apparatus, and additional personnel should be ke pt outside of this danger zone. Remember, tiie safety of operating personnel is a priority; you do not need any additional victims in the form of rescuers.
- Have members work in teams under close supervision, and make sure all work is properly coordinated among the separate teams. This is done so that more work is not created for the rescuers. Proper coordination of debris disposal is a must to conserve time and energy. Ideally, collapse debris rubble should be handled only once. Relieve rescue personnel on a continual basis, according to the amount of debris handled and weather conditions. Relief periods of as short as 15 minutes or as long as 30 minutes work well. The command chiefs and line officers must maintain strict control of their personnel—-this is probably one of the most difficult tasks to perform at a collapse operation. The firefighter’s inherent aggression and quick actions could be a problem at a collapse operation, which must be handled methodically and safely. Members operating alone and out of sync with rescue teams are unsafe and totally counterproductive. Collapse situations are the most unpredictable and dangerous scenarios firefighters will encounter. Discipline must be maintained if the operation is to have a safe conclusion.
- Depending on the type of operation and depth of confinement, SCBA may be necessary. If any smoke or heavy airborne dust is present, the use of masks — even though they may be cumbersome —may be warranted. If necessary, insert hoses into the debris piles to gently feed fresh air in to trapped victims. If an extensive tunneling operation in a basement or subbasement is needed, confined space rescue procedures may have to be instituted.
- Begin immediately to constantly monitor all gases; take readings until collapse operations have been concluded. A hazardous response unit should be special-called for this purpose and in cases where dangerous chemicals are encountered and have to be removed. Do not attempt to handle the chemicals yourself. Wait for the haz-mat unit.
- Avoid any unnecessary shocks and vibrations. Have any subway or rail traffic in the immediate vicinity halted for the duration of the rescue operation. Limit the use of loud machinery and equipment and keep compressors and generators a safe distance from operating forces. Keep the use of gas-operated tools to a minimum if any part of the structure is unstable.
When operating in void search situations, check the oxygen level before entering any void. If it is below 19 5 or above 21.5 percent, take appropriate action. Continually monitor the carbon monoxide level. The use of an explosive meter is also warranted; pockets of residual gas from broken lines also may be present. Heavierthan-air gases will collect in lower void spaces and pose a threat to rescuers not properly protected.
