The most effective method of extinguishing a building fire is by an interior attack. At some fires, however, due to the area of flames, the high flammability of contents or combustible nature of the structure itself, an outside attack using master streams must be the strategy. Master-stream operations at rapidly spreading fire can be extremely dangerous – collapse, explosion, downed overhead electric wires and radiated heat are some risks.
Photo credit: Jay K. Bradish/IFPA
A wall of a burning building can collapse in one of three ways: a 90-degree-angle collapse, an inward-outward collapse or a curtain-fall collapse. The 90-degree-angle masonry wall collapse is the most dangerous because it creates the largest outward collapse danger zone. In this case, the wall falls outward from the building a greater distance than it would in either an inward-outward collapse or a curtain-fall collapse.
A wall that collapses at a 90-degree angle will fall straight outward, in a manner similar to a falling tree cut by a woodsman. It will cover the ground below with deadly bricks and timber for a distance at least equal to the height of the falling wall section. If a 25-foot-high wall collapses at a 90-degree angle, it would fall straight outward for 25 feet. No one within 25 feet of the building would survive; all would be buried beneath the collapsed wall.
Whenever there is a danger of wall collapse, plan for the worst – a 90-degree-angle collapse. Establish a collapse danger zone equal to the height of the wall, or even 1½ or twice the height of the wall, depending on your size-up. Withdraw all firefighters from the burning building for a required distance called the “vertical” or “outward collapse” danger zone.
After the vertical or outward collapse danger area is determined, the incident commander must also estimate how much of the wall’s horizontal area may collapse. This area is the “horizontal” collapse danger zone. For example, consider a 25-foot-high wall with a parapet extending over a row of stores, 100 feet long with a 10-foot-long bulge in the parapet at the center. In this case, the horizontal collapse danger zone may be a horizontal area 10 feet directly in front of the bulge or the entire length of the wall. The incident commander’s size-up must determine whether the masonry wall is tied together by steel reinforcement rods; in that case, failure of the small, 10-foot portion could pull down the entire wall. To be safe, a horizontal collapse zone should be considered the entire wall instead of just the unstable portion.
When a collapse danger zone is established, a fire officer must trade off the advantage of close-up hose stream penetration, through an open door or window of a burning building, for the greater advantage of the safety of firefighters operating in the bucket of an aerial platform. This practice conforms to the priorities of firefighting decision making: life safety first, including firefighters, and fire containment second.
The reach of a hose stream can be used as a safety measure. It lets firefighters move away from a dangerous wall and still discharge water on the fire. The typical reach of a handheld hose stream is 50 feet; that of a master stream is up to 100 feet. By using this distance as a safety device, a 50-foot hose stream could let firefighters operate 25 feet outside a collapse danger zone. The officer could withdraw firefighters 25 feet from a dangerous wall and still discharge water into a burning building from a distance of 25 feet. In this instance, by increasing fireground safety, maximum hose stream penetration is sacrificed; however, another hose stream could be positioned at another side or at the rear of the burning building to regain fire stream penetration. Such a fireground strategy increases fireground safety.
When there is no danger of wall collapse, the most effective use of an aerial stream from a ladder, aerial platform or snorkel takes place from close to the building through a window, door or other opening. Even when battling a fire in a one-story building, an aerial platform may be used at a low angle, close to the building. When large, plate-glass windows have been removed by flames or by firefighters for ventilation purposes, there is a large open area and, most importantly, there is no danger of wall collapse, a powerful stream from an aerial platform at a low angle can sometimes sweep the open space and quickly extinguish a large fire. However, when there is danger of wall collapse or where interior partitions or stock subdivide a row of small stores, it is less effective ,but safer to operate the stream from above. This strategy increases safety of firefighters operating in the basket or at the tip of the aerial.
Collapse Danger Zone For Aerial Streams
When a fire occurs in a multi-story building and there is danger of wall collapse, the incident commander and fire officers sometimes overestimate the capabilities of the aerial platform stream and underestimate the dangers to firefighters operating in the bucket of the aerial device. In some instances, we withdraw the ground firefighting streams away from a potential wall collapse danger, then let firefighters extend the tip of the aerial platform close to an unstable wall to extinguish fire. Sometimes, the aerial platform bucket enters the same collapse danger zone from which the ground forces are withdrawn from. This strategy is unsafe.
In recent years, an increasing number of building collapses have seriously injured firefighters operating in the buckets of aerial platforms. One reason for this increase in firefighters in the bucket being caught by wall collapse is the “arc” of a falling wall. The collapse danger zone for an aerial stream will vary from the collapse danger zone for a ground stream because of this arcing. When a wall collapses at a 90-degree angle, there is an outward arcing of the falling wall that could strike the bucket of an extended aerial platform.
All parts of an aerial platform or ladder truck must be positioned outside the collapse zone. This includes the truck and the bucket of the extended boom. To accomplish this, the apparatus must be positioned in the street outside the collapse danger zone and the raised aerial ladder, platform bucket or snorkel nozzle should never enter inside the arcing path of the unstable wall. When an aerial stream is operating and there is no danger of collapse, the tip of the aerial device may be placed as close to the building as possible.
Flanking a Fire
When a tall structure is involved with fire and there is danger of a wall collapsing, ordering a collapse zone could require firefighters to be positioned too far away. The hose streams do not reach the fire. For example, during a fire inside a church that is 80 to 100 feet in height, a collapse zone this distance would require ground and aerial streams to be operated 80 to 100 feet away to avoid falling walls. This would be ineffective. To counter this problem, a fire officer may position ground streams in a “flanking” position. To accomplish this task, an aerial platform would be placed in front of adjoining buildings, on one or two sides of the burning building, away from the unstable wall. The aerial stream’s range and effectiveness will be reduced, but the safety of the firefighters will be ensured, even if the unstable wall falls outward beyond the collapse danger zone.
Corner Safe Areas
Another safety procedure for protecting firefighters on aerial ladders using master streams is to use the corner safe areas around a burning building for placement and operation. When we look at a burning church from a bird’s-eye view, and imagine the collapse of all four walls of the structure, we see there are four areas where there are fewer bricks. They are the four corner areas around the building. These corner areas around a burning building provide the best chance of survival when walls collapse.
When setting up a fire operation at a fully involved church fire, or at any high-rise building that may collapse, these four corner areas around the structure are where the incident commander should consider positioning master streams. Because if all the walls collapsed outward simultaneously (which is unlikely) or one at a time, firefighters will have the best chance of survival in these four corner areas around the structure.
• The most effective method of extinguishing a building fire is by an interior attack. At some fires, however, due to the area of flames, the high flammability of contents or combustible nature of the structure itself, an outside attack using master streams must be the strategy. Master-stream operations at rapidly spreading fire can be extremely dangerous – collapse, explosion, downed overhead electric wires and radiated heat are some risks. At a rapidly spreading fire, apparatus initially positioned at hydrants or with ladders raised may have to be hastily repositioned away from the building to avoid these deadly events.
• Firefighters operating a telescopic aerial platform must be aware of the “rake” effect of the boom and bucket. When bedding the boom, first check for clearance below the bucket. Check the roof, parapet wall or fire escape below the bucket for clearance. Raise the boom first to clear any object, then retract the boom.
• The use of an aerial master stream at street level in a close-up approach to obtain deep penetration is effective only when there is no danger of a wall collapse and when there are no partitions to obstruct the stream. When there is a danger of collapse, the aerial platform stream should be used from above and outside the collapse zone. It may be less effective, but it protects firefighters.
• Establish a collapse danger zone. Firefighters must understand the collapse danger zone and position the fire truck and the extended bucket or aerial ladder tip out of the collapse zone. Firefighters in the bucket or ladder tip must consider the outward arc of a wall collapsing at a 90-degree angle. The arc may allow the wall to fall out farther and clip the top of the aerial device. The collapse danger zone can be the distance equal to the height of the wall, or even 1½ or two times the height of the wall, depending on the incident commander’s size-up.
• Use the reach of a stream as a safety tactic. A handheld hose stream can have a reach of 50 feet. A portable deluge nozzle or aerial master stream used from an aerial platform or tip of an aerial requires greater nozzle pressure and has a reach of up to 100 feet. Firefighters directing master streams should use this stream reach to position themselves away from the fire or burning building. A 100-foot master stream reach lets firefighters be 50 feet from the danger area and still penetrate the burning building a distance of 50 feet.
• Flank the fire. If a wall falls outward or there is a blast from the front of the building, firefighters positioned in the flanking areas (in front of adjoining buildings) will have a better chance of survival.
• Corner areas of a building must be considered by firefighters positioning master streams. There are four corner safe areas around a burning building. When you look at a building from a “bird’s-eye” view after all the four walls collapse, you see the four corner areas of the building foundation have fewer bricks. As one firefighter said, “It may not exactly be a safe area, but I have a greater chance of survival in the corners when walls start tumbling down.”
• All parts of an aerial platform or ladder truck must be positioned outside a collapse zone. This includes the truck and the bucket of the extended boom.
• Firefighters must know operating outside of a burning building can be just as deadly as operating inside a burning building.