SIZE-UP CONSIDERATIONS FOR HIGH-RISE FIRES

BY JAMES MASON

High-rise fires are dangerous for many rea- sons. One of the biggest problems in buildings higher than 75 feet is the low frequency of the fires that demand a hoseline be stretched. How many times have you arrived, checked it out, and reset the system and left? When a fire does break out, often there is still not much of a hose stretch because of the building’s installed systems. Most of the time, the sprinklers knock down the fire, and the fire department comes in to mop up. As these systems continue to be retrofitted into older buildings and newer buildings get constructed with sprinkler systems installed at the beginning of the service life, it is possible that there will be even fewer hoseline stretches in these buildings. This is not to say that sprinklers are bad. They probably save lives everyday.

Fire companies working in a response district with a full variety of structures will advance hose in single-family and small to mid-size multifamily buildings much more often than into the high-rise structures. Because of the lack of practice in this high-risk operation, when a hose stretch is needed, our size-up for the high-rise fire might fall back to what we respond to regularly and fail to address the differences between high-rise firefighting and the “typical” structure fire. Since sprinklers don’t work perfectly every time and many older high-rises may never get a system installed, a review of the size-up considerations and the dangers relative to the first engine’s hoseline placement can increase efficiency and safety at these incidents.

LOW-RISE BUILDINGS

When arriving on a first-alarm assignment in a building that does not rise above 75 feet, you can ventilate and quickly observe conditions. These factors are key to a successful hoseline operation. When you can reach the roof with the aerial ladder parked in the street, you can usually make the fire behave the way you want. The roof gets opened above the stairway or directly above the fire if it is on the top floor. The windows in the fire room can be vented on the way up the aerial or possibly from an outside, open stairway attached to the building, if one exists. The conditions lift in the fire room, and the line advances. The fire’s energy is released so it can travel in the direction it is looking to go naturally: up and out. The hose team advances under the lifting conditions while cooling down the fire and the remaining heat and steam vent out the open window.

Observing the conditions and sizing up when we arrive at a low-rise fire are easier to accomplish than at a high-rise fire. We can see more of the building and the situation on hand. Most changes in tactics that must be made because of the conditions can be called for at that time. Many times, the fire’s location and extent, the floor plan, occupancy, construction, and other important factors all can be determined from the curb. Firefighters are entering the building by going up through it but also around it and directly over the building to the roof, so any unusual conditions can be reported and addressed. An example of a condition that would be noted is a strong wind blowing against the side of the building that does not allow the fire room to vent out the window. Very often, at a low-rise structure, you are close enough to the fire floor so that you can tell what the wind conditions are at that level as you step off the rig. Also, if you should need to go defensive from the street, exterior streams would be readily available and all the firefighters should be able to see the need for quickly hitting the exposures of the fast-spreading fire.

HIGH-RISE BUILDINGS

When on the scene of a high-rise fire, the factors that contribute to a successful operation in a smaller building are absent from the start. At a high-rise fire, the observations you can make on arrival are of limited use in an upper-floor fire. The reflex time (the time it takes to receive the alarm and arrive on-scene, examine the annunciator panel, recall elevators, get off two or three floors below and walk up to the reported fire, verify the exact location, and hook up to the standpipe for the attack) can be 15 to 25 minutes. Because of the delay in getting firefighters and equipment to an upper floor, you can expect an advanced fire on arrival. Controlled ventilation of the fire compartment is also limited.

Along with of all these problems, the first engine officer must still consider conditions on the fire floor. The following questions arise: What will happen in the hallway when the door to the fire compartment is opened? How hard is the fire going to vent out toward the attack team? Will a frontal hoseline attack knock down the fire as it normally would in a smaller building, or should a different attack be considered? As can happen in any hallway used for advancing the line into the fire room, the conditions will change, but this change can happen quickly and violently in a high-rise. The hallway in which the hose team is working may be 200 feet or longer, and if the fire starts to win, there may be little protection. This article addresses several factors found in a high-rise building that are not present in a smaller building. They need to be considered when the first engine is sizing up for the first interior attack line.

In any structure, the fire normally will vent out of any hole of the compartment. Many times, the only option for ventilating and attacking the fire in a high-rise is the door through which the hose advances. This natural venting of the fire out of the door in a high-rise can normally be overcome by advancing a 212-inch hoseline with a 114-inch smooth bore nozzle attached. This line will flow about 325 gallons per minute and will protect the firefighters and allow them to advance. This large-flow hoseline will also help compensate for the delay in reflex time and the possible advanced location and extent of the fire.

Stack Effect

One problem common to high-rises but not found in low-rise buildings is the stack effect movement of air inside the building. A strong stack effect can draw into the hallway the heat and smoke from the opened entrance door used to attack the fire. Stack effect is the natural movement of air inside a building. It is created by the difference between the inside and outside air temperatures and the height of the building. As the height of the building increases, the stack effect can become more significant.

On a cold day, the air in the building will be heated and will rise in any vertical shafts such as stairwells, pipe chases, and elevator shafts. When both the stairwell door where the standpipe connection is made for the hoseline and the door to the fire room are opened, the stack effect can pull the fire’s by-products into the hallway. The heat can continue to be pulled to the stairwell and drawn up toward the roof.

On a hot day, the same action may occur on the fire floor hallway: The smoke and heat will be drawn out of the fire room by a reverse stack effect. The only difference in a reverse stack is that the cooling effects of the air-conditioning system will draw the heat and smoke downward in the stairwell. The direction of air travel up or down in the stairwells is not all that relevant to the engine operating the first hoseline in the hallway except for quantifying how hard it will draw the heat and smoke from the fire apartment when the door is opened.

The air movement in the stack effect can be greater on a cold day than on a hot day because the differences in air temperatures generally are much greater in winter than in summer. If, for example, the average inside temperature is 70°F and the outside temperature is 30°F, that would be a 40°F difference. On a summer day, the inside temperature would be about the same, but the hottest day ever recorded in Chicago was 104°F. The difference would be 34°F. Winter days in many northern cities can get much colder than 30°F, so the stack effect can also be greater.

A way to size up the stack effect in a high-rise is to note the weather conditions on arrival before entering the lobby. Is it very cold or hot out? When entering the lobby, you may encounter both revolving and swinging doors. If a swinging lobby door is used to enter, you will get an indication of what is happening inside. When opening the door on a cold winter day, notice if it feels as if it is stuck in the jamb. When walking through the door, notice if you feel as if the air currents are pulling you into the building. The door may also quickly swing closed behind you; it might even hit you in the heel as you walk through. If these things are happening, significant stack effect is occurring inside. Opening the door at the lobby is allowing air from the street in at the lowest level of the building. This is air that would not be allowed inside if it were not for the open, swinging door being entered. This new air is being drawn in and up toward the roof by the stack effect. The entire building is subjected to sort of a large venturi effect.


Figure 1. The stack effect will draw the fire’s by-products into the hallway on the lower half of the building. The lower the fire floor and the greater the difference between the inside and outside air temperatures, the greater the draw will be. This will occur during winter and will often be much stronger than reverse stack.

If it is a hot summer day and the door is unusually easy to open, if a rush of air hits you in the face as you walk through it, a reverse stack effect is occurring inside. The air being cooled from the air-conditioning system is filling the lobby, and this heavy air is leaking out like water in a bathtub as you open the door.


Figure 2. Reverse stack effect will draw products into the hall at the top half of the building because of the cooling effect of air-conditioning inside the high-rise. This will happen on hot days.

Once inside the lobby, check for the reported fire floor on the annunciator panel, and note the total number of floors in the building. Divide the number of floors in half. If it is a winter day, the lower the fire floor is in the building, the stronger will be the stack effect drawing the fire out of the fire room and into the hallway. If it is a summer day, the higher the fire floor is in the building, the stronger will be the reverse stack effect drawing it toward the stairs. If the fire floor is toward the middle of the building, the stack effect will be less intense in both scenarios. A point to consider about entering the building is that many newer buildings have swinging-door lobbies with two sets of doors instead of one. If this is the case, have a firefighter go inside to hold open the inside door so that the intensity of the stack effect can be assessed when the outside door is opened (Figures 1, 2).

Window Failure

Another problem in a high-rise that normally will not be found in a low-rise is window failure, which will create a wind that will blow the fire into the hallway. Windows can fail for a variety of reasons: the heat of the fire, thermal shock, or simply being hit with the force of the hose stream. Older, single-pane, wood-sash windows generally will start to fail at about 250°F. Thermal shock occurs when the window reaches a temperature at which the rapid cooling from cold water washing across it from the line will cause it to break. The older the windows, the greater a chance that this will happen. It occurs less frequently in double-pane windows. The inside pane may be hot, but the outside pane is still close to the outside temperature. A quick look at the first couple of floors from the street on arrival can help determine if window breakage might be a problem (photos 1, 2).


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(1, 2) Wood windows can fail from thermal shock or the force of the hose stream hitting the panes. Newer windows in high-rises are stronger because of double-pane sashes or tempered glass. Before initiating a frontal attack in a high-rise, consider the following: window condition, fire extent, the stack effect, wind at upper floors, and pressurization of the fire room. (Photos by author.)

It is more likely that windows will fail because of being hit by the forceful 21/2-inch hose stream. It may happen even when newer-style windows are present because of the force of the stream and the fact that the windows may already be weakened by the fire. In a frontal attack where the windows are opposite the hose advance, it might be good to bank the stream off the ceiling and the walls, both for the cooling effect on the fire and also to protect the windows from the stream’s force. A good backup firefighter using the hallway wall opposite the fire door to take the back pressure off the nozzleman can help with the direction of the stream when working with a 21/2-inch hose.

If the windows fail, the wind can blow the fire into the hallway. This is possibly the most dangerous situation when advancing the line in a high-rise, because the hose team may be working in a long hallway. After the windows fail, a strong wind pushing against the building’s fire side can push heat into the hallway extremely quickly. The typical fire loading of a small studio apartment occupancy (one with only a combination living room/bedroom, small kitchen, and bathroom, approximately 500 square feet) can fill the hallway with fire if the windows fail on the building’s windward side during windy conditions.

Further Assessment of Wind Conditions

Size-up of this problem can, again, start in the street on arrival. If any wind exists in the valley of tall buildings, the question to ask is, What is happening 300 or 400 feet above the ground? It is most likely that the wind is blowing at a much greater velocity as the height increases.

A second chance for investigating wind conditions on an upper floor comes when the engine company is on the floor below the fire making the standpipe connection. Some departments leave the engine on this floor while other firefighters go and verify the fire’s exact location. There may be a one- or two-minute wait for these members to get back to the engine company with the pertinent information. During this time, it may be possible for you to examine the room/apartment below the reported fire floor for wind conditions at this height.

Entering and chocking open the door to the room/apartment directly below the reported fire and opening the windows will give you a good idea of what the wind conditions are on the floor above. If the stairwell door that opens to this hallway is also chocked open, as it is when the hose is advanced on the fire floor above, the stack effect in the building can be added to a wind blown from failed windows. By quickly standing near the open windows and at the entrance door to this room one floor below, the wind conditions can be gauged: Does either spot feel windy, or do both feel calm?


Figure 3. A quick check can be done on the floor below the fire by standing first in position 1 to gauge any release of pressure from the room and stack effect when the door opens. Opening the windows and then standing in position 2 will allow a size-up of the wind if the windows fail. With the windows open, it may be necessary to return to position 1, as the door may act to squeeze the wind down to the width of the doorway and the effects might be felt here but not in position 2. This check in combination with checking the fire�s size and the windows� condition (original wood sash, for example) may cause the engine company to abandon a frontal attack in favor of breaching an adjoining wall for the fire room attack.

Windows can fail while the engine is advancing hose down the fire floor hallway or at the point when the door to the fire room is opened. If the windows fail at any point, wind blowing into the building will rapidly change the conditions on the fire floor. By performing this quick check of wind conditions on the floor below, the engine company can consider the safety of the members if a window fails. This check can be done in one minute or so if coordinated with the company members. If either spot on the floor below the fire feels particularly windy, the fire attack on the floor above may need to be done using a method other than a frontal attack. Breaching the walls to the fire room from the hallway or the room next door may be an option (Figure 3).

When sizing up wind conditions on upper floors in a high-rise, consider the following. If significant wind is pushing the fire side of the building, and if the widows fail while the line is advancing down the hallway, when the fire crews open the door to the fire compartment, they may not be able to handle the windblown push of heat from the room and may have to retreat. If someone outside is watching the windows with a radio to communicate their failure, the engine crew members can change attacks without opening the fire compartment door and endangering themselves. You can use a helicopter or have someone with binoculars on the ground to observe the windows.

On arrival, if the wind conditions are calm, expect that some wind will be at upper-floor heights. If it is windy on the ground, it most likely will be very windy aboveground. Wind at the upper heights of high-rises is very dynamic and will act in seemingly irrational ways, such as alternately gusting and then becoming dead calm.


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(3, 4) These louvered vents make the transition from the interior to the outside of the building when a heating/cooling unit (a univent) is present. These vents can allow a fire room on the windward side of the building to become pressurized in sustained, high-wind weather conditions.

In times of high winds, a quick “snapshot in time” investigation of the conditions on the floor below may not give a complete idea of what the wind will do on the fire floor. In these conditions, it would be prudent to work on the side of safety by investigating while controlling the door to the fire room, considering breaching adjoining walls to the fire compartment for the attack, or allowing the fire to burn down from a defensive position until the fire’s intensity lowers to a level you can handle. This defensive maneuver would rely on the building’s integrity to contain the fire to the original location.

When checking the room below the fire floor for wind conditions, a close look at the quality of the windows and their integrity may help the engine company decide on a fire attack strategy.

The initial high-rise hose stretch can also run into a problem in sustained windy conditions. In a high-rise, it is possible that the windward side of a high-rise can become pressurized from openings in the outside wall, such as window air-conditioners, univent heating units, and exhaust vents found in kitchens and bathrooms. The pressurization of the windward side of the building is slow enough to be undetectable by firefighters inside these areas. If the fire compartment is on the windward side of the building and the entrance door is opened, the fire can vent rapidly as the pressure is released into the hallway. This factor, in combination with the natural venting of the fire, which is searching for oxygen, the possible stack effect at the time, and a wind-driven fire should the windows fail, can accelerate deterioration of hallway conditions.


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(5, 6) Window air-conditioners can also allow a fire room on the windward side of the building to become pressurized during sustained, high-wind conditions.

If the response district contains high-rises, it is important to be aware of weather conditions that include sustained winds, which can pressurize the windward side of the building. Checking the floor below the fire, as described above, can help the engine company determine if a release of pressure is likely when the door to the fire compartment is opened for the hose advance.1 (photos 3-6).

There is one more safety consideration for the engine stretching the first line in a hallway at a high-rise fire. If hallway conditions turn untenable, an adjacent room or apartment can be used as a place of refuge if a retreat is necessary. Anticipate the need for such a refuge area, and force open the door to the room before you need it. If firefighters must retreat to the room, the door to the room can be closed and firefighters can call for help. Officers must determine beforehand which room should be used because blinding fire conditions may not allow firefighters much time to search for a safe room in an emergency. The room of refuge will also have to be cleared of civilians beforehand.

• • •

Advancing the first hoseline at a high-rise fire is quite different from advancing the first hoseline at a fire in a smaller building. Getting water on the fire takes longer, observations must be focused, and factors unique to a high-rise must be considered. As with any fireground response, the actions of the first-due companies set the tone for the entire operation. The dangers and the size-up factors related to the first-due engine’s hoseline stretch at a high-rise must be reviewed on a regular basis to fight complacency and ensure the safety of the hose team.

Special thanks to engineer and architect Scott Nacheman for his assistance with this article.

Endnote

1. White, Brian M. “Firefighting and the ‘High-Pressure Backdraft,’” Fire Engineering, Jan. 2000.

JAMES MASON is a lieutenant in the Chicago (IL) Fire Department, has been an instructor at the Quinn Fire Academy in Chicago, and is an FDIC 2005 presenter.

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