One of the commander's chief concerns during the plan had been the flanks of the attacking forces. He worried that the enemy would spread to the sides and try to outflank his forces. He included additional units in the plan dedicated to cover the flanks of the attacking forces. He was protecting the exposures.
Sound familiar? The battle on a fireground is no less a pitched battle that any army would fight. There are many of the same elements and one of the most important areas in firefighting strategy is covering the exposures.
The enemy in firefighting is heat the heat that the fire produces, where that heat can travel and the effect that the heat will have on other combustibles. Exposure problems are a result of excessive heat. The fire extends within the structure or to another structure as the result of heat transfer, which occurs in three ways: conduction, convection and radiation.
Conduction involves heat transfer by direct contact of the heated material to another material. The transfer of heat is dependent on the conductivity of the material. Many metals are good conductors of heat; brick is not. Masonry walls usually provide exposure protection because of the low conductivity of the masonry material.
Convection is the process of heat transfer through a circulating medium, usually air. When a fireplace heats a room, the movement of the heat throughout the room is convection. In a fire, the heated air rises and transfers heat to other areas as it spreads out.
Radiation involves the transfer of heat by rays or waves in all directions from the source of the burning. In a fire, heat will radiate in all directions until it strikes an object. The radiant heat will then be passed to the object by conduction. Radiant heat can pass readily through glass and air.
The severity of the heat threat will also be affected by time, distance and shielding. Time is the duration of heat exposure on a potential fuel source. The longer it is exposed and unprotected, the greater the heat buildup and potential for ignition.
Distance affects the heat transfer threat to an exposure because the closer a structure is to the fire source, the more threatened it will be.
Shielding of the exposure from heat provides protection by breaking up the radiant heat wave and reducing the ability of combustibles to reach ignition temperature.
Three basic types of exposures at an emergency scene must be addressed: life exposure, the internal exposure and the external exposure.
The life exposures are the problems and potential problems that the fire presents to people. These people include firefighters, occupants, other emergency responders such as police, and curious bystanders.
While occupants of the fire building would normally be removed to an area of safe haven, consideration also must be given to removing occupants from exposed properties. If the exposure requires that firefighting forces have to enter and examine the structure, then consideration must be given to relocating the occupants as an exposure risk.
Likewise, firefighters and other responders must be considered an exposure. The incident commander, assisted by the safety officer and sector commanders, must ask questions: Are firefighters wandering around in unsafe areas? Should firefighters who lack an assignment be re-directed to a manpower pool in a safe area? Is there a collapse potential that requires all personnel to be moved?
Yellow "caution" or similar marking tape is a good tool to control movement, not only of bystanders but firefighters. A proactive safety officer will mark areas at the scene with caution tape that will clearly define and give warning of collapse zones, no-entry zones or other unsafe areas on the scene. These marked areas must be clearly identified as no-entry zones for all personnel.
The curious citizen can present an exposure problem, particularly at large incidents. Everybody wants to take a look at the fire and to watch the firefighters in action. However, sometimes these curious bystanders can be exposed to smoke, toxic fumes and falling embers. Sometimes they just get in the way. For effective crowd control we need the police and need to call for their help early.
In some areas, fire police are available to handle crowd and traffic control. If you have fire police, make contact with them before the incidents occur. Discuss what your needs are going to be and what their role will be. Fire police should be instructed to check in at the command post to determine from the incident commander where to establish fire lines.
lnternal Exposures
The next exposure to consider is the internal exposure, created by the building itself to other parts of the building. There are six sides to consider for internal exposures: the four sides, the top and the bottom.
Heat usually travels up, so the most critical exposures become the floor above the fire and the top floor. The top floor becomes a problem because of the tendency toward mushrooming of the heat, smoke and products of combustion.
Heat and smoke seek the path of least resistance. That may be an open interior stairway or a shaft. The heat will rise until it hits an obstruction and then will mushroom or build up under the obstruction. Exposures above the fire present one of the priorities of our strategy. We stretch hoselines to the fire. Where's the next usual place that a line is directed? Above the fire, to cut off any extension and protect the most vulnerable area.
Fire can travel via pipechases and other void spaces to many parts of the structure. A pipechase is an open shaft in a structure where utility pipes for heat, water and soil are run from floor to floor. Fire traveling the pipechases can turn any incident into another long night.
At one incident involving a fire on the first floor of a three-story, row-type structure, firefighters had made an aggressive interior attack to control the fire in the first-floor apartment. As the incident commander, I had directed additional companies upstairs to check for fire extension to the upper floors or cockloft.
Since the first floor was well involved, I had instructed the companies to open all of the pipechases that they could find as well as the cockloft on the top floor for examination. The fire hadn't spread up the interior stairway, so if there was going to be any fire extension it would probably be by one of these routes. The search for extension was reported as negative and I turned attention to overhaul and salvage of the fire floor as well as releasing some of the companies on the assignment.
When the last-due engine company, the first to take up, was preparing to leave the fireground, the captain called me and asked, "Chief, are you sure that you want us to leave?" This is a good indication that there may be a problem brewing of which you, the incident commander, aren't aware. A quick inquiry revealed that from his vantage point down the block the captain could see smoke coming from the rooftop. A hoseline and some pike poles were put in service to contain fire extension to the cockloft.
What happened? The company searching for extension had checked all of the "normal" pipechase locations, such as the soil pipe shafts in the bathrooms. The firefighters had missed a pipechase used for heating pipes that was located in an unusual area of the stairlanding.
When sizing up a fire building to determine your strategy, consider the location of the fire and the potential exposures above it. A fire on the top floor of a four-story apartment house will have a primary exposure concern to the cockloft of the structure. If the fire is on the first floor, the exposure problem is magnified and now extends to the second, third and fourth floor as well as the cockloft.
I recently responded to a three-alarm fire in a five-story, U-shaped apartment building of ordinary construction with masonry walls and wood joist floors and roof. The fire started in a fifth-floor apartment and spread to adjoining apartments and the cockloft. It was an interior, offensive battle all the way. However, had the fire started on a lower floor and created additional exposure problems by spreading to several floors, it would have required several more alarms and could have ended up in a defensive attack and loss of the building.
Extension within the structure can be affected by the compartmentation of the floors. Open floor areas such as found in modern offices present a severe internal exposure hazard because there is nothing to impede heat travel and fire extension. A large area that is compartmented such as a residential apartment floor reduces the area that is exposed because of compartmentation.
While the most critical exposures may be above the fire, don't forget the possibility of fire dropping to a lower level. Fire can drop down via the same pathways that it can extend up through. It is a good practice to routinely check the floor or floors below the fire to ensure that no extension has occurred to a lower level.
External Exposures
In sizing up the fire scene, in addition to the internal exposures that the structure presents to itself, the incident commander has to consider the potential for fire spread to other structures. These structures are external exposures in the potential path of fire spread. In any structure the external exposures commonly include the properties on either side of the fire building, attached or not, as well as any property in the rear. There can also be a potential exposure problem in the front of the structure, depending on the width of the street.
The intensity of the fire will dictate the severity of the exposure problem. If the fire building is well involved, the external exposures may be severely threatened and require immediate attention. In some cases, the first hoselines will need to be directed on the exposures to keep them from igniting.
Sometimes, the fire will become so intense that the majority of hoselines will be directed onto the exposures to protect them from the radiant heat. Notice that the hoseline isn't placed between the fire and the exposure. This is a water curtain and is of limited value in a severe fire situation because radiant heat will pass through a water curtain. The water should be directed on the structure to absorb the radiated heat and provide better protection.
Many times the critical factor for prioritizing exposure protection is the wind direction and velocity. Properties that are in the direction of wind travel are usually more exposed and should be checked first. At large fires, firebrands and falling embers can cause exposure problems some distance from the fire building.
Fireground Strategy
Now that we've covered various types of exposures, what is the impact on the strategy set by the incident commander? Where do you start?
In the standard fireground strategy sequence that most firefighters have studied i.e., size-up, call for help, make rescues, protect exposures, confine, extinguish and overhaul the protection of exposures ranks higher than extinguishing the fire and right after rescue.
Two questions should be triggered upon the arrival of the first unit and should continue to be asked through the entire incident. All levels of command need to ask, "What have I got?" and "Where is it going?" Once this is determined, a third question is added to the sequence, "How do I control it?"
These three questions will prompt additional questions that can guide you in your strategic considerations. These basic questions can be built upon to provide a comprehensive package of information that you can use to determine your strategy.
Asking "What have I got?" should lead to additional questions such as: Is the fire big or small? Has it spread from the contents into the structure yet? How many floors are involved? Are all of the floors involved? Is it in the cockloft or attic?
The question "Where is it going?" includes: Are upper floors threatened? Is there a good possibility that it will reach the cockloft? Is there fire blowing out of the windows and doors impinging on an exposure? How close are the exposures?
Tactical Considerations
What does the term "protecting an exposure" mean? This can vary. lt may be as simple as sending a firefighter into an attached property to check for conditions. Many times, companies will stretch hoselines to cover the exposure and, in an attached property, need to open up ceilings to see whether fire is traveling in a common cockloft area or running the joists.
Determining the location and extent of the fire will help to prioritize the exposure protection. In a small room and contents fire, the priority will be to address the internal exposures first. While a hoseline is stretched to handle the fire, other resources are committed to check above the fire as well as adjoining rooms for any extension.
Exposure protection in these cases will be simple; if the fire shows any signs of extending into the ceiling area, a more thorough examination of the floor above is needed. Don't forget that even in a small fire, any attached properties should be checked. While the potential for extension may be small, companies should still check the exposure for smoke.
If a fire has taken possession of a floor or several floors, the exposure problems will be more complex. The potential for extension to an internal exposure such as the cockloft is almost assured. In addition, a serious fire creates a greater threat for extension to the external exposures.
When considering tactical priorities for exposure protection, remember that sometimes the best way to protect the exposures is to put the fire out. A fire that can be attacked and extinguished will usually decrease the exposure problems that you have to handle. Likewise, large-caliber streams directed on a large fire will reduce the threat and help to protect the exposures.
Another primary line of defense is a sprinkler system. It should be supplemented by engine companies and charged if needed. Hoselines can also be stretched to the sprinkler system of an exposed building. This way the system will be ready if it is needed for protection from the fire.
When checking the internal exposures of a structure, take advantage of built-in protection. Compartmentation may be designed into a large structure with the addition of self-closing fire doors. While checking for extension, if the fire door hasn't closed automatically or are partially blocked by some obstruction, clear the blockage and shut the door.
When determining if the fire is threatening external exposures, look at what type of obstructions are in the path of the fire and heat. Is there a blank masonry wall or are there windows or other openings in the wall? Windows will present a more serious problem because radiant heat passes through glass readily.
Don't gamble that the fire will behave in a reasonable manner. It will not. Be proactive when it comes to exposure protection. The result may be the difference between a good stop and a parking lot.
Bernard D. Dyer, CFPS, a Firehouse® contributing editor, is a battalion chief in the Philadelphia, PA, Fire Department currently working as an acting deputy chief. He has over 22 years' experience in the department. Dyer holds a master's degree in public safety from St. Joseph's University in Philadelphia and is a graduate of the Executive Fire Officer Program at the National Fire Academy in Emmitsburg, MD. He is also a state certified fire instructor.
