BURN ROOM INSULATION
TRAINING NOTEBOKK
“To adequately train a fireman, he must be subjected to heat and dark in a closed environment,” says Michael Eisner, captain of the Fire Department Training Center in Bellevue, Washington. Many fire departments are achieving this type of high-level training by using burn buildings—facilities in which they can ignite and extinguish fires repeatedly under controlled conditions.
“In such a structure, we can find out early in a firefighter’s career if he can cope with a catastrophic environment,” Eisner says. “We know his strengths and weaknesses faster and can bring him to a higher level of efficiency sooner.”
Eisner speaks from experience. The training center in Bellevue has been using a burn building to train the city’s firefighters as well as those from neighboring districts. Between 150 and 200 pallets are burned inside the building each year, allowing trainees to work in a live-fire setting on a regular basis.
BURN BUILDINGS VS. VACANT BUILDINGS
Although many departments have used abandoned structures safely and successfully for live-fire training, this method has become increasingly less popular since the advent of burn buildings. A fire in an abandoned building can be unpredictable. The personal safety of trainees is a major concern in live-fire training, and with abandoned structures the possibility of collapse and flashover present very real safety risks. Training in abandoned buildings increases liability risk as well, because fire conditions cannot be controlled.
In recent years the pollution caused by training fires has become a public issue. Many states, such as Oregon and California, now hold departments liable for the pollution they create as well as for any legal claims filed as a result of that pollution.
Relying on donations or other means to acquire abandoned buildings is, at best, a haphazard method when your’re trying to establish a regularly scheduled training program. Even when such structures become available, there are many time-consuming activities such as removal of electric wiring that must be completed before a fire can be set.
Structures built specifically to serve as burn buildings are a vast improvement over the abandoned-building method of live-fire training. Concrete, steel, or brick construction makes them safer, and pollution can be more easily controlled. Class “A” materials that emit hazardous fumes can be withheld from the burn, a feat not readily accomplished in an abandoned structure.
Burn buildings do have their flaws, however. The brick and concrete used in construction are very susceptible to cracking and spalling when exposed to the concentrated heat of training fires. They also can become weakened by the repeated cycles of heating and cooling. In addition, the brick and concrete retain some of the water used to extinguish the fires. When this trapped water is reheated in subsequent fires, steam develops, creating pressure severe enough to cause further cracking and spalling. Once cracks develop, the building’s structural integrity may be weakened, threatening the safety of trainees.
SACRIFICIAL SURFACES
Training officers, architects, and engineers have long sought methods and materials that would suitably protect burn room surfaces from the devastation created by fire evolutions.
One of the earlier approaches, which is still used today, involves “sacrificial” surfaces. These materials are expected to provide protection for a period of time, with ultimate failure being an accepted reality.
Examples of “sacrificial” surfaces are:
- Fire-retardcmt, treated lumber (4″ x 4″ or 6″ x 6″) placed tightly together and fastened to the walls and ceiling. With burns maintained at moderate temperatures (400° to 600°F) and fuel loads of reasonable levels, these timbers will char, may ignite, but nevertheless will continue to perform for quite some time before needing replacement.
- Concrete block walls as partitions. The blocks take the punishment and are less costly to repair or replace than the structural wall.
- Steel plates fixed to the interior surfaces. The obvious concern regarding conducted heat has prompted the placement of refractory insulation between the structural and steel surface.
The “sacrificial” nature is the warping of steel and refractory breakdown often due to moisture absorption.
Initial cost advantages of the sacrificial systems, however, often are offset by the expense of replacement, repair, and downtime. There is also a very real concern for safety in the selection of materials. Concrete block can explode, and superheated steel in a burn room presents a hazard in itself.
SELECTING INSULATING MATERIALS
Efforts have been made to convert existing commercial heat-resistant products to burn room applications. On the whole, these have met with only partial success, the reason being that excellent as these products may be for their intended use, they are not designed for burn room service. Those with acceptable “K” factors (transfer of Btu per square foot per hour per degree of temperature) often are lacking in density and unable to withstand the pressure of handline straight streams. Others are easily punctured or broken, allowing steam to develop behind the insulation, with resultant material failure. Cement products contain and absorb considerable amounts of moisture, making them susceptible to cracking from steam or freeze expansion. It is also difficult to find a manufacturer who will guarantee performance in burn room applications, which is understandable.
Burn room insulating materials should meet the unique and specific needs of the fire service. They should
- have thermal insulating properties to protect the structure from damage due to fires in the upper ranges of 1,000° to 1,200°F;
- have sufficient physical strength to accept physical abuse from firefighting operations,
- provide rapid, natural cooling to safe and tolerable levels—at which a firefighter without turnout gear can walk into the room;
- have low initial moisture content and superior resistance to moisture absorption;
- withstand thermal shock due to rapid heating and cooling;
- be unaffected by continued rekindling of fuel sources; and
- be serviceable without regard to atmospheric conditions or ambient temperatures.
Every insulating product will have its limitations when subjected to burn room service. However, when these limitations restrict training practices or schedules, search for a more suitable material. Restrictions concerning the fuel source, the proximity of the fire to the insulated surface, drying time between rekindles, and weather conditions all affect the consistency and effectiveness of training.
With the increasing trend in the past toward greater use of the broken stream in an interior attack, there is concern that burn room insulations cannot withstand the force of straightstream applications. Some have opted to use refractories or high-temperature cements in order to provide the surface strength desired. These products are generally quite dense—some in the range of 160 psi. However, this practice sacrifices insulation properties for surface strength, since the higher the density, the lower the insulating value. Consider that protection of the building’s structural members is a primary reason for the use of burn room insulation when you evaluate products of this type.
Furthermore, the high-density materials can add considerable weight to the walls and ceilings. The building must be capable of accommodating these increased loads without their creating structural weaknesses.
Base your final selection of a burn room insulation on individual training methods. Also account for specific evolutions, frequency of use, climatic conditions, and the structural condition of the burn building. Finally, extend the life of your burn room insulation system and increase burn evolution safety by installing and faithfully using a temperature monitoring system.
