NFPA Journal®, September/October 2012
Fighting basement fires is notoriously difficult and dangerous. The National Institute for Occupational Safety and Health (NIOSH) has investigated 18 incidents resulting in firefighter on-duty fatalities at basement fires since it began its investigation of firefighter fatalities in 1997. Underwriters Laboratories (UL) recently completed a series of experiments that included full-scale and laboratory tests comparing dimensional lumber and lightweight engineered support systems. As noted in the National Engineered Lightweight Construction Fire Research Project sponsored by NFPA in 1992, the lightweight support systems failed much earlier than the dimensional lumber, raising serious concerns about firefighters working on the floor above a basement fire.
This doesn’t mean firefighters should never enter a building with a known basement fire. Basement fires range from small, confined fires to blazes that involve the entire basement of a large industrial building with extra-hazard contents. Obviously, a small fire could become a larger fire, but a small contained fire should not, in most cases, affect the structural stability of the floor above.
Various tactics have been used to fight basement fires. One of the most frequently used — and the most difficult and dangerous — is advancing a hose line down a basement stairway. Opening the door at the top of the stairway creates a vertical vent, in which the fire and products of combustion will flow toward, into, and out of. If there is an advanced fire in the basement, it may be impossible or ill-advised to use the basement stairway. Unless the ventilation is coordinated with fire control, venting the basement using the stairway, or by other means, may cause a rapid increase in fire intensity, leading to a rapid collapse of the flooring system.
The fire service should become familiar with construction methods used in the response area and use this information, along with the UL report, to develop training programs and guidelines. Several NIOSH studies showed that firefighters did not know the fire was in the basement. Procedures and training objectives must address the need for an adequate size-up that includes making every effort to determine the location of the fire and access to the fire area. If the basement is partially above ground, additional tactics may be available, such as operating hose streams through a basement window. This tactic may allow entry into the basement by the stairway for final extinguishment. Pulsing, transitional, and indirect attacks could be used to knock down the main body of a fire in a basement that is partially above ground.
According to the UL study, standard measures that firefighters use to test a floor for structural stability, such as sounding the floor, thermal imaging, and floor sag, give some indication of an impending collapse, but are late indicators that are not entirely reliable. If these procedures reveal a weak flooring system, a prompt and immediate withdrawal from the area should be compulsory.
The offensive/defensive decision sets the stage for the entire operation and is crucial to firefighter safety. This decision is often made by the first-arriving company officer, who must decide whether to enter the building, but many of the indicators present at an above-ground fire may not be visible at a basement fire. It is important to have as much information as possible before committing to an offensive operation and to use the available information to evaluate the risk to firefighters.
For more on the Multiphase Study on Firefighter Safety and Deployment of Resources, visit firereporting.org.