Fire Studies: Overhauling and Salvage – Part 2

As noted in part one of this column in the December 2011 issue, overhauling in the fire service is “the checking of a fire scene to determine that no fire remains.” A close examination ensures that every location where hidden fire could still be burning is thoroughly searched. Salvage is the preservation of the structure and its contents from additional damage from fire, smoke, water and firefighting.

Part one focused on hidden fire, structural stability, structural overhauling and minimizing damage to fire buildings. This column focuses on protecting firefighters and preserving civilian lives and property.

Water damage

The best way to minimize water damage is to control all hoselines. This can be easily accomplished on a minor fire, but difficult when multiple streams are operating at various locations in a building. The basic rule when operating a hoseline is to open the nozzle when fire is encountered and close it after the fire has been knocked down. The exception is a fog stream that is being used to ventilate an area through a window or door opening. This ventilation can cause a smoldering fire to ignite. Firefighters can extinguish the fire with the backup hoseline or redirect the nozzle being used for ventilation to quickly extinguish the fire.

Basements should be checked for any accumulation of water. If water is found, pumps should be used to remove it. Stock on the floor can be elevated to minimize damage. Water accumulated on floors or roofs can create a dangerous situation. An immediate size-up can determine the best method of removal. Are there floor drains or scuppers to remove the accumulated water? An inspection may reveal that these systems may only need the drains to be cleared of debris to facilitate water removal.

We do not want a problem of water accumulation on a floor of a building to be solved by filling a basement with water. When removing water from a multi-storied building, dewatering should start at the first floor and then work upward to prevent a buildup of water on the lower floors.

A variety of tools can be used during overhauling. A pike pole or ceiling hook can be used for pulling lath and plaster walls and ceilings. There are tools that can effectively open large areas in plaster board or drywall to check concealed spaces. A prying tool can be used to open baseboards and moldings around doors and windows. The proven tools are the halligan, claw tool and axe, but many new lightweight tools can facilitate these operations.

Dangers from dust

A particular concern of firefighters performing overhaul is dust. Dust can commonly be found in woodworking shops, grain elevators, bakeries and other industrial occupancies. Combustible dust lying on a heated surface is subject to ignition due to carbonization of the dust. A cloud of combustible dust can be explosive. This occurs when the dust particles in the cloud are raised to their ignition temperature and come into contact with a source of ignition.

Once ignited, dust can smolder for long periods. Overhauling areas where there is smoldering dust demands a close examination to ensure extinguishment. This must include examination of exposed beams, rafters, ledges and other flat surfaces in industrial occupancies that are commonly associated with dust. A thermal imager is an excellent tool to detect smoldering dust fires. (A fire I had at the U.S. Mint involved smoldering metal dust that had accumulated over many years on flat surfaces high above the machinery. The fire was not spectacular and received little press coverage, yet it took a prolonged period of overhauling the large area to ensure complete extinguishment). Water will extinguish most dust fires and moisture will raise the ignition temperature of the dust. Care when operating hose streams around dust is important to avoid creating dust clouds. Fog nozzles should be used.