by Jeremy Simcheck
According to the U.S. Fire Administration, heating-related fires are the second leading cause of fires in residential dwellings, with chimney and flue fires accounting for 86 percent of heating fires. Couple this with the fact that ever-increasing fuel costs are driving homeowners to use more economical means to heat their homes and it is safe to assume that all jurisdictions will be seeing a substantial increase in the number of chimney fires.
In all cases, the design and operation of chimneys are very similar. Heat and smoke exit vertically by convection through the flue. This is often referred to as the "draft" of the chimney. A chimney fire occurs when the creosote on the inside of the flue liner ignites.
There are several factors that can lead to a creosote buildup, including not maintaining a proper temperature inside the flue, burning wood that is not dried thoroughly, or failing to clean the chimney on a regular basis. The type of construction and age of the chimney as well as the severity of the fire can affect the extension of fire outside the chimney.
Although search and rescue operations may not be necessary at a chimney fire, it is still imperative to ensure evacuation of the entire dwelling. Incident commanders should also ensure that responders use full personal protective equipment and oversee incident scene accountability and safety. The next priority should be directed toward fire confinement and extinguishment, including opening any areas believed to have extension from the chimney fire. Finally, perform salvage and overhaul operations.
Response and Size-Up
Treat any report of a chimney fire as a full structure fire response until the extent of the fire can be confirmed. Proper size-up is essential in determining the extent of the fire, since the fire may or may not be visible from the flue on arrival. Often, the fire may burn intensely only for a brief period and may have climaxed prior to the fire department's arrival. Be careful about cancelling other responding apparatus until a thorough inspection of the chimney and surrounding areas of the dwelling can be performed. Defects in the flue often cause small hidden fires inside walls, ceilings, and attics. Areas to be inspected include the appliance, as much of the chimney on the interior of the dwelling as possible, the attic, and the flue itself. Thermal imaging cameras are invaluable for inspecting hidden areas in walls and ceilings around the chimney.
Working on Roofs
Throw ground ladders and roof ladders where required. Once on the roof, remove chimney caps or bird screens to inspect the extent of the fire inside the flue. This can be made safer and easier by using a convex mirror attached to a short handle (Photo 1), which allows an initial look down the chimney without having to place your head over the flue. Watch where you place the creosote-coated chimney cap. Often, the material may still be smoldering and may cause a secondary fire if disposed of improperly.
Also keep in mind that chimney fires often occur at night and in less-than-ideal weather conditions, such as heavy snow or freezing rain. This can make working on roofs more difficult and dangerous. Heavy snow loads can also add increased weight to the roof system.
Photo 1. Click to enlarge
Extinguishment in Woodstoves
The first step in a fire involving a woodstove is to close the damper on the front of the stove. This will stop or greatly reduce the amount of fresh air being taken into the draft, usually causing the fire inside the chimney to diminish. Be careful when opening the door after the damper has been closed, as the sudden induction of air into the stove may cause a drastic increase in the volume of fire inside the stove and, possibly, the chimney.
Extinguishment actions must always be closely coordinated by the crews on the roof and in the interior. One common way to attack the fire involves dropping a dry chemical "bomb" (a quart size plastic bag filled with ABC Powder, Photo 2) from the top of the chimney. As the bag descends, the plastic melts and allows the dry chemical to coat the inside of the chimney and collect on any horizontal surfaces. Typically, no more than two bags should be dropped.
Photo 2. Click to enlarge
The roof crew can then drop a "chimney chain" (Photo 3) from the top of the flue. This will knock any creosote from the walls of the flue and cause it to collect at the bottom. The chain will usually have to be dropped several times, especially if there is heavy buildup.
Photo 3. Click to enlarge
Once the roof crew has finished dropping the chain, another crew should locate the clean-out door if the chimney is equipped with one. The door will be below where the metal flue pipe enters the chimney. If the chimney is on an exterior wall of the dwelling, the clean-out door will most likely be located outside. Remove any debris that has accumulated at the bottom and shine a flashlight up the flue. The roof crew will then be able to examine the amount of buildup left inside the chimney.
After the roof crew confirms the fire in the chimney is out, the interior crew can open the damper back up and remove or extinguish any material burning inside the stove. It may also be necessary to remove the metal flue piping from the back of the stove to ensure that the fire has been completely extinguished and to remove any residual creosote that may have fallen into the pipe during extinguishment.
Extinguishment in Fireplaces
The first step in overall extinguishment is to remove any burning material or extinguish the fire inside the fireplace. It is nearly impossible to work around the chimney with an uncontrolled, active fire at the base. The simplest method is a very short and gentle stream from a water extinguisher. The steam created will also help to reduce the volume of fire inside the flue. Discharge only a small amount of water to reduce runoff, which can cause substantial damage outside of the fireplace.
After the burning material has been removed or extinguished close the doors to the fireplace, if so equipped, or cover the opening with a fireproof salvage cover (Photo 4) to prevent dust from entering back into the dwelling. Then drop a dry chemical bag or use a dry chemical extinguisher to extinguish the fire similar to that used for woodstoves.
Photo 4. Click to enlarge
If dry chemical extinguishment methods are ineffective, there are commercially made chimney nozzles that can discharge a low-volume, fine mist of water into the flue. However, depending on the design of the chimney, the runoff from the stream could stain or damage the interior of the dwelling. Other water streams, such as handlines, should be used only as a last resort since they can permanently damage the flue lining.
Proper application of positive pressure ventilation (PPV) can greatly reduce the amount of smoke and dust inside the dwelling. PPV techniques should also be closely coordinated with command and the other crews, as it will often greatly increase the amount of air inside the draft and could lead to an increase in the volume of fire.
Following any chimney fire, instruct the homeowners not to use the fireplace until after it has been inspected by a qualified chimney sweep. Remember to take a few extra minutes during salvage and overhaul operations to use floor runners and fire-retardant salvage covers near the fireplace. Careful cleanup can earn your department valuable praise from the homeowners.
Jeremy Simcheck is the training officer for Gloucester (VA) Volunteer Fire & Rescue and has 13 years of experience in the fire service. He is also career fire captain at Langley Air Force Base in Hampton, VA.