Every month, the covers of most fire service magazines grab our attention with pictures of raging infernos or acts of bravery in the face of unspeakable danger; however, fire service veterans who have any amount of practical experience know that the daily realities of the business are reflected in runs and alarms that don’t paint such dramatic pictures or challenging scenarios. Of course, failure to appropriately manage any one of our seemingly mundane calls could lead to a department being the feature story in next month’s issue or on the Web–and not in a good way.
A blaze deep within the wood frames of residences is one type of fire that doesn’t necessarily present with rolling flames and prominent smoke upon arrival or first inspection, nor does it result in anguished victims waiting at window-side to be rescued. In fact, these calls may present with little, if any, physical evidence of a problem; the caller who reported the alarm may even start to doubt themselves when faced with a fire crew that can’t find fire or replicate the reported smell of smoke.
This situation presents a challenge to command and company officers, because it requires crews to pay closer attention than they would with an otherwise well-established fire when searching for and extinguishing flames. Fires within sills, headers, joists and other structural members can take hours to develop, because they can wait patiently for the right amount of air to create a working fire within the walls. As a result, the “fire detectives” must uncover the flames.
Define Our Terms
First, what is a sill fire? A sill fire is one that burns the sill plate of a structure somewhere between the masonry foundation and the structure of the building. (Note: A sill plate is the wood or metal that sits on the top of a foundation wall. They are attached to the vertical studs of a building.)
Depending on the age of the structure, structural member composition and condition, combustibles, oxygen supply and other burn characteristics, the fire may sit within the sill void–the space between the sill plate and the foundation–for some time, slowly burning the plate and extending to crossbeams, verticals and other combustibles.
The same holds true with headers, which are load-bearing beams separating the floors of a structure, and joists, which hold the flooring in place. Just like the sill area, fire impinging or involving these structural areas can slowly burn for hours, if not days, without detection.
Questions & Causes
With the possible exception of some unfinished basement or attic areas, sills, headers and joists are usually contained within sheetrock; suspended and acoustical ceilings; flooring; exterior siding and undersiding, such as plywood; masonry or decorative panels; beams and rafters. When confronting a suspected fire in these areas, officers and crews must ask themselves a couple important questions: Is there fire behind these areas? If so, how did fire get there and how long has it been there? And if I work to open up the void area, will I create a bigger problem before solving the smaller one?
Sill, rafter and header fires can be caused by various things, such as 1) cigarettes and other smoking materials discarded near compromised brick or masonry on building exteriors, which allows transmittal of heat from the cigarette directly to the wood component, or secondarily, to the component through another heat-transmitting source; 2) defects or deterioration in masonry in fireplace bases, flues and stacks within a structure (the latter two can transmit heat and fire into joists and headers as well); or 3) wiring that’s deteriorated due to age, rodents gnawing on it or because adjustments were made incompletely or improperly during reconstruction or remodeling.
The Inspection
The call received into the dispatch center may initially be for something as routine as a smell of smoke in the residence, without any alarm activation or visible fire, according to the reporting occupant. On initial inspection by first-arriving crews, no smoke may be apparent and there may be no active fire noticeable, but trouble certainly can be lurking just behind a faux brick wall or paneling, or even under a carpet or subflooring. Unless drawn to a specific area of a structure by the presence of smoke or fire, those first on scene should perform an inspection that’s thorough enough so they can avoid the mistake of hastily starting to return companies and recommending to the homeowner to call if trouble “really” starts.
A full walk-through of the structure, including and especially the attic and basement areas where it’s easier to see floor joists, sills, and headers, is the crucial first step to take. Ample support from newer technology, such as thermal imaging cameras, along with some older tools like heat guns, can strongly increase the odds of finding the source of the smoke or more confidently dismissing the original complaint. A complete review of the occupant’s previous day of activities can also be helpful.
Other indicators to look for or ask the resident about:
- Movement of and/or issue with a high-draw electrical appliance, which may be an indicator of a problem within the electrical wiring that runs through or along structural members.
- A fire in the fireplace the previous day, which may be directly related to a fire in the floor or walls around the mantle masonry.
- A prolonged but unremarkable odor in one or two specific areas.
- Homeowners or contractors doing repair or remodeling work. Thawing pipes with torches is always an important consideration during winter months. Remember: Remodeling can drastically alter the appearance of a structure. Be aware of older buildings that may have originally been constructed with balloon-frame construction, but have since undergone remodeling that now masks the underlying construction type.
General knowledge of construction, as well as knowledge of specific local codes, building age and building construction types in the immediate vicinity, can also help crews determine whether effective fire blocking could have been or is being used. Fire blocking–the closing of pathways within construction techniques via the use of wood or other products–is found in many building codes and is an accepted method for limiting air flow through sill plates and other open areas within the skeletal components of a structure; however, it may not be in your building code, it may not be used if the structure pre-dates such requirements, it may not be installed correctly or completely, or it may be compromised or abridged since first installed. And although fire blocking techniques can be very effective in stopping the spread of a fire, even those installed according to code may not prevent the start of a fire, the long festering of a fire or the spread of a fire in a direction that the blocking was intended to prevent or limit.
Inspection Hole Caveats
Inspection holes in walls and floors, based on diligent investigation with all the human senses and the tools we have with us, will likely be necessary, but with a couple of caveats and forewarnings. First, the introduction of air through the inspection holes may well turn a small, smoldering fire into a roaring fire in just a few minutes, so it’s critical to be prepared with the proper fire-suppression capabilities before venturing into these void spaces. Second, “uninformed” inspection holes–or scattershot damage without a direct link to the findings of the initial investigation–could also become a customer service nightmare that’s far worse than any potential fire, so keep the residents informed as to the “whys” and “hows” of doing some preemptive physical damage to their home. Finally, inspection holes, if they’re done on the exterior of the home, could create other circumstances for the homeowner, even rendering the structure uninhabitable, so try to avoid any structural damage along the way.
Tear Down = Fire Found
Consider this: A crew’s inspection holes have revealed a small and deep-seated fire condition within the walls of a structure where the vertical supports meet the sill, or, fire has been found to be eating away slowly but progressively at a header behind the fireplace. Having stretched a precautionary handline to the exterior and with pressurized water cans on the interior, opening up the affected areas can proceed safely and effectively, with water being applied as necessary to knock down the fire.
Question: How far do you go in breaking apart a wall? The simple answer: Go far enough to make certain that the fire is out. But the harder question is, as it was from the outset of the call, do you commit personnel, and risk the ire of your homeowner, to further tear-down activity when you think that the hole plus the water has pretty much done the job? A simple rule of thumb, damage notwithstanding, is to go so far as to see where the burn stops on a 360-degree basis, and then go a little further.
Notable Examples
My department responded to a recent case that involved the breaking down of a brick and mortar fascia surrounding a first-floor fireplace box to the extent that the whole header running behind it was revealed. By opening up this non-structural wall, crews were able to see 1) the seat of the fire, which by this time had produced significant amounts of smoke but not much visible fire; 2) the extent of the fire, including its full vertical and horizontal paths of travel; and, 3) the type of damage, which warranted the calling in of the local building official given the compromised condition of a load-bearing header beam.
During another alarm, which was called into dispatch as a possible structure fire with smoke in the first-floor apartment of an occupied multiple dwelling, investigation revealed a basement fully charged with smoke from a long-simmering sill plate fire. While the fire was contained to the sill plates without extension into the vertical supports or flooring underneath the first floor, it produced a lot of smoke, which poured out of the forced-air heating vents and into the occupied areas of the structure.
Despite the relatively minor nature of the actual fire, extinguishment required the tearing down of a front interior hallway floor and threshold so crews could access the seat of the fire. Initial impressions were that it was an appreciable amount of damage, but without it, the fire would have continued to survive on the available air until it a) reached a much greater source of air; b) found a new route of travel, offering both more advantageous fuel and air sources; or c) continued to pour toxic smoke throughout the HVAC system. This call was somewhat unique because there was a large amount of smoke upon arrival but no discernible source of fire, rather than it being devoid of any apparent physical characteristics.
A third call required the tearing apart of a fireplace base because the fire had traveled through cracks in the mortar on the floor of the fire box and onto the sill plate of a home that was constructed on a concrete slab. The slab limited the access to the sill via both the exterior walls and the decorative masonry in front of and below the fire box. No access from below was available given the home’s type of construction. This incident presented with little more than a smell of smoke, and the only additional information firefighters were given was that the homeowner had been using the fireplace earlier in the day.
There have been other, notable examples of incidents in which crews were called out to “a smell of smoke” that they determined to be unfounded, only to return hours later to find a major fire and significant life hazards. The most prominent of these might be the March 2005 incident in Teaneck, N.J., that took the lives of four children only hours after firefighters had been called to the house for a smell of smoke. While that case involved a compromised electrical system (which can be a source of a fire in a sill or header) in the basement, it still illustrates the importance of thorough investigation.
Don’t Be Afraid to Open Up
For chief or company officers, one of the toughest challenges with fires in sills, headers, joists and other construction features will be to contain the second-guessing among crews and homeowners while you aggressively investigate and suppress these stubborn and often hidden fires.
Damage can often be perceived, especially among civilians, as damage for damage’s sake rather than as part of a coordinated and well-developed plan of attack based on years of experience in mitigating major events. Without the presence of smoke and no visible fire, and without a trained eye, education and patience, many inside and outside the fire service will erroneously conclude that efforts to inspect, open up and extinguish are exaggerated or ill-advised given the seemingly unthreatening character of the situation at hand; however, those well experienced in engine and truck company management and thorough firefighting will know that the efforts undertaken during that call will prevent the department from becoming the subject of next month’s magazine cover.
Sidebar: Fire in Sills & Other Structural Components: A Detective’s Guide
Command and company officers, as well as firefighters, are all asked to do a little detective work when faced with the possibility of a fire deep within the structural components of a building. Here are a few rules to live by when dealing with these types of fires:
- Assume nothing and check for everything. The call was precipitated by something the occupant heard, smelled or touched. It’s our job to find out the “why,” “how” and “what” of the situation.
- Do your due diligence. Thoroughly examine the entire structure, including attics and basements, crawl spaces and exteriors. A smell of smoke that’s unaccounted for could be coming from any of those places.
- Talk to your occupants. Find out what has gone on in the structure over the past 24 hours, and ask what led them to call the fire department. Then combine that intelligence with your knowledge of the structure type, building construction and fire/smoke behavior in order to effectively serve the customer and keep your crew safe.
- Systematically eliminate potential sources. Smoke from a heating vent may indicate a problem with a boiler, or a fire condition in the vicinity of an air exchanger. But don’t just pin down the location of smoke or fire, also determine the source for these conditions as well, and open up wherever your investigation leads you.
- Be prepared for the consequences of opening up. The introduction of air into a confined area, especially within the structural underbelly of a building, could precipitate an acute growth in the fire condition.
- If fire is found, suppress it; if not, remain alert. Advise the occupant that a fire condition was found and extinguished, and in the debrief, include not only what was done but why it was done in that manner. Alternatively, advise that no fire or smoke could be detected, and instruct the occupant to remain alert to further signs of trouble, and to call the fire department if they have the slightest sense that something is still not right.
- Don’t worry about time. Taking the time to effectively deal with the situation at hand is much wiser (and safer) than returning hours later to spend several more hours operating at a major structure fire precipitated by a failure to detect, explain and suppress at the earlier alarm.
Following these rules and your training as firefighters and officers will result in a successful operation.
