Residential Fires
Donan Engineering has a team of certified fire investigators throughout our service area to handle residential fire investigations of all varieties. Our investigators possess an array of specialized expertise and experience that enhance their capabilities. Donan Engineering’s investigators have the proficiency to complete your assignment in a timely and cost-effective manner with the highest level of certainty and professionalism.
Residential fires make up nearly 80 percent of the fires investigated by Donan Engineering each year. Single-family dwelling fires make up the majority of these residential fires. Single-family dwelling fires are caused by a wide variety of ignition sources. Some very special considerations must be addressed when investigating single-family dwellings, and all recognized publications on fire investigation must be followed.
Fire investigators will generally begin the site study with an exterior survey of the structure, as many variables must be evaluated. Information regarding the time of day the fire occurred and the elapsed time from fire discovery to the arrival of fire department personnel are crucial. This information may easily explain or be a cause for concern regarding the amount of fire damage noted on the exterior of the structure. Donan Engineering prides itself on a great working relationship with fire departments throughout our coverage area, and will even provide training to fire departments regarding origin and cause determination.
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Tactics employed by a fire department during suppression efforts may cause fire damage and burn patterns to be something other than what would typically be expected with regard to the size and location of the fire. Water application and ventilation, if improperly coordinated, can cause rapid fire spread and distorted burn patterns. Donan Engineering’s fire investigators have extensive experience and training in fire extinguishment tactics, which enhances our ability to determine what affect the employed tactics had on the remaining evidence.
Many single-family dwelling fires are witnessed by the occupant of the home. Often, the fire is directly linked to some type of human act, error, or omission. The occupant does not always acknowledge this human act if he or she was involved. This lack of acknowledgement can cause some exceptional challenges for the investigator. The investigator must be able to determine if the information gained during the investigation is consistent with the physical evidence that remains after the fire. In many instances, the occupant and/or owner believes his/her involvement will negate insurance coverage. In other instances, an intentional human act is responsible for the fire. If the physical evidence remaining after the fire is not consistent with the statements made by witnesses, the investigator must determine why the inconsistency exists. Donan Engineering’s fire investigators are trained in information-gathering techniques that will provide our client a complete and concise conclusion.
Single-family dwellings are not normally subject to routine inspections by building officials or fire marshals. This lack of inspection from outside entities leaves the care, maintenance, and usage of many heat-producing appliances at the discretion of the occupant. This arrangement can lead to many deficiencies that are potential fire causes. Donan Engineering’s investigators are knowledgeable in the operation of heat-producing appliances found in the home. Our fire investigators have numerous mechanical engineers at their disposal to assist in complex evaluations of appliances.
One of the most often modified and altered systems in a house is the electrical system. Many people believe they have the expertise to add, remove, change, or modify the electrical circuitry of their home. However, these modifications can lead to disastrous outcomes. Donan Engineering’s fire investigators are trained in the recognition of sub-standard installation and repair. Our investigators analyze the failure mode and preserve the evidence in the event further joint studies are required.
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When an electrical event is believed to be the cause of a structural fire, a complete and extensive evaluation of the entire electrical system is imperative. In our investigations, sub-standard workmanship or electrical code violations during construction are commonly identified as the cause for the fire. We have the ability to involve our on-staff electrical engineers to assist in the origin and cause determination.
Most appliance manufacturers have a structured and well-outlined procedure for maintaining their equipment. Water heaters, for example, must be properly installed and maintained to guard against fire-initiating failure. Manufacturers also explain vividly the importance of keeping both the outer and inner combustion doors in place to separate the open-flame burner from ordinary combustibles near the unit on gas-fueled heaters. Water heater installation can also be the cause of residential fires. Water heaters that are installed in atmospheres possibly containing flammable vapors (such as in garages) are to be elevated a specific distance above the floor as outlined by local building codes. The routing of the vent piping on gas-fueled water heaters can also be a potential ignition source if the recommended clearance to combustibles is not maintained. Electric water heaters do not contribute to as many fire causes as gas-fueled units. This does not eliminate them as a potential fire cause, as high resistance electrical connections are also possible. Donan Engineering’s fire investigators are trained to recognize fire causes involving water heaters.
The furnace is another potential residential fire cause encountered by fire investigators. Just as with water heaters, the combustion chamber of a furnace must be completely separated from combustible materials. The installation of a vent pipe system is also a consideration in determining fire cause. Even more important with the furnace—as it produces over twice the amount of BTUs of a water heater—specific code requirements must be adhered to with respect to clearance from combustible items.
In the last 10 years, a new innovation in the construction industry has caused fire investigators great concern: Corrugated Stainless Steel Tubing (CSST) used for whole-house gas piping systems. CSST is a continuous flexible gas line used today in many new and retrofit applications. The rise in popularity of CSST is due to the ease and speed of installation; many hours of labor are saved during the construction of a single-family dwelling by using CSST instead of conventional black iron pipe. Some inherent problems are associated with this product regarding the energizing of the structure or the surrounding area from a lightning discharge. Any time the electrical potential of the tubing and any nearby conductive material are different, it is highly likely an electrical arc will occur between the two. When the arc is of sufficient energy, a hole can be burned through the thin tubing wall (approx .035). This arc can easily ignite the pressurized, flammable gas inside of the tubing as it escapes into the atmosphere. The escaping gas will continue to burn as long as the gas supply is not interrupted.
The installation of CSST is addressed in NFPA 54 (The National Fuel Gas Code) as well as in NFPA 70 (The National Electric Code). The electrical bonding and the isolation of the tubing are the accepted practices to guard against an electrical arc. Fire investigators and electrical engineers from Donan Engineering have teamed up to lobby for more stringent codes regarding CSST. Donan Engineering is an industry leader in the analysis of the failure mode regarding the involvement of CSST in fires.
Chimney Fires:
Solid-fuel-burning appliances—if improperly maintained or installed—are the cause of many residential fires each year. The majority of the solid-fuel-burning devices in residences are wood-burning units. A consideration for the investigator is how the unit is utilized. Many fireplaces are used sporadically and for aesthetic value. Other wood-burning units are used as primary heat sources for the structure. The maintenance of the unit and its initial installation are considerations that need thorough investigation.
Donan Engineering is routinely involved in assessment of the condition of wood-burning chimney systems. In recent years, homeowners have become much more aware of the need for proper cleaning and maintenance of wood-burning chimney systems. Certified chimney sweeps can assess the functionality of chimney systems. As more and more homeowners use chimney cleaning services, more chimneys are deemed “damaged by fire,” meaning that most insurance companies cover damage to any portion of the structure that is the result of a “hostile fire.”
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Many different types of approved wood-burning chimney systems are used. Masonry-constructed clay-tile-lined chimneys are very common units. When masonry clay-tile-lined chimneys are constructed, many times the expansion of the liner due to subjection to elevated temperatures is ignored, though this liner will expand each time it is heated. If insufficient clearance for liner expansion exists, the liner will most likely fracture when it expands. Unless these fractures are open and large enough to allow products of combustion to leak from the liner, they are only cosmetic in nature.
Numerous types of metal pipe are used for wood-burning fuel devices. Triple wall air-separated pipe, double wall air-separated pipe, and double wall-insulated pipe are frequently used. The biggest fire hazard with the use of metal chimney pipes is maintaining the proper clearance to combustible materials. Discoloration and severe oxidation of the interior of metal chimney pipe is the most easily recognizable evidence of excessive temperature.
If a chimney fire has occurred, some very distinct and recognizable evidence will remain. Chimney fires are the result of creosote build-up inside the chimney that is ignited by the heat of the exhaust gases; this causes the temperature inside the pipe to exceed the safe operating temperature rating of the pipe. During the chimney fire event, the burning creosote will be carried out of the top of the chimney. As the creosote exits the chimney and is cooled by atmospheric air, it will condense, and evidence of a brownish liquid will be present on the exterior of the chimney and inside the vent cap. If a chimney fire occurs, and fire is involving 15 to 20 feet of metal piping, the air influx at the wood burning device will be so intense that a roaring sound will be heard. Any person that has witnessed a chimney fire is quick to mention the noise associated with the event. Before damage to a chimney can be categorized as the direct result of a “hostile fire,” indicators must be evaluated. If no evidence of creosote deposits, report of a roaring sound, excessive evidence of oxidation on metal surfaces, or large fractures in clay tile liners are present, a hostile fire did not occur. If it cannot be determined that a hostile fire occurred, it is unlikely that any significant damage found in the chimney system is an insured loss.