Comparable Aspects of Forensic Fire and Water Investigations

Introduction

In January 2015, a major fire destroyed roofing and attic spaces (Photo 1) and top floor apartments (Photo 2) at an historic three-story, wood-framed, mixed-used building in San Francisco’s Mission District. The fire alarm system failed to activate – one tenant lost his life as attic fire and smoke dropped down into occupied third-floor apartments.

A San Francisco Fire Department investigative team promptly carried out an ‘origin and cause’ analysis of the fire. Per the SFFD’s Fire Investigation Report, the teams’ method of examining the fire scene followed the guidance of industry standard NFPA 921 (Guide for Fire and Explosion Investigation) published by the National Fire Protection Association.

Eighteen months later, AVELAR was asked to evaluate this SFFD Report and supporting digital photographs to judge whether or not the team’s forensic (puzzle-solving) process and findings were consistent with NFPA 921.

Our close assessment of NFPA 921 demonstrated that key aspects of the physics of flame spread in a building are comparable (but often inverted) to that of liquid water. While water leakage commonly migrates downward (due to the effects of gravity) and laterally from a source of leakage, fires tend (with certain exceptions) to spread upward and outward from their origin points. Hot gases and airborne products of the combustion process are expansive and less dense than the surrounding air — this growth in volume and buoyancy causes fire plumes to rise and spread.

As a result, the lowest portion of a fire pattern often is closest to the fire’s ignition point. In like manner, water leakage investigators commonly search upward for leakage sources. A common objective of both fire and water scene examinations is analysis of damage patterns to identify origin points. While fire investigators commonly move from least-burned to most-burned areas, water leakage sleuths often (but not always) begin at areas of severe decay and deterioration and then search toward drier, less-damaged materials.

The authors of NFPA 921 delineate critical steps in its “scientific method” of fire investigation: i) collect data; ii) analyze this data (via “inductive reasoning” ) to form a preliminary hypothesis; and iii) test this hypothesis via “deductive reasoning”.

These steps are repeated as necessary to develop a final hypothesis that both matches the observed facts and is fully consistent with fire science.

• The inductive reasoning process produces a preliminary premise from specific observations and data. Then, the investigator deductively challenges this hypothesis with additional facts and relevant theory.
• Similarly, a skilled leakage investigator’s forensic process commonly is both inductive and deductive and will be carried out with methodological competence, intellectual rigor and professional integrity.

This report follows the SFFD team members (led by Fire Investigator Stephen Engler) as they searched for a “uniquely consistent” hypothesis that best explained the origin and cause of this deadly fire.

Photo 1 – The fire spread rapidly through the open attic space and then “dropped down” (per Photo 2) into apartments below.

Photo 2 – Because the fire alarm system failed to activate, some third-floor tenants were found still in their rooms with smoke filling their units from the ceilings down. The fire was first observed at the ceiling of the closet seen in this photograph.

The Effects of Missing Fireblocking and Attic Draftstopping

Our post-fire inspection of this circa-1907 building confirmed that the absence of fire blocking and attic draftstopping contributed to the rapid spread and severity of this fire (which ‘dropped down’ from the open attic into occupied apartments below).

• As evidenced by Photos 3 and 4, NFPA 921 well summarizes the potentially severe effects of diminished fire-blocking: “Where such fire stops were not installed …unobstructed vertical channels, in concealed spaces behind interior finish, …will also allow fall down from above to ignite lower levels and allow combustion gases, trapped inside higher elevations, to push or convect downward through the open vertical channels. Fire originating on lower levels can extend into the open vertical channels and may break out in one or more floors above where the fire originated. There can be more extensive burning at the upper level than where the fire originated. This result may be recognized by the attic fire that consumes the top of the structure while the fire actually originated at some lower level.”

Photo 3 – Due to absent blocking, the fire dropped down from the attic into this wall cavity.

Photo 4 – Due to absent fireblocking at ceiling-to-wall transitions (at the bottom of the joists), the spreading fire also dropped down into multiple apartments via open stud bays.

Initial Eye Witnesses to the Fire

The fire was first observed about 6:00 pm on January 28, 2015 by a tenant in the south-facing apartment shown in Photo 2. He told the SFFD investigators that: “He was in the kitchen at the sink washing his lunch box from work. He said he went to the bathroom and as he walked past the closet door in the hallway, he saw a ‘glow’ coming from within the closed closet door. He stated he opened the east closet door and saw fire near ‘from the floor up’ in the closet.” The frightened tenant (whose wife and child were at a nearby store buying food for dinner) then pounded on his neighbor’s door to warn them of the fire and to call 911.

An emergency rescue vehicle was the first SFFD unit to arrive. This crew saw “high fire” at the east elevation and found “third-floor occupants still in their rooms with smoke filling the units from the ceiling down.” At the northeast corner of the building (at the 3^rd floor) they found the body of a tenant who had succumbed to this smoke. Their resuscitation efforts were not successful.

An SFFD fire engine also arrived at the south elevation. As evidenced by the smoke damage seen in Photo 5, these firefighters “saw flames coming from a third-floor window near the center of the building.” Upon advancing to the apartment seen in Photo 2, this crew found the unit “fully involved” in fire. They extinguished the immediate fire in this apartment and then were assisted by “additional fire crews in exposing a large volume of fire in the attic space above”.

At 6:50 pm, SFFD’s “fire investigative unit was automatically dispatched to the second alarm fire.” As this conflagration eventually progressed “to a four-alarm fire, and defensive fire tactics were deployed”, these investigators already had commenced their “origin and cause” analysis. The team’s first digital photograph has a time stamp of 7:11 pm. They worked until after 2:00 am (when “fire suppression companies resumed an aggressive fire attack to extinguish the fire throughout the attic space of the building”) and then returned to the smoldering building at 8:00 am to continue their forensic analysis.

The SFFD Fire Investigators’ Puzzle-Solving Process

Consistent with industry standard NFPA 921, when the investigators returned in the morning, they started their forensic documentation and analysis at least-burned areas (including the east-facing apartment where the tenant had succumbed to smoke inhalation) and eventually proceeded to south-facing unit (Photos 2, 4 and 5) where the fire reportedly had first been observed within the closet next to the kitchen. (Upon reviewing their Report, it seems clear that these investigators initially hypothesized that the fire had originated within this apartment.)

Photo 5 – Firefighters “saw flames coming from a third-floor window near the center of the building” at the same apartment seen in Photo 2.

Photo 6 – A view (facing south) of the partially collapsed roof/attic space atop the third-floor apartment seen in Photo 5. (Note that SFFD firefighters cut a large opening in the roof to vent the fire.)

It also is clear that any such preliminary hypothesis would constitute a good example of the recommended “inductive reasoning” process intended by NFPA 921 to produce preliminary premises from specific facts. At this point in time, the SFFD team still believed that this closet and the adjoining kitchen were the lowest area of heavy fire damage within the most-severely damaged apartment on the third floor. Further, occupied residences (kitchens in particular) can be expected to contain many potential fire-ignition sources.

The SFFD team searched the entire apartment for evidence that would confirm, via “deductive reasoning”, this preliminary hypothesis. Specifically, the investigators looked for an “ignition device” that could have initiated (caused) the fire. However, their search was fruitless.

Unburnt clothing and materials (including candles) at the closet floor indicated that the fire did not start there. Inspection of the closet’s light switch and associated wiring found no evidence of an electrical fault. All of their observations within this closet (and also the adjacent living and sleeping rooms) were consistent with the effects of a “drop down” fire from the attic above.

The SFFD team then continued into the kitchen:

• “We inspected the motor area and electrical connection to the refrigerator… [which] appeared intact and uninvolved in the ignition sequence of the fire. We located an electrical plug-strip supplying power to the refrigerator.  The plug-strip appeared intact and uninvolved on the ignition of the fire.”
• “In this west area of the kitchen we located stranded electrical wiring some of which led to an uninvolved and intact toaster oven.”
• “We located and inspected a steel microwave oven… We noted extreme fire damage to all exterior sides of the microwave oven. The wiring and motor area of the microwave appeared intact.”
• “In this north/east area of the kitchen we noted a cook/top oven placed against the east kitchen wall. We noted the interior oven area of the oven was free of damage… We eliminated a heating event inside the oven as a cause of the fire.”
• “We noted heat damage to the exterior sides of the oven with protected area near the east corners.  …We inspected the area beneath the cook-top and noted this area appeared intact and free of damage.”
• “We noted areas of the east wall behind the stove had been consumed by fire. Above this area, we noted the ceiling joists with less burn damage to the bottom surfaces and increasing damage to the top surface to areas of the attic system indicating severe fire involvement in the area above the kitchen.”

In short, the investigators found: i) no evidence of a fire-ignition source anywhere in the kitchen (including within, behind or below the gas-fired ‘cook/top oven’); and ii) further evidence of an attic fire that had dropped into both the living room closet and the adjacent kitchen due to missing fireblocking, as seen in Photo 4.

• Per NFPA 921, absent any factual evidence of any ignition source, any origin and cause determination by any party at this point in the SFFD investigation would have constituted improper speculation.

The SFFD Team Expands its Search for Hard Evidence of an Ignition Source

The SFFD investigators departed the site on January 29 without finding evidence of any likely ignition device. They returned on February 13, 2015 to expand their search. Within a short period, the team had narrowed its focus to the southwest intersection (about 50 feet from the fire-damaged unit depicted in Photos 2, 4 and 5) of the third-floor hallways.

As seen in following Photos, the investigators removed additional plasterboard at this hallway corner to further expose a steel-encased electrical enclosure (positioned directly below a vertical lightwell shaft bringing natural light down from the roof to the bathroom window of the adjoining apartment) that housed a wide variety of electrical panels, boxes, conduits, and wiring: some dating to original construction circa-1907; others associated with circa-1978 rewiring work replacing the original knob-and-tube system; and yet other equipment that had housed and serviced a cable television “port distribution amplifier”.

The SFFD team later reported:

• “We continued our examination of the third floor to a burn pattern that was located in the third floor south/west hallway within the west stud wall. We noted a directional burn pattern within this wall originating in the area of two electrical panels with fire extension and progression extending vertically up the stud channel to, and through the top plate of the wall into the attic space above.”
• “We exposed the plaster and lath in this area of the wall and noted the bottom plate of this stud channel appeared free of fire damage.  We noted directional burn patterns …with heat oxidation to the back sides of the electrical panels with heat and fire damage indicating fire progression from the lower electrical panel vertically up the stud-channel.”
• “Within this area, we located an area of extreme fire involvement. We noted the burnt framing of suitcases, the steel radial remains from automotive tires, and a large quantity of burnt stored materials.  We located …two fire-involved electrical panels within the west wall of the storage area. In the lower panel, we noted the remains of a ‘Port Distribution Amplifier’ and cordage that was extremely fire damaged. We noted …interior areas of the electrical box containing areas of extreme fire involvement.”
• “We noted this area within the third floor south/west hallway within the west stud wall to be the lowest point of burn damage within the structure. We noted communication of fire damage to and throughout the common attic space above.”

Ibid., Section 28.8: “The objective of every origin and cause investigation is to establish the cause of the fire and to confirm this finding by identifying and, if possible, recovering the heat source or ignition device.”

Ibid., Section 4.1: “With few exceptions, the proper methodology for a fire or explosion investigation is to first determine and establish the origin(s), then investigate the cause: circumstances, conditions, or agencies that brought the ignition source, fuel, and oxidant together.”

Ibid., Section 19.6.5: “Any hypotheses formulated for the causal factors (e.g., first fuel, ignition source, and ignition sequence), must be based on the analysis of facts. Those facts are derived from evidence, observations, calculations, experiments, and the laws of science. Speculative information cannot be included in the analysis.”

The purpose of a “port distribution amplifier” is to increase the strength and quality of received signals to levels that are greater than the signal losses associated with lengthy distribution systems.

Photo 7 – The SFFD team concluded that an intense fire originating within this steel-encased electrical enclosure had then migrated up the fire-destroyed stud bay (at left) into the ceiling (see Photo 18) – where it then spread throughout the open attic dating to 1907.

Photo 8 – During original construction (circa 1907), this steel-framed electrical enclosure had been encased with steel plating.

Photo 9 – Overlapped steel plates were nailed (no rivets) thru the wood board sheathing into the now-missing wood stud.

Photo 10 – Fire and intense conductive heat (through the steel plating) had consumed the wood board sheathing and stud.

Photo 11 – “Electrical panel” opposite the fire-damaged wall seen in Photos 8 and 9 was moved by Fire Investigator Engler. (Materials that had been stored within this electrical enclosure included suitcases, tires, and paint cans.)

Photo 12 – When the “electrical panel” was moved, the steel plate sprung inward (because it no longer was nailed to the stud).

Photo 13 – When the “electrical panel” was moved, the steel plate sprung inward (because it no longer was nailed to the stud). (SFFD: “We noted the remains of a ‘Port Distribution Amplifier’ and cordage that was extremely fire damaged.”)

Photo 14 – Fire and intense conductive heat (through the steel plating) melted the fiberglass bath in the adjoining bathroom. (Note: no fire damage was found within the lined lightwell located above the fire-ravaged, steel-encased electrical enclosure.)

Photo 15 – While steel plating (at the electrical enclosure) and remnants of this bathroom wall’s original plasterboard can be seen behind the melted fiberglass, the wood stud framing behind this plasterboard was totally destroyed by the intense heat.

Photo 16– The wood stud framing under the melted fiberglass was totally destroyed by the intense heat.

Photo 17 – The wood stud framing under the melted fiberglass was destroyed by the intense heat.

Photo 18 – The fire progressed up the unblocked stud bay at left (see Photo 7) encasing the vertical piping and then spread laterally into the open attic seen in Photo 1. (Note, at right, electrical conduit installed in 1978 to replace the original knob-and-tube wiring system.)

The evidence (per Photos 9 thru 13) relied upon by the SFFD investigative team is consistent with the guidance of NFPA 921:

• “Contained within the specific origin area will be the precise location where the ignition source came into contact with the material first ignited and sustained combustion occurred. Physical evidence of the actual ignition source is likely to be located at or within close proximity to the point of origin.”

Further, as evidenced by Photos 14 thru 17, the team also determined that the fire within this electrical enclosure had been so intense that heat transference (thermal conductance) through the steel plating had melted fiberglass panels at the bathtub and shower at the adjoining apartment.

• “Conduction is also a mechanism of fire spread. Heat conducted through a wall or along a pipe or beam can cause ignition of combustibles in contact with the heated object. Thermally thin materials are those materials that are physically thin or have a very high thermal conductivity.”
• Note in these photograph that while steel plating and remnants of the wall’s original plasterboard can be seen behind the melted fiberglass, the wood studs sandwiched between the plasterboard and steel plating were totally destroyed.

• Also, note in Photos 14 and 15 the sill of the wood-framed window that was served by the vertical lightwell atop this steel-encased (and steel-framed) electrical enclosure: the SFFD team opened this window and found no fire involvement within this lined (i.e., fire-protected) shaft.

The SFFD Team’s Final Hypothesis of Origin and Cause

In its final Report, the SFFD team advises:

• “At the conclusion of our investigation we were unable to eliminate an unspecified electrical fault or failure involving this ‘Port Distribution Amplifier’ with vertical fire extension up the south/west hallway within the stud wall, through the top plate and throughout the common attic as the cause of the fire.”
• “Extreme fire damage throughout the common attic space indicated fire progression from this south/west area of the third floor throughout the attic space with initial fire presentation as ‘drop down’ of burning material to the closet space and kitchen of [the south-facing apartment in Photos 2, 4 and 5].”

As noted, our firm’s assignment was to assess the overall quality of the SFFD investigators’ forensic process. To that end, during a twelve-month period, we: inspected the building (which has since been demolished), reviewed all reports, documents, and photographs produced by SFFD, examined all historical permit records archived by San Francisco’s Department of Building Inspection, scrutinized the many thousands of photographs taken by other consultants, consulted fire and electrical engineering professionals, and closely considered the guidance of industry standard NFPA 921.

This extensive assessment confirmed that: i) SFFD Fire Investigator Engler and his team members followed NFPA industry standards; ii) and their final ‘origin and cause’ hypothesis is wholly consistent with observed conditions, available facts and photographs, and the basic principles of fire science and forensic evaluation outlined in NFPA 921.

Further, as supplemented by our inspection at the building before it was demolished, a close review of the SFFD team’s digital photographs (in particular, Photos 7 and 18) also confirmed that the initial “vertical fire extension …within the stud wall” was facilitated by the absence of fireblocking at the vertical water piping that was teed from the larger horizontal piping run seen in Photo 18.

In short, SFFD’s photographs and overall evaluation process well demonstrate their final hypothesis that this fatal fire started at the ‘port distribution amplifier’ (Photo 13) within the steel-encased electrical enclosure (which was filled with highly flammable materials, per Photo 11), then “progressed” up into the stud cavity seen in Photo 7, then spread laterally into the open attic (Photo 18), where it then dropped down into occupied apartments via numerous unblocked stud cavities (Photo 4).

Our firm’s only additions to this well-reasoned analysis are to note that:

• The fire’s initial spread up the wall was facilitated by the failure to install fireblocking around the steel piping seen in Photos 7 and 18.
• The fire’s spread from this steel-encased electrical enclosure likely was facilitated by an opening that was created between the two overlapped steel sheets (which had been nailed to the now-missing wood stud, per Photo 9) when this wood stud and underlying sheathing boards were consumed by heat and fire. The loss of this structural support allowed the two steel sheets to separate (Photos 12 and 13), thereby creating a gap that allowed the fire to continue to spread into the stud bay seen at Photo 10.

Consideration of Alternative Hypotheses

Whether related to fire or water damage, all forensic investigators should consider the potential merits of any alternative hypothesis that fits all of the facts and the principles of fire or water science. While it certainly is not uncommon within a litigation process to come across seemingly odd theories offered by advocate consultants, these alternative perspectives still should be strained through an analytical sieve crafted from facts and logic.

While the SFFD team members found no evidence to support any other likely explanation for the origin and cause of the fire, they certainly never ruled out the possibility of a credible alternative theory being offered by other parties.

One alternate theory proffered by certain parties was that the fire actually originated (perhaps due to an alleged cooking error by the tenants) in the south-facing apartment seen in Photo 2 and then migrated up into, and then spread throughout, the open attic — where it then dropped down into various other apartments and spaces, including the unblocked stud bay seen in Photos 7 and 18, where it then consumed the now-missing wood stud and associated sheathing boards and then migrated in the adjacent stud bay (at Photo 10) while also infiltrating the steel-encased electrical enclosure to ignite the very intense fire that melted the fiberglass panel in the adjacent bathroom.

• In essence, these parties asserted that it was just a coincidence that the fire-scarred steel-encased electrical enclosure at Photo 9 and the stud bay at Photo 10 are the lowest point of fire damage in the building.

Upon review, this hypothesis appears to be directly contradicted by fire science, as summarized and detailed in NFPA 921.

• For example, consider the “fire pattern” of rising damage seen in Photo 7 as “the hot gases created by the fire rise above the fire source as a fire plume” and then, at the ceiling, move horizontally as a “ceiling jet”, as evidenced by Photo 18.
• In contrast, there appear to be no scientific principles within this comprehensive NFPA 921 standard that would substantively support any alternate hypothesis that the fire instead spread downward into this wall cavity (but not all the way to the bottom), then selectively consumed one missing stud while migrating into the adjacent stud bay (creating the lowest point of fire damage, per Photo 10), and then incidentally happened to ignite the intense fire within the steel-encased electrical enclosure that melted the fiberglass panel in the adjacent bathroom while similarly consuming the “port distribution amplifier” in Photo 13.

Further, the lack of any substantive evidence to support this speculative alternate theory would be sufficient to render it invalid: for example, when the SFFD team members inspected this apartment on the day of the fire, and then closely reexamined the entire unit on the following day, they found no indication of any cooking activities by the tenants immediately prior to the fire.

• The authors of NFPA 921 provide the following perceptive guidance that is valid for both fire and water investigations: “Any hypothesis that is incapable of being tested either physically or analytically is an invalid hypothesis. …The inability to refute a hypothesis does not mean that the hypothesis is true.”

Comparable Aspects of Fire and Water Investigations

NFPA 921-14 is a highly instructive 401-page standard that prescribes: “The systematic pursuit of knowledge involving the recognition and definition of a problem; the collection of data through observation and experimentation; analysis of the data; the formulation, evaluation and testing of a hypothesis; and, when possible, the selection of a final hypothesis.”

These basic principles of ‘origin and cause’ evaluation are closely comparable to the cognitive process of water leakage evaluation summarized within industry standard ASTM E2128: “The sequence of activities is intended to lead to an accumulation of information in an orderly and efficient manner, so that each step enhances and supplements the information gathered in the preceding step. …The evaluation of water leakage of building walls is a cognitive process in which technically valid conclusions are reached by the application of knowledge, experience and a rational methodology…”

It is clear that the fundamental underpinnings and requirements for valid fire and water forensic investigations are comparable: “These hypotheses should be based solely on the empirical data that the investigator has collected through observation and then developed into explanations for the event, which are based upon the investigator’s knowledge, training, experience, and expertise.” The SFFD team members (in particular, Fire Investigator Stephen Engler) should be commended for their adherence to this guidance.

For all such forensic evaluations, the best investigative methods tend to produce the most credible and valid findings. To this end, the authors of the closely comparable puzzle-solving methodologies delineated within industry standards NFPA 921 and ASTM E2128 would eschew the practices of any fire or water consultant “whose narrow focus in litigation cases simply is to mine the database only for information that advocates their predetermined position.”

This perspective should not be construed as a blanket rejection of origin and cause hypotheses that may differ from that produced by the SFFD investigative team. Instead, because this SFFD analysis appears to be so consistent and credible, it simply is important to emphasize that proponents of any alternative theory also need to present a similarly credible analysis based on facts derived from evidence, observations, calculations, and the laws of science – without any reliance on speculation.

Those consultants who specialize in forensic water leakage investigations will recognize the closely comparable aspects of forensic fire investigations. An investigator’s inductive reasoning process first produces a preliminary premise from specific observations and data; then, he/she deductively challenges this hypothesis with additional facts and relevant theory. This skilled forensic process, which is carried out with methodological competence, intellectual rigor and professional integrity, commonly will be repeated until a uniquely consistent hypothesis explains the origin and cause of the water leakage (or the fire).