Fire Investigation Resources
Contact UsCase Study #1
This case study involved a mixed use structure with 30 stories. The fire appeared to have originated along the southwest side of the 26th floor of the building as evidences of fire damage observed there. These evidences include water damage observed on the ceiling and walls directly below the fire’s origin due to firefighting. Smoke appeared to have traveled throughout the 26th floor as visible smoke damage was observed on the walls and ceilings throughout the floor, along with fire debris sporadically on the floor. However, no evidence of fire damage was observed on the 27th floor or the 25th floor.
Concrete and masonry brick construction with plaster finish suspected to have served as a smoke barrier between the 26th floor and the 25th and 27th floors. With nowhere to go, the smoke from the fire likely traveled throughout the 26th floor with smoke probably traveled into the elevator shafts. Surface residues consistent with CBP contaminants were observed along the elevator doors on the 26th and 27th floor.
To determine if smoke had traveled beyond 26th floor, the inspector collected some surface samples from the 25th floor and the 27th floor, and even from the 30th floor elevator door. Of the eight samples collected from the fire incident, seven of them found to contain CBP concentrations from greater than 1% to 10%.
The results indicate that CBP contaminants were carried throughout the 26th floor. The results further indicate that smoke traveled to the 27th floor via the elevator shaft as CBP contaminants were detected along the exterior wall and the hallway outside of the elevator on the 27th floor. The results also suggested that smoke traveled to the 25th floor as CBP contaminants were found along the exterior wall and outside of the elevator on the 25th floor. In fact, CBP contaminants were detected in the elevator shaft as far as the 30th floor.
Based on the sampling results and visual observations, the inspector recommended removing smoke damaged porous materials and thoroughly clean hard surfaces on the 26th floor. He also recommended cleaning of elevator shafts from the 25th floor to the 30th floor.
Case Study #2
This case study involved a 3-story hotel building. The hotel claimed that ongoing smoke odor was the result of insufficient professional smoke restoration following a wildfire event in the vicinity of the hotel one year prior.
Before the cleanup of the combustion-by-products from the wildfire, project oversite and work practices were approved by both the hotel and the remediation company, but no post cleaning verification was performed by either party. Approximately one year later, the hotel management received some complaints from guests that their rooms had smoke odor, so a consultant was brought in to investigate if any remnant wildfire CBP residues were present in the hotel. However, the consultant did not find any interior space smelled of smoke odor from the wildfire. Instead, the investigation discovered an alternate smoke odor source coming from nearby restaurants using fire-burning cooking appliances.
To prove that no wildfire damage residual was in the hotel, the inspector collected 11 surface samples from various rooms where complaints were made for combustion by products testing. All samples had none detected or <1% for soot, char, and ash. The inspector requested further analysis on the collected samples using the forensic approach called assemblage analysis. Instead of arriving at a conclusion based on a single component of the assemblage, this analysis uses multiple pieces of information from the sample. The typical wildfire assemblage may include charred wood, fire retardant, burned soil, carbon coated mineral grains, and phytoliths. The lab results did not support the presence of wildfire residual in the building.
What can we learn from this case study? CBP analysis by remediation contractor at the completion of a job could have provided clearance to avoid unsubstantiated claim of incomplete cleanup. If you are a remediation contractor, keep in mind that post remediation testing could be a good way to avoid future liability.
- What is the benefit of a corrosivity test for wipe samples?
Fire residuals are rich in cations and/or anions and therefore can be corrosive. Wildfire residuals tend to be alkaline (pH varies from ~ 9 to 14) due to the presence of cations such as Ca, Mg, K, etc. In the contrary, structure fire residuals tend to be acidic (~ 3 – 6) due to the presence of anions such as Cl, S, P, F, etc. Corrosivity testing results can be used by consultants or remediation contractors to determine if items in a fire impacted building need to be cleaned and/or disposed with or without the presence of elevated combustion-by-product particulates as corrosive residuals can damage many household items such as electronic devices, leather furniture, and carpeting, etc.
- Is licensing or certification required for combustion-by-product sampling and analysis?
The simple answer is no. Sampling and analysis for combustion-by-products is an emerging field, and there are currently no government regulations or certifications for either sampling or analysis, although training for fire damage inspection by private institutions or organizations is available. Presently, there is no accreditation program exist for laboratory testing for combustion-by-products.
- Can the debris rating be used to infer general risk to health to occupants, or can it be used to infer past airborne combustion byproduct concentrations?
Debris rating is used to describe the levels of surface area obscured by particulates on a sampled surface under light microscopy, and it is not directly related to health or past airborne combustion-by-product concentrations, although the same CBP concentration with higher debris rating may indicate more severe CBP contaminations.
- Where would control samples be taken from?
Because there are no regulations or standards for combustion-by-products testing, we recommend control samples be taken for comparison. The best control samples should be taken from an area where it has not been impacted by fire damage. In the case of wildfire damage, this may be very difficult to do due to typically the large scale impact of wildfires.
- Can you provide a general template of what a combustion by-product report would look like?
Certainly. We have sample reports for different CBP testing services or combination of testing services, such as by PLM/RLM, PLM/RLM with TEM soot confirmation, etc. Please contact our offices for a copy of the sample reports.
- In reporting, does ND represent <1% or a debris loading of 1? Or is ND a complete absence of observed combustion by products?
Combustion-by-product particulates testing is performed using microscopy technique, and therefore ND means no CBP particles are detected. The concentrations are reported based on calibrated visual estimate methodology, and the reporting limit of the method is 1%. Therefore, <1% means presence of CBP particulates at a concentration below the reporting limit.
- Regarding testing following fire restoration, what are acceptable levels of CBPs? Is the goal zero (%) for soot, char or ash?
CBP can be caused by many household activities and in nature, and therefore, is present in the background. This background level is a function of many factors and varies from area to area and from urban environment to rural settings. Based on our experiences, the typical urban area has a CBP concentrations of <1% - 2%. The level is expected to be higher in the rural area where intentional burning of biomass occurs or wildfire impacted area. So if the goal of the fire damage restoration is to restore the living environment to the pre-fire damage condition, zero goal may not be necessary.
- Your thoughts regarding scented candles in homes. Is discharge considered diminimus?
This question is hard to answer. It depends on if the occupants are sensitive to the chemicals and soot particles released during the candle burning and how much of the product is used. In general, it shouldn’t be a big concern if small quantity is used for a short duration. However, there are cases in homes where soot ghosting has occurred due to long term usage of large quantities of candles.
- Can you differentiate between background CBP and fire CBP - for example cigarette/ fireplace/ candle CBP?
Assemblage analysis, which is a forensic microscopic approach, is often used to differentiate background CBP and wildfire CBP. Instead of arriving at a conclusion based on a single component of the assemblage, it uses multiple pieces of information from the sample. The typical wildfire assemblage may include charred wood, fire retardant, burned soil, carbon coated mineral grains, and phytoliths. Chemical testing and morphological features can sometimes differentiate fire related CBP from background CBP, but a reference material may be required.
- Can incomplete combustion of natural gas/propane result in soot deposition simply because of inefficient combustion, such as would be the result of flickering?
The simple answer is yes. When incomplete combustion of natural gas/propane at your furnace, soot and carbon monoxide are generated and released into the air. Soot particles are very small and can be suspended in the air for a long time. It can also be adsorbed on surfaces due to thermophoresis and electrophoresis.