Our DEI goals include but are not limited to ensuring that qualified AIHA Board candidates reflect the diversity of our membership. We believe that by drawing on the talents and skills of our members with different cultural backgrounds, our Board decisions will more accurately represent our members. We believe that an inclusive AIHA Board not only represents the realm of area of practice (that is, industry, academia, labor, and government) but also diversity in terms of race, ethnicity, gender, and thought across our membership. We will continue to seek candidates with the knowledge, skills, and abilities required to help advance and sustain the association so that our profession can better serve our diverse client base. Donna S. Heidel, CIH, FAIHA AIHA President

POST-FIRE EVALUATION The article “Analysis of Wildfire and Structure Fire Combustion Residues” (August) does not address a number of important considerations:

1. The article does not clearly define the overall (not just analytical) goal behind its proposed approach, which exclusively depends upon tape sampling and identification of combustion-related particulates by light microscopy as “the preferred combustion particle analysis procedure.” While the article specifically identifies “goals” of sampling and analysis of combustion residue as identifying impact from a site-specific source relative to background conditions, there are typically several other considerations associated with building damage due to post-fire residue or suitability for reoccupancy. Information regarding cause and origin of settled combustion particulates, however detected, is not necessarily determined exclusively through tape sampling and light microscopy analysis as implied by the article. This information alone cannot answer questions about damage to the building or when it is appropriate for the occupants to return.

2. The article focuses solely upon non-thermal damage in a structure (char, soot, and ash) in the narrow scope of settled particulate matter only. There are other manners of structural degradation that occur from the heat of adjacent and passing wildfire (thermal damage), and chemical contamination from products and devices that may have been consumed in the fire. Such contamination is properly characterized through particle counting and sizing, and chemical characterization (for which there are limited standards to define a target suite). AIHA’s Technical Guide for Wildfire Impact Assessments for the Occupational and Environmental Health and Safety Professional provides direction to include complementary volatile organic compound (VOC) and semi-volatile organic compound (SVOC) information, but this direction is not promoted in the article even though it is critical to a comprehensive evaluation.

3. The article does not provide any evidence that its narrowly prescribed combustion residue sampling and analysis approach has undergone standard verification or validation testing for repeatability and reproducibility. The article’s tape sampling/light microscopy approach is framed as preferable to the D6602 method, which the authors view as often “mistakenly cited . . . as a standard” for assessment of fire residues, due to its focus around carbon black. While D6602 may have some limitations when employed for post-wildfire or post-structural fire assessment, this is not a justification to disregard the standard in its entirety.

4. The article addresses much of the criticism of D6602 as a “wipe sampling technique” that establishes an inherent limitation due to potential altering of collected particles or their deposition pattern on surfaces. However, this criticism conflates the wipe sampling for transmission electron microscopy analysis (TEM) and tape sampling for light microscopy analysis, the latter of which is described in Section 6.3.2 of D6602. In so doing, the article frames D6602 as exclusively a wipe sampling/TEM protocol, which it is not. Generally, the article appears to arbitrarily discount applicable aspects and techniques for light microscopy analysis identified in D6602, and dismisses any potential meaningful information derived from electron microscopy analysis, to invalidate the use of D6602 in its entirety.

5. The article fails to discuss IESO-RIA 6001-2011, Evaluation of HVAC Interior Surfaces to Determine the Presence of Fire-related Particulate as a Result of a Fire in a Structure, which includes tape-lift sampling and light microscopy, as a parallel method for post-fire assessment. While the article states that its described tape sampling/light microscopy protocol is “preferred” as the “current industry-accepted methodology,” it provides no documented criteria in support of selecting this approach over others. Overall, the article fails to connect the sampling needs, desires, and uses with the analysis approach promoted.

The AIHA Real-Time Detection Systems Committee (RTDSC) has observed and appreciated the difficulties faced by victims of wildfires. We identified the complications of post-fire evaluation to the IH community of practice and brought them to the attention of the AIHA Board in July, which approved RTDSC member Dawn Bolstad-Johnson’s proposal to develop a more comprehensive post-wildfires evaluation document through AIHA’s Content Priorities Advisory Group. We hope this document will serve for the development of an ASTM standard and that the laboratory analytical community will join in that effort.

Respectfully submitted with endorsement of the full RTDSC membership.

ASTM D6602 is a widely recognized analytical standard that focuses on describing methods for the correct identification of the aciniform morphologies of carbon black and soot in addition to other common “darkening agents” present in environmental samples, like char, fly ash, rubber, and mold. The article claims that the ASTM standard is inappropriate because it is a wipe method, because it is not designed for analysis of fire combustion residues, and because it utilizes electron microscopy.

The AIHA Technical Guide describes three possible options for sampling—tape lifts, wipes, and microvacs—and the advantages and disadvantages of each. But the article instructs that only tape lifts should be used, a deviation from the Technical Guide, while citing the guide as a reference. The article adds to the confusion by referring to the D6602 standard as a “wipe-sampling” method. This assertion gives the impression that D6602 uses wipe samples exclusively. While the standard does require the collection of a wipe sample, it also requires, in section 6.3.2, the collection of a tape lift. The article recommends collection of samples via tape lift, so it is unclear why the authors fail to mention that the ASTM standard they criticize requires the same. As the ASTM standard states in section 7.3.2, “[t]he tape lift generally preserves the integrity of the particle aggregates without the smearing that tends to occur when using the wipe sampler.” This argument is also used in the article. In a tape lift, the fine particles are fixed in the adhesive of the tape, which provides the analyst with a representation of their spatial distribution; however, it also limits the analyst’s ability to interact with the particles. This is precisely why D6602 also requires the collection of a wipe sample, an approach that allows the analyst to extract and interact with representative particulate in the surface dust. Having side-by-side collected tape and wipe samples allows the analyst to investigate the full picture in a way that a tape lift alone or a wipe alone does not permit.

The article also states, “ASTM D6602-13 is intended only ‘for distinguishing ASTM type carbon black, in the N100 to N900 series, from other environmental particulates,’ as stated in section 1.1.” This is misleading. Section 4.1 of D6602 indicates, “This practice describes the procedures and protocols to follow in order to collect fugitive/environmental samples and identify the classes of particulate including materials consistent or inconsistent with manufactured carbon black” (emphasis added). The word “only” is not written in any section of the standard that indicates the scope. Nowhere in D6602 is there any suggestion that it should not be used for fire investigations or that practices described in the standard would cause “damage or remove many of the particles required to identify a wildfire or structural fire source” as indicated by the article. The section the article refers to, section 7.3.2, simply refers to smearing of particles during the collection of a wipe sample—which, again, is why the standard requires collection of both a tape lift and a wipe.

Although the article enumerates multiple limitations regarding the use of wipes, it fails to mention limitations introduced by tape lift sampling in general. These are addressed in the Technical Guide, which states, “rough surface finishes result in low removal efficiencies; extremely fine particles can be obscured by the tape adhesive/soot or other fine building or mineral debris; large agglomerations may not be accurately identified due to overlapping.”

D6602 also provides definitions for soot and char. Table 3 in section 7 gives an example of appropriate classes of particulate that can be reported during the optical microscopy of environmental samples: “pollen, fungal/mold/biofilm, soot (which may include aciniform carbon, fine char and carbon black), coal ash/fly ash, plant fragments, paint, insect parts, rust/metal flakes, rubber, coal/coke.” The standard discusses the benefits and drawbacks of sampling and analysis when tape lifts and wipes are used for environmental samples that contain soot and carbon black. It even provides microscopic images and elemental data for fireplace soot and wildfire soot. It is therefore unclear why the authors do not find this information applicable to projects investigating fire debris-containing soot.

The article states, “Some investigators and laboratories have mistakenly cited ASTM method D6602-13 . . . as a standard method for the analysis of wildfire and structure fire residues, which it is not.” This is a misleading statement. The applicability of D6602 to fire investigations is related to the correct identification of the fire combustion byproducts (including char and soot components) by PLM as well as characterization of the soot component in fire debris by TEM analysis, which the article fails to indicate. The standard mandates the use of the electron microscopy methodology for identification of aciniform morphologies such as soot because it is the only microscopic method with the magnification power to correctly assess the major fingerprinting parameters of these structures: the morphology, the aggregation patterns, the particle size range, and the elemental composition. It is a disservice to the scientific community to downplay the importance of applying the correct methodology to identify the presence, and in some cases the source, of the soot component in fire debris.

The article seems to suggest that the use of optical microscopy alone is enough for the identification of all components produced during wildfire or structure fire. The ASTM standard appreciates the importance of optical microscopy, and that is precisely why it describes an initial examination of both the tape lift and wipe with a stereo microscope followed by careful analysis of the tape lift and particles from the wipe using both reflected and transmitted light with a polarized light microscope. However, the article fails to mention that the ASTM standard it criticizes uses the same approaches the article recommends. But the ASTM standard does not stop with optical microscopy; it also incorporates the use of electron microscopy. The article fails to mention the main analytical limitation of optical microscopy: the lack of appropriate resolution to correctly characterize soot (or, in general, aciniform structures or structures with individual particles in the nanometer range). This is the important message that D6602 conveys to the scientific community, yet this message is concealed and somewhat dismissed by the article.

The article also states that “Electron microscopy (TEM and SEM) analyses cannot be directly compared with the quantitative estimates obtained by light microscopy analysis.” But quantitation by TEM or SEM alone is not the intent of this method. The ASTM standard requires quantification to be performed during the optical microscopy portion of the analysis and states in section 4.1 that “the TEM analysis alone cannot be used to estimate the amount of carbon black or other particle type in the whole sample.” It further states in section 8.1.1 that the TEM portion of the standard “is a mandatory evaluation of the aciniform materials present in the sample to determine primarily if their morphology is consistent with grape-like or branch-like structures typically associated with carbon black and soots.”

It is to be understood from the article that the only adequate sampling methodology for fires is tape lift, which is described as the “preferred” method, although it is unclear which industry segments prefer it. It is also to be understood that the analytical procedures discussed for the identification of fire debris components are tailored to be applicable for this type of sampling media. However, a bias is introduced when the reader is not informed about limitations of the proposed sampling and analytical procedures. Instead, the article presents and interprets in a limited fashion the information available in D6602, the only peer-reviewed standard that provides information regarding the correct identification of soot particles. It is most surprising that the article promotes the use of tape lifts and optical microscopy while at the same time attempting to discredit use of D6602, which incorporates both tape lifts and optical microscopy.

Disclosure: One of the authors of this letter is a member of ASTM committee D24 on Carbon Black and aided with the development of the D6602-13 standard.

THE AUTHORS RESPOND Many of the criticisms in the letters suggest that our article is somehow misleading or that it omitted items considered essential. Some detail was cut from our original submission to comply with the limitations imposed on a Synergist article. Those same limitations preclude us from publishing a full response in these pages. We strongly encourage practitioners in the industrial hygiene community to contact us and request a copy of our full response.

It is imperative that practitioners, IHs, and investigators do their own evaluation and make sure that laboratories meet the minimum criteria for optical microscopical requirements, analyst training, and reporting guidelines as outlined in the Technical Guide. Laboratories should encourage and recommend the use of tape lifts as the preferred collection method for evaluating char, ash, soot, and other signature particles, which are the primary indicators of wildfire debris impact as stated in the Technical Guide.

Most everyone can agree the consensus guideline is the Technical Guide, which was developed and peer-reviewed by over 20 wildfire experts including laboratory and field professionals. ASTM D6602 does not reflect or include the minimum requirements specified in the Technical Guide.

Below, we respond to the five items in the letter from the RTDSC: 1. Our intent was to provide a science-based approach to accurately analyze the optical properties of combustion particles characteristic of a wildfire or structure fire to accurately determine the source of the particulate. A laboratory is tasked with providing specific types of data to address specific concerns of the investigator. A laboratory then provides data to professionals with appropriate training, expertise, and context regarding a specific wildfire or structure fire assessment project. It is the investigator who makes decisions based on all site-specific data, not just the laboratory analysis aspects.

We agree with the letter’s statement that “Information regarding cause and origin of settled combustion particulates, however detected, is not necessarily determined exclusively through tape sampling and light microscopy analysis.” That said, tape lifts and light microscopical analysis is a well-documented and tested method of characterizing particulate to determine the cause and origin of particles on surfaces and has been used for that purpose at crime scenes since the 1800s. This method is used routinely to identify the source of environmental contaminants in aerospace, microelectronic, and other particle-sensitive industries. Other test methods begin with the assumption that the source is already known, which is a limiting assumption.

Both our article and the Technical Guide are in absolute agreement that tape lift samples are the preferred sampling method for evaluating char, ash, soot, and other signature particles, which are primary indicators of wildfire smoke impact. Preserving the relative position, density, depositional patterns, size, and shape of particles generated by wildfires (and structure fires) is necessary to establish a fire event-related impact, and to preserve the wildfire or structure fire “fingerprint.”

2. Our article was solely intended to focus on the analysis of solid particulate combustion residues and their impact to surfaces after a fire event. Complementary secondary methods such as VOC analysis or pH testing are often not recommended for post-wildfire particulate analysis because they are less reliable than optical microscopy. It is important to note that microscopical analysis relates to structure exposure only and is not a health assessment. If a structure has visible thermal damage, then other tests may be utilized. Microscopical analysis methods concentrate on establishing provenance (that is, source and history) of collected particulate in structures where the cause is not obvious. Hence, the assessment of wildfire and structure fire particulate matter in buildings is a straightforward trace-evidence investigation to establish provenance of the combustion residues and is best served by tape-lift sampling.

3. The letter misrepresents our article and the Technical Guide by not reviewing either publication in its entirety and by assuming our intent. Our article addresses deficiencies of both the tape-lift/optical and wipe/electron microscopy methods prescribed in D6602.

Simply put, there is no reason to use D6602 for the analysis of wildfire particles. D6602 is an appropriate method for the detection of carbon black, but it cannot identify the sources of soot. The sections of D6602 regarding analysis of other particulate by tape-lift sampling and PLM are rudimentary and quite insufficient for the analysis of wildfire particles. Proper characterization of char and ash require reflected darkfield illumination in addition to transmitted polarized light illumination. Surface morphology and overall structure are key to establishing provenance.

Particles collected using tape lifts may be quantified in several ways. Currently accepted methods include visual area estimation (VAE), which is well researched and validated. The VAE method was adapted from the asbestos industry (see EPA 600-93/R-116, Method for the Determination of Asbestos in Bulk Building Materials) but is widely used in a number of fields. While this is a reasonable solution, it is not the only solution. Current methods in use also include assemblage analysis, where the presence of specific indicators as an overall portion of the sample can help establish provenance and quantification. Counting and sizing methods are also used. All three variations are highly probative in nature, but it must be recognized that standardization of methods is ongoing as this application is a reasonably new field. Work continues to merge the three types into a complete industry standard that may exist as an ASTM method in the future. Unlike the use of D6602 for wildfires, we can show the probative value of our methods.

4. It must be noted that D6602 includes the use of TEM as an analytical tool for the identification of carbon black as its primary focus. TEM is well suited for this purpose—that is, the qualitative analysis of carbon black. It can confirm that there is soot present but cannot identify the sources of the soot. TEM is not suited for larger or thicker particles, and it cannot establish provenance of soot. One can only differentiate soot from carbon black, which is the main and correct use of D6602. To use this method for anything other than its stated purpose demonstrates a clear lack of appreciation for the analysis of environmental particles.

5. The letter argues, “While the authors state that their described tape sampling/light microscopy protocol is ‘preferred’ as the ‘current industry-accepted methodology,’ there are no documented criteria provided in support of selecting their approach over others.” This statement reflects misunderstanding of the Technical Guide, its consensus developmental history, and the IESO-RIA method the letter inaccurately claims we ignored.

The IESO-RIA document is the first industry-published method (in 2011) that even discussed the required use of dark-field reflected illumination as a standard microscopy analysis technique for structure fire combustion particles and tape-lift sampling as the primary sampling tool. The useful parts of this method were integrated into the Technical Guide over six years ago and did not need discussion in our article. The IESO-RIA method as written also falls short of providing the necessary minimum analysis requirements described in the Technical Guide.

While we appreciate the opinions expressed in the letter, it appears to discount the opinions, research, and worldwide scientific consensus field work presented in the Technical Guide. We quote directly from the Technical Guide: “Optical microscopy is the primary method used to identify wildfire combustion residues.” D6602 relegates optical microscopy to a minor, supportive role (as a screening test) to the prescribed “mandatory” evaluation by TEM. D6602 describes the light microscopy method as “useful” but “not mandatory and results obtained by this technique cannot be considered as conclusive for identifying the presence of carbon black.” This reversal of roles of analytical methodology is not just a concern of the importance and subsequent minimum technical requirements placed on both optical and electron microscopy methods, but also speaks to the priorities placed on analyst training and experience.

We wish great success to the RTDSC in its endeavors to quantify real-time detection of wildfire and structure products of combustion. We suggest that the committee consult with us and other members of the AIHA Wildfire Task Force, which drafted the Technical Guide, to ensure that the use of airborne microscopy methods, real-time particle analysis, and organic analysis are appropriately applied. Several other members of the Wildfire Task Force are also editors or technical contributors to the EPA bulk PLM asbestos method, the TEM water method, and the EPA airborne methods (AHERA), and have decades of experience with real-time VOC and laser-counting systems for evaluating airborne contaminants, time-of-flight laser analysis systems used for the direct real-time identification of short half-life combustion particles, and numerous other instrumentation suites. We look forward to hearing back from the RTDSC regarding this offer.