11:58:59 From Don Weekes : Ten years.
11:59:19 From Don Weekes : The countdown is one!
12:00:18 From Don Weekes : I agree with Derrick that in-person conference are much better.
12:03:30 From cliff zlotnik : was the confidential codename assigned to the preparations or the DDay invasion?
12:03:40 From John Lapotaire : Operation Overlord
12:03:51 From cliff zlotnik : sorry incorrect
12:04:41 From John Lapotaire : Neptune
12:05:07 From cliff zlotnik : sorry incorrect
12:05:44 From ralphsmacbook : bolero
12:05:55 From cliff zlotnik : sorry incorrect
12:05:59 From John Lapotaire : Operation Fortitude
12:06:17 From cliff zlotnik : sorry incorrect
12:06:28 From John Lapotaire : Damn it.
12:07:03 From ralphsmacbook : ceremony
12:07:12 From cliff zlotnik : sorry incorrect
12:07:44 From ralphsmacbook : game
12:08:05 From cliff zlotnik : sorry
12:08:39 From ralphsmacbook : attack
12:08:45 From John Lapotaire : Bodyguard
12:09:00 From cliff zlotnik : sorry still incorect
12:09:08 From ralphsmacbook : kit
12:09:24 From cliff zlotnik : sorry
12:09:30 From ralphsmacbook : youtube
12:09:57 From Bruce : Thunder???
12:10:10 From John Lapotaire : Dragoon
12:10:22 From ralphsmacbook : chicago
12:10:28 From cliff zlotnik : sorry
12:10:41 From Don Weekes : COSSAC
12:11:14 From cliff zlotnik : sorry
12:11:14 From John Lapotaire : Gotta get back to it.
12:17:04 From Don Weekes : Operation Tiger
12:17:39 From cliff zlotnik : sorry
12:19:19 From Don Weekes : https://totalmilitaryinsight.com/codena ... ith-d-day/
12:21:43 From cliff zlotnik : The answer we were looking for is BIGOT
12:23:46 From Bruce : Everyone addresses, when sampling for Char/Soot/Ash. identifying ID and extent. What about after remediation, how does the "owner" know the work is completed accurately? Visual? Resampling? Wipes? Tapes?
12:24:10 From Don Weekes : One of the issues with sampling is: Who should be the individual who collects the sample? Is it someone with a certificate or a certification?
12:29:20 From Don Weekes : A well-trained monkey.
I do agree that sample results should be intrepeted by a certified individual.12:34:06 From Don Weekes : Both Cliff and I have 50 years of work experience. BUT: Our expertise is totally different. I wouldn't know restoration like he does, and I believe that I may have more expertise on sampling and lab results, particularly intreperation.
12:36:20 From cliff zlotnik : No disagreement with me Don.
12:42:44 From Don Weekes : With wildfires, it is individual risk versus community risk can be quite different. The individual may be at higher risk due to preconditions such as medical conditions. The community risk can be quite different, as shown over and over with wildfires.
12:47:59 From Don Weekes : For example, their is an air quality advisory today in Ottawa (and elsewhere in Canada). For the elderly, this is an important risk to them. But for most residents, this is more a visual conditions with smoke in the air.
12:50:52 From Thomas Martin III, PhD’s iPhone : Here in Florida at a resort restaurant close to me the cooks complain about VOCs to local government and they send in Fire Dept to inspect for gas..
#indoorenvironmenteducation
13:03:24 From Don Weekes : https://evreporter.com/dealing-with-lit ... 20property.
13:04:15 From Don Weekes : https://www.dhses.ny.gov/system/files/d ... /h_m20.pdf
13:05:54 From Don Weekes : https://www.usfa.fema.gov/a-z/lithium-i ... trategies/
13:07:16 From ralphsmacbook : What about other battery chemistry hazards?
The article I provided comparing the two techniques illustrates why using soot, char and ash analysis can create both false positives and false negatives.
The chart I previously sent, excerpted from the study, shows the findings from the study and the misclassification that results. Here are some key elements of why soot counting is bad science, or at least it will get you in trouble if you are in court attempting to defend it against assemblage analysis.
"Combustion products are not the only black particles in an environment. Tire wear, shoe wear, fretting metal wear, dark minerals, insect debris, fungal debris, decayed plant material, insect and arachnid frass (see Photograph 4), newspaper ink, toner, cosmetics, pencil debris, etc. are always or often black and are not uncommon in indoor environments. The products of combustion are not all black or even dark. When all of the carbon is consumed the result is generally a white, yellow, or red ash. These particles still retain structure and optical characteristics sufficient to be identified as ash if they are carefully lifted from a surface (see Photographs 5 and 6).
Photograph 4: Gnat Fecal Pellet (Frass)
This is frass from a mold eating Gnat on a tapelift from an attic.
Photograph 5: White Ash with Cell Structure
This type of fragile particle is destroyed when a wipe or vacuum sample is taken. This particle is white with reflected light.
Wildfire Smoke Exposure: A Comparative Study
6
The identification of these materials requires a mount of high optical quality. That is not possible with a tapelift unless the plastic backing is removed. The plastic backing is too stiff to conform to particles thicker than about three quarters of the adhesive film thickness. The adhesive film is typically ten to twenty micrometers thick (0.01 to 0.02 millimeters). As a result, particles thicker than about seven micrometers (0.007 millimeters) are often associated with pockets of air that mask their morphology and their optical properties. If the plastic film is removed without significantly disrupting the particles in the adhesive layer then the adhesive will conform to the particles and no optical gaps will be present. With the clear tapes used for SC&A analysis the plastic backing cannot be removed without serious disruption of the particles in the adhesive layer. A tape commonly used when a detailed analysis of surface dust is required is 3M Scotch Brand frosted Magic Tape."
"The proper identification of dark particles becomes very difficult. Tire debris, dark minerals, cenospheres, magnetite spheres, and many other interfering particles can be misidentified as char, false positives. Char can be misidentified as tire wear or rotted biologicals rather than charred biologicals, false negatives."
"The definitions of “Soot” and “Char” are no more well defined than “Ash” which results in the inclusion of many more possible interferences. Many sources produce charred plant biomass that are not wildfire related. Charred wood from fireplaces is much more easily identified than charred bark or fine ash from leaves or other plant parts. Field burning, slash burning, and other non-wildfire combustion sources produce much more of the type of material identified by this approach. The burning of candles is identified in these reports as a possible interference for soot identified as being from wildfire. Basically, the reports indicate that the source of the particulate matter should not be assumed based on this analysis and that they are not responsible for how this information is interpreted. Further, the results are unreliable in that any change in the method could produce very different results of at least equal validity. That leads to the common and appropriate precaution added to most of these reports shown below. It should also be added that there are no “published standard methods” for wildfire analysis although their disclaimer suggests that some exist and they comply. That is a misstatement.
A Common Precaution Attached to “SC&A analysis” Results
The results are obtained using the methods and sampling procedures as described in the report or as stated in the published standard methods, and are only guaranteed to the accuracy and precision consistent with the used methods and sampling procedures. Any change in methods and sampling procedure may generate substantially different results. The laboratory assumes no responsibly or liability for the manner in which the results are used or interpreted.
Wildfire Smoke Exposure: A Comparative Study
The limitations of this approach are not necessarily due to the lack of skill on the part of the analyst but are limitations imposed by the way the analyst is required to perform the analysis."
"“Assemblage Analysis” Quantification is based on the area of a tapelift that must be examined in order to see the required wildfire assemblage. It has the advantage of being independent of the particles that are not related to wildfire."
"Laboratories using “SC&A analysis” use one of three referenced methods. The most common method is “Visual Estimate”. Visual estimate involves looking as the sample and estimating the relative amount of area covered by SC&A compared to the area covered by other types of particles. This is a notoriously inaccurate method when percentages are under ten percent, even when the material being quantified is well defined and being done by “experts”19,20. Differences of at least a factor of two are not uncommon between experts at a level of ten percent and the difference increases as the percentage decreases. Size also affects estimation. The reader is encouraged to look at Photograph 1 and 2. The amount of black material in those images was measured using an image analysis program. Does the amount of black materials in Photograph 2 look like five times as much as the black material in Photograph 1? The human eye is not good at estimating percent coverage in a field of view.
A second method of quantification used by some laboratories using “SC&A analysis” is to count particles and generate a percentage based on count. Although it might sound more scientific than a visual estimate in reality it is not. If all of the particles were the same shape and the same size it would be fine, but they are not. The analysis may be improved a little by only counting particles larger than a certain size, say three micrometers or larger. If the particles were all spheres that would help but do we mean three micrometers in length, in width, in equivalent spherical diameter, an average of six ferrets, or some other measure? Is there an upper limit restriction? Is one three micrometer particle the equivalent of a thirty micrometer particle? Visually estimated area coverage is beginning to sound better.
A third approach attempting to compensate for the defects in the second method is to use a random point array as the basis for counting. That sounds better but it also suffers from problems related to sample size, especially for materials at low percentage coverage or for particles of small size widely distributed"
"Assemblage analysis is the only approach that actually identifies the emissions from a specific wildfire as being present in an indoor environment."
"This study demonstrated that false positives and false negatives can dominate the results of a SC&A analysis. The chart on page 20 shows that values of 5% SC&A are possible when the presence of the wildfire assemblage is absent. It also shows that values of 5% or less SC&A are possible when the wildfire assemblage is present at high levels."
"The use of clear tape where the plastic is not removed doesn’t have sufficient optical quality for this type of analysis. The sample typically used for SC&A analysis is of inferior quality. That significantly limits the confidence in the identification of specific particles."
I understand there may be some inner-industry some controversy:
over the tape lift vs wipe vs micro-vacuum sample collection methods, as well as controversy
over light microscopy alone over light microscopy with advanced microscopy (SEM, TEM, EDX).
For me there is no controversy. The professional assessor should choose the tool they think is best suited to the conditions presented to answer the question they are tasked to answer based on their knowledge, education, and training. I don’t think the IICRC, AIHA, or any body should provide a hard rule (the dreaded “shall”) on collection and analytical tools.
As we discussed, in many cases investigators may be able to answer the question being posed without any sampling or lab analysis at all. (e.g. See a duck, hear a duck, smell a duck, then it is not a fish.).
The question of impacted or not impacted is not a health assessment. It is usually an assessment to determine if cleaning for the given event is warranted or not warranted. We avoid unnecessarily making assessments of this nature science fair projects.
Light microscopy is one of several methods we recommend. Keep in mind the lessons CSC and I learned using light microscopy alone for soot analysis only. This technique yielded “none detect” in around half of the initial samples from structures obviously visually impacted by three-dimensional fire debris in the 2002 Rodeo-Chediski fire samples. The lesson learned was light microscopy for soot alone is not the best choice to determine the presence or absence of fire debris indoors.
We still use light microscopy.
We ask the analyst to look for:
char (burned plant material with cellular characteristics),
soot (high carbon microscopic particles e.g. tiny charcoal), and
ash (salts remaining after burning soot and char completely).
In addition, we have samples analyzed by TEM, SEM, and EDX.
We reserve the option to use tape lifts, but we prefer composite wipes and/or composite micro-vacuum sample collection methods for combustion byproducts. All methods should be available since all methods have pros and cons.
Tape lifts are a viable option.
Advantages are:
Tape lifts are inexpensive to analyze
Tape lifts can better preserve the particle dispersion and morphology of collected particles over wipes and vacuum samples.
Tape lifts are thin, small, and inexpensive to ship or store
Disadvantages are:
You cannot run TEM, SEM or EDX on a tape lift
A tape lift is a very small sample area, so to represent a larger space, you may need to take many.
Tape lifts are more prone to sampler bias.
Tape lifts are not efficient for collecting dust on irregular, rough, or porous surfaces.
The resolution of optical microscopes has limitations.
Tape lifts are able to capture the dust at the surface only, so if time has elapse between fire and sampling, you may miss the lower layer of fire debris by collecting the post-fire settled dust.
Tape lifts are visual estimations and interpretations, so they rely heavily on the expertise of the microscopist. Microscopist experience varies wildly.
In some cases, like an Urban Fire, the assessor may be asked additional questions regarding compounds like lead, asbestos, arsenic, cobalt, or nickel. Direct microscopy is not appropriate in this case.
Wipe and vacuum samples are viable options
Advantages are:
You can represent multiple areas within a structure to determine the average impact.
You can represent multiple locations or an entire system/zone in a single composite sample (cost reductions)
You can collect wipes off smooth and hard surfaces and rough hard surfaces.
You can collect vacuum samples of porous surfaces.
Disadvantages are:
Some morphological characteristics and all dispersion characteristics are not preserved.
Composites do not tell you which of the multiple areas have deposition. Could be all, could be one, could be 3 of 4. You just know an average.
Advanced microscopy is more expensive per sample than direct microscopy alone.
