Decoding Asbestos Dust Sampling: What You Need to Know

Curious about the advantages and limitations of various asbestos detection methods? During my April webinar, I took a deep dive into settled dust sampling—a topic that's both technically important and practically relevant for industry professionals. Let's start with the basics: settled dust refers to those loose fibers and particles that collect on surfaces throughout buildings. For those who appreciate the technical details, ASTM defines it specifically as particulate matter measuring less than one millimeter in size. 

There are five collection methods at your disposal: the scrape and scoop technique, adhesive tape sampling, micro vacuuming, wet or dry wiping, and passive monitoring. Each of these settled dust methods has its inherent strengths and weaknesses. 

Missed the webinar? 

Watch: Asbestos in Settled Dust 

Spot Check of Visible Dust 

Imagine the following situation: you're conducting an inspection and notice visible dust that you suspect might contain asbestos. How do you confirm your suspicions? You begin by selecting a method for collecting a dust sample.  
 
The “scrape and scoop” offers an extremely simple approach. You use something rigid like a business card, scoop the dust up, place the collected material in a Ziploc bag, seal it, label it, fill out the chain of custody and send it to the lab for analysis. This technique is useful for quickly assessing relative levels of contamination and detecting the presence of asbestos in the dust and debris collected.  The samples may be examined by Polarized Light Microscopy (PLM) or Transmission Electron Microscopy (TEM) for the identification of asbestos. However, this method is not designed for precise quantification of asbestos fibers and is not suitable for regulatory compliance or legal purposes. 
 

Tape lift sampling involves applying standard non-frosted adhesive tape to the surface in question, then securing it to either a clean glass slide or directly to the interior of a Ziploc bag. This sampling technique is useful when evaluating potential contamination on various surfaces throughout a building, including floors, walls, and furniture. Compared to wipe sampling, sticky tape sampling has the advantage of preserving the fibers' original position and morphology when they are removed from the surface. Performing analysis using a technique such as Scanning Electron Microscopy (SEM) can provide semi-quantitative results and reveal the morphology and elemental composition of asbestos fibers. This allows for reliable identification of asbestos as well as associated non-asbestos materials, even in very fine or fragmented samples. 

Passive Dust Fall in Building Inspections 

When evaluating potential hazards in buildings, passive dust fall assessment offers valuable insights. During an inspection of a 12-story high-rise in New Jersey, I observed a typical scenario involving sprayed-on fireproofing (SOF) insulation on the structural steel beams and corrugated steel decking above suspended ceiling tiles. The SOF material can delaminate and settle on horizontal surfaces below when compromised through vibration, wire installation, or water damage from roof leaks. 

For situations where material appears to be delaminating and settling, we can perform a passive dust fall test to figure out if this is actively occurring or if we're looking at historic accumulation on horizontal surfaces.  

In contrast to the two methods discussed earlier, this approach suggests sampling times anywhere from one week to one year, with one month being the ideal duration. The method recommends using either a glass or plastic petri dish, or aluminum tins. Simply place these collection devices in your desired locations, document their placement with date and time, and establish your collection timeline. 

After retrieving the samples, you have multiple analysis options. While PLM (Polarized Light Microscopy) is technically possible, it's rarely effective as settled asbestos fibers are typically too small for light microscopy detection. For this reason, we strongly recommend TEM (Transmission Electron Microscopy) analysis, which provides comprehensive qualitative and quantitative results measured in fibers per gram or fibers per square meter per 30 days. This approach aligns with established ASTM methods specifically designed for dust fall collection and measurement. 

Hidden Asbestos: What You Need to Know About Testing 

Consider this scenario: settled dust in your building has become a silent reservoir for asbestos contamination that accumulates over the years. Asbestos containing building materials (ACBMs) can be found in a variety of building materials and objects, even seemingly innocuous ones. Common materials include old floor and ceiling tiles, mastic, joint compound, thermal insulation, roofing and siding materials, and pipe insulation. Additionally, asbestos can be present in less obvious places like window caulking, adhesives behind wallpaper, and even some decorative plaster. When renovation or demolition disturbs ACBMs, asbestos fibers can suddenly become airborne.

Here's the interesting part—even in environments with significant dust, if you hire a consultant who brings in air sample pumps a day or two after disturbance, you'll likely get an "all clear" result. That doesn't mean the environment is safe because air testing is most useful when assessing the air quality immediately after a disturbance, not a few days later. 

For a truly accurate assessment, we recommend two much better testing approaches: Micro Vacuuming and Wipe Sampling. These approaches provide a much clearer picture of what's really present in your environment. 

Micro-vacuuming is a sampling technique used to collect dust from surfaces for asbestos analysis. The process typically involves using a small vacuum nozzle with a specialized filter to capture those tiny particles. This technique is particularly valuable for those tricky porous surfaces like carpets, textured wood, or difficult-to-clean concrete floors where the settled dust is loose. Environmental professionals rely on this method to determine not just if asbestos is present, but exactly how much there is. For the technically minded readers, we follow the ASTM D5755 standard for this process and analyze samples using TEM. 

Wipe sampling, on the other hand, is simple yet effective. A technician uses a particle-free wipe to collect dust from a specific area, then sends that wipe to the lab for analysis . This works particularly well on smooth surfaces like tiles, painted walls, or glass where settled dust is bound to the surface. The best part? Wipe sampling has shown to have a better collection efficiency, especially in environments with sticky residues such as oil and grease. Professionals follow the established ASTM D 6480-05 method for reliable results. 

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In conclusion, it's important to recognize that each settled dust collection method has its own unique advantages and limitations. When dealing with loose dust, microvac sampling tends to be your best option. For dust that's adhered to surfaces, wipe sampling will generally yield more accurate results. And in situations where dust is actively accumulating, passive sampling methods should be your go-to choice. Just remember that air sampling only captures a moment in time and may potentially give you a false negative - something worth considering when planning your asbestos assessment strategy. Feel free to reach out if you have any questions about which method might work best for your specific situation! 

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