Asbestos heating pipe insulation in poor condition Photo Guide to Visual Asbestos Risk Assessment in buildings
     


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Visual guide to asbestos risk assessment in buildings: This article discusses basic asbestos risk factors in buildings, simple visual inspection procedures, and summarizes current best judgment on removing versus leaving asbestos alone indoors. Visual inspection for asbestos is not a substitute for forensic investigation, air and dust sampling to detect asbestos contamination in buildings due to disturbance of that material. This is part of our document which assists building buyers, owners or inspectors who need to identify asbestos materials (or probable-asbestos) in buildings by simple visual inspection.

Also see ASBESTOS DUCTS, HVAC a field identification guide to visual detection of asbestos in and on heating and cooling system ducts and flue vents.

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ASBESTOS RISK ASSESSMENT - Asbestos Risk Factors

Asbestos suspect sheet flooring from a historic home in Vermont

Asbestos, a mineral fiber mined from the earth and used as a fire proof insulating material as well as in other products, has been a major occupational and safety hazard of great concern since the 1930's.

Out of the work place, in homes and offices, there are also potential health hazards, in particular if asbestos material is damaged, disturbed, in poor condition, or located where it is likely to suffer these effects.

But often asbestos-containing material can and should simply be left alone, undisturbed. Unnecessary disturbance of asbestos materials in such buildings is at risk of creating a more severe hazard than leaving it alone. In other cases asbestos encapsulation may be recommended.

The decision to leave asbestos alone, encapsulate it, or removing asbestos depends largely on the type of material, its location, its condition, and its exposure to mechanical damage or fiber release. Comments at each example shown in this document indicate the reasons that further asbestos testing or removal are likely to be needed or likely to be unnecessary.

Human exposure to airborne asbestos fibers has been linked to asbestosis and is a health hazard. Here is a series of photographs of places I've found common asbestos materials in buildings, and also where I've found recognizable asbestos in a few surprise locations.

Tremolite asbestos microphotograph (C) D Friedman We also look at asbestos fibers in our forensic microscopy lab, but we're addressing on-site visual inspection for asbestos here, not polarized-light microscopy such as our lab photo of crocidolite.

Curved asbestos fibers chrysotile. Straight asbestos fibers are amphiboles. The five amphiboles include amosite, anthophyllite, tremolite, actinolite, crocidolite. Chrysotile is the most commonly-found asbestos fiber.

The carcinogenicity of asbestos varies according to fiber length and diameter. The most dangerous fibers were those longer than 8microns and less than 1.5 microns in diameter.

Asbestos fibers shorter than 3-5 microns in length were reported to have a very low, if any, carcinogenicity. (According to McCrone who in turn quoted studies by King, Klosterkotter, Hilscher, Davis Stanton, Pott, eta als.)

The Essential Asbestos Questions to Ask in Assessing the Asbestos Hazard Risk in a Building

Asbestos floor tile package dataWalter McCrone posed the following 5 key things that a building owner should know in deciding what to do about possible asbestos in his or her building:

  1. Are fibers present?

  2. Are they asbestos?

  3. If there are asbestos fibers present, in what proportion of the total?

  4. What other substances are present (cellulose fibers, mineral wool, fiberglass, vermiculite, talc, perlite, pumice, diatomaceous earth, organic fibers, clays, glass powder, quartz, calcite, gypsum (drywall dust), plaster dust, etc.) [some additions by DJF]

  5. What is Friability (how easily are particles released into the air), effectiveness of existing isolation or encapsulation. [McCrone refers to asbestos materials which are friable - and so are more likely to be present in air, dust, or the environment. The floor tiles described by the box at left do not release high levels of asbestos fibers unless they are subjected to abrasion.
    See ASBESTOS FLOOR TILE IDENTIFICATION for details. -- DF]

McCrone's five questions are focused on the examination of a particle sample, probably an air sample of an indoor environment being tested for asbestos. Field experience suggests adding a 6th and a 7th question:

  1. Is there obvious, visibly recognizable asbestos or asbestos-suspect material in the building? (Some building materials are unmistakably asbestos or asbestos-containing and can be identified without lab analysis. They are shown in photographs provided below.)
  2. Is the asbestos friable? Perhaps re-stating #5 above in a compound question on friability: what is the general condition of the asbestos material? Is it damaged and thus more likely to be friable? Is it in a location which is likely to move asbestos particles into an occupied space by air movement or by human movement?

In effect, these questions assist in evaluating the potential asbestos hazard in a building. Simply looking at a snapshot of airborne asbestos particles is very unreliable.

Our work examining airborne particles in a large number of buildings indicates that very significant variations in the level of airborne particles (of all kinds) occur as a result of variations in normal building activity such as whether or not people are even in the building, fans being turned on or off, windows open or shut, vacuuming of surfaces during "cleaning", etc.

So a "low" number in any airborne particle measurement is not, alone, reliable in characterizing building risk. [DF]

 

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Or see ASBESTOS in POOR CONDITION

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ASBESTOS RISK ASSESSMENT at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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