How Many Asbestos Bulk Samples are Needed?

Asbestos was used as insulation and to strengthen other building materials. Building materials, like popcorn ceiling texture, were usually mixed onsite and applied, typically at one time in one location, but not always.

So, the standard for asbestos bulk sampling of Presumed Asbestos Materials is a minimum of 3, 5 or 7 bulk samples per material. The number of samples needed is determined by the square footage of the same material.

Asbestos Popcorn Ceiling Texture

What are surfacing materials?  Surfacing materials are building materials that are sprayed, troweled-on, or otherwise applied to surfaces (such as acoustical plaster on ceilings, fireproofing, etc.) for acoustical, decorative, or fireproofing purposes. Surfacing materials are the biggest concern of the AHERA regulation because of their friability and/or presence in public areas. The EPA funded the production of a guidance document for sampling friable asbestos-containing materials that was published in 1985. This was years prior to the AHERA regulation. This document was entitled: “Asbestos in Buildings: Simplified Sampling Scheme for Friable Surfacing Materials”. This document is often referred to as the “Pink Book”. Many of the recommended practices in this document were adopted by the AHERA Final Rule as regulations. The main recommendation adopted by AHERA (and thus OSHA by reference) was the number of samples to be collected for surfacing materials.

  1. The procedure for determining the number of samples to be taken for surfacing materials is as follows:Identify homogeneous areas of suspect surfacing ACBM.
  2. Quantify the area (square footage) of each homogeneous area of suspect surfacing material.
  3. Apply the 3, 5, 7 Rule which indicates the minimum number of samples as follows:
    <1000 square feet   3 Samples >1000 square feet, but <5000 square feet   5 Samples >5000 square feet   7 Samples
    For example, a homogeneous area of suspect ceiling plaster measuring 3500 ft.² would need to have five samples collected. These minimum number of samples required by AHERA and recommended by the “Pink Book” were created to minimize errors due to lack of uniformity in the distribution of asbestos throughout the material and laboratory error.

The “Simplified Sampling Scheme for Friable Surfacing Materials” actually recommends that the inspector takes 9 samples for every homogeneous area of the suspect material. The AHERA regulation did not make this recommendation mandatory for schools, realizing the costs involved in taking that many samples. In addition to the required number of samples for surfacing materials based on their area, the “Pink Book” recommends taking quality control samples. These samples are to check the consistency of the results obtained from a laboratory. The inspector can obtain a quality control sample by taking two samples immediately adjacent to each other of the same homogeneous material. These are given unique sample identification numbers so that the laboratory analysts cannot readily identify the quality control sample. Any major discrepancy between the actual sample and the quality control sample will require additional quality assurance procedures – even more samples of the same material. The major discrepancy example would be a result of less than 1% on the actual sample and a result of 50% on the quality control sample. EPA’s “Pink Book” recommends that the inspector takes at least 1 quality control sample per building or one per 20 samples, whichever is larger. Because it is a laboratory check on the asbestos content of the material, it should be done per homogeneous area of surfacing material.

Thermal System Insulation

The AHERA/OSHA protocol for required number of samples for thermal system installation is as follows:

  1. Take a minimum of 3 samples from much of this area of thermal system installation.
  2. Take one sample for patched sections of thermal system installation if the patched section is less than 6 linear feet or 6 ft.².
    In order for the inspector to detect a patched section, there must be some difference in color or texture from the rest of the thermal system installation. It is not homogeneous with the rest of the material. Therefore, if the patched section is greater than 6 linear feet or 6 ft.², it is a separate homogeneous area of TSI and would require a minimum of 3 samples. This would be true even if the patched section was 8 ft.².
  3. Take samples “in a manner sufficient to determine” of mudded fittings “per mechanical system”.
    Asbestos-containing mudded fittings (elbows, tees, valves, etc.) were on-site mixtures. Asbestos was mixed with other substances in water to make a mud. This was applied around the fittings and allowed to set. Since the process of making the asbestos-containing mud was not rigidly controlled by a manufacturing process, the percentage of asbestos in mudded fittings can vary from even fitting to fitting on the same system. Mudded valves are also a high maintenance item. They are continually being fixed or replaced in older systems. These two facts necessitate that in order for the inspector to “sufficiently determine” if a homogeneous area of mudded joints are asbestos-containing or not, more than one fitting should be sampled.

The Industry Standard ( a common way of conducting sampling versus regulatory compliance) is to take 3 samples at a minimum of any homogeneous area of suspect ACBM. A minimum of three samples was required by the 1982 Friable Asbestos in Schools Rule, it is the minimum for surfacing and TSI, in general, and was espoused in EPA’s Asbestos Sampling Bulletin of September 1994 when discussing the sampling of taping mud on drywall systems.

A sampling of mudded fittings is required to be conducted per mechanical system. The inspector or inspection company must arrive at a consistent definition of a “mechanical system”. Some companies define the mechanical system as the entire HVAC system or plumbing system. Most companies will, at a minimum, divide the HVAC system into sub-systems. These are (1) Heat or cold source (Boiler/Chiller), (2) distribution lines, (3) heat/cold exchangers, and (4) return lines. Sampling will be done per sub-system for the mudded joints and the pipe insulation. The rationale for sampling in this method is that each sub-system would have different insulation needs. For example, in a steam heated system, the distribution lines would need a high insulation factor to ensure the steam reaches the heat exchangers before cooling and condensing. The return lines do not meet the same insulation factor so the inspector might expect a different type of pipe insulation or different percentages of asbestos in the materials. Other companies will further divide the system and conduct sampling per pipe function.

No samples need to be collected from any homogenous area of thermal system installation if the accredited inspector determines that the TSI is fiberglass, foam, rubber, or other or non-ACBM.

The inspector must determine that the insulation is non-ACBM. The burden of proof lies with the accredited inspector so he/she must be confident with his/her method of determination. Non-ACBM insulation on duct work and pipes has been found to have asbestos-containing paper underneath the non-ACBM insulation.

Some of the jackets or mud applied over non-ACBM insulation has been found to
contain asbestos. Therefore, when in doubt, sampled the material.

Miscellaneous Material
AHERA/OSHA required the miscellaneous suspect ACBM be sampled “in a manner sufficient to determine” per homogeneous area of material. Floor tiles should be sampled per tile color and size. Ceiling tiles should be sampled by color, dot pattern, and size. If the inspector goes by the industry-standard, he/she will take three samples of each
material.

Resilient Flooring Materials
The inspector should remember that nonfriables could be assumed to contain asbestos. If the inspector opts to sample the floor tile, mastic, or vinyl floor sheeting, he/she should be aware of the following in order to sample “in a manner sufficient to determine”:

If the floor tiles are in a symmetrical pattern, (e.g. checkerboard pattern) the inspector could assume that they were all laid in at the same time so the mastic underneath the tiles is homogeneous. It is always best to visually check this. If the floor tiles are in a non-symmetrical pattern, the inspector could surmise that these tiles are patches and laid down at different times. In this case, the inspector must assume that the mastic underneath these different colors was applied at different times so the mastic might not be homogeneous
material.


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