Strategies for Number of Samples
Surfacing Materials
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 taken for surfacing materials. The procedure for determining the number of samples to be taken for surfacing materials is as follows:
- Identify homogenous areas of suspect surfacing ACBM.
- Quantify the area (square footage) of each homogenous area of suspect surfacing material.
Apply the 3, 5, 7 Rule which indicates the minimum number of samples as follows:
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<1000 square feet 3 Samples
>1000 square feet, but <5000 square feet 5 Samples
>5000 square feet
For example, homogenous 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 take 9 samples for every homogenous area of 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 homogenous material. These are given unique sample numbers so 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 take 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 homogenous area of surfacing material.
