The AHERA/OSHA protocol for the required number of samples for thermal system installation is as follows:
Take a minimum of 3 samples from much of this area of thermal system installation.
Take one sample for patched sections of thermal system installation if the patched section is less than 6 linear feet or 6 ft².
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 ft², 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 ft².
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 the water to make 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 for the inspector to “sufficiently determine” if a homogeneous area of mudded joints is asbestos-containing or not, more than one sitting 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 a 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 heated steam 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 homogeneous area of thermal system installation if the accredited inspector determines that the TSI is fiberglass, foam, rubber, or other 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, sample the material.