Asbestos-Containing Materials and Testing Methods

“Does this building have asbestos?” is really two questions: which materials are likely to contain it, and how a laboratory determines whether they do. This article covers both.

Where asbestos-containing materials turn up

Asbestos was added to a wide range of building products, and the list is longer than most people expect. Materials that commonly warrant a closer look in older properties include vinyl floor tiles and the mastic beneath them; sheet flooring and its backing; acoustic ceiling texture and some wall texture coatings; joint compound; pipe and boiler insulation; cement siding, roofing felts and shingles; certain plasters; duct wrap and HVAC gaskets; and fireproofing sprayed onto structural steel.

Building age is a useful screening signal but not a rule. Products already in the supply chain continued to be installed after manufacturing declined, so a later construction date does not automatically clear a material. The EPA maintains a general overview of where asbestos may be found.

Friable versus non-friable

A material is described as friable when it can be crumbled by hand pressure when dry — insulation and some textures, for example. Friable materials release fibres more readily and are treated more cautiously. Non-friable materials such as intact floor tile or cement products hold fibres in a binder, but grinding, cutting or smashing them changes that quickly. The condition of the material and the work planned around it matter as much as what it is.

How bulk samples are analysed

Bulk material samples are normally analysed by polarised light microscopy (PLM), which identifies asbestos fibre types and estimates the percentage present. Where a result is near a decision threshold or the matrix is difficult — some floor tiles and joint compounds fall into this category — a laboratory may use point counting or transmission electron microscopy for a more sensitive determination.

PCM and TEM for air samples

Air samples answer a different question: how many fibres are airborne in the sampled area. Phase contrast microscopy (PCM) counts fibres above a certain size but cannot distinguish asbestos from other fibres, which makes it fast and well suited to worker exposure monitoring during abatement.

Transmission electron microscopy (TEM) resolves much smaller fibres and can identify them specifically as asbestos by their structure and composition. It costs more and takes longer, and it is the method typically specified for clearance decisions after abatement, where the question is whether the area has been cleaned adequately.

Choosing the right approach

The method follows the question. Planning a remodel in a 1970s house means bulk sampling of the materials in the work area. Monitoring conditions while abatement is under way means air sampling. Confirming cleanup at the end usually means TEM clearance sampling. A good scope is defined before anyone opens a wall, and it is written down.

If you are not sure which applies to your project, describe the building and the planned work when you call and we will explain the options.