Five Overlooked Asbestos-Containing Materials

Hazardous Materials Assessments

Industrial hygienists are often asked to assist property owners and facility managers to find asbestos at their sites. While the task is simple, its definitely not easy. Numerous challenges present themselves – materials in enclosed or hidden locations such as fixed wall cavities, ad hoc renovations conducted over the years which disrupt construction patterns, multiple layers of materials at a given location and partial or incomplete removal of building materials over time.

While these factors are outside of the hygienists’ control, a competent hazardous materials professional still needs to find and sample as many suspect materials as possible, contingent on the constraints imposed by the end-client or the site. So which materials are frequently missed?

1. Mastic Under Spray-Applied Insulation or Fireproofing

Many times, a material may be easily visible, such as a ceiling deck covered in spray-applied material (insulation or fireproofing), or a material may be commonly found in easily-accessible and identifiable locations, such as mastic on floor tiles, but an uncommon application of a material can catch hazardous materials professionals off-guard.

One such application is the use of mastic on ceiling decks, particularly on concrete decks, to assist with adhesion of spray-applied materials. Mastic may be applied to the ceiling deck surface in irregular patches, and in skim-like depths at each location. This makes it difficult to find when covered with the fireproofing material. Oftentimes, it may only be discovered if a patch of the spray-applied material delaminates and falls from the ceiling, exposing the underlying deck (ex: in the event of water intrusion), or during an active asbestos removal project.

What implication does this have? Several scenarios may apply, but of interest to the industrial hygienist are when either material is asbestos-containing, or when both are asbestos-containing. If the mastic was performing as intended, it will have adhered to the spray-applied material and intermixed to some degree at the surface of the mastic. While the spray-applied material can be removed, it is incredibly difficult to remove the mastic completely, and oftentimes a skim will remain on the surface of the ceiling deck. Chemically-based products may only smear the mastic on the surface. If a hazardous materials professional is asked to provide a statement at the completion of abatement activities which definitively states that all asbestos-containing materials have been removed, they will be in a precarious situation if mastic remains.

Similarly, if the mastic is not identified until abatement or removal activities are underway, the owner may be hit with significant additional costs from the asbestos removal contractor due to the labour-intensive methods typically needed to remove mastic.

2. Joint Sealants on Foam Glass or Cellular Glass Insulation

Industrial plant facilities typically do not have a wide variety of materials, but are more likely to have a large quantity or volume of the materials which are present. Depending on the nature of the activities conducted at the facility, heat is typically needed in the process, which in turn necessitates insulating materials on pipework.

A variety of insulating materials have been used of the years, including asbestos-containing cementitious materials, calcium silicates, fibreglass, refractory ceramic fibre (RCF) and more recently, foam glass or cellular glass insulation. While fibreglass and RCF insulations have their own inherent hazards, only the cementitious materials are typically asbestos-containing. These different types of insulating materials are also distinguishable based solely on their appearance. This visual identification can be misleading – a hazardous materials professional may correctly identify insulating materials as foam glass / cellular glass, but then incorrectly state that asbestos is not suspected to be present.  The catch is that asbestos-containing mastics may be present at the seams between sections of foam glass. Gaps typically exist due to the way in which the insulation is manufactured and installed. See below for a diagram of a typical construction format – mastics are usually applied at the location marked as ‘joint sealant’.The factors which complicate the assessment include the fact that the foam glass insulation and mastic / joint sealants are usually both black. If a site owner restricts the extent of damage that can be incurred to the pipe cladding, it is difficult for the hazardous materials assessor to hit the right spot to expose a joint in the foam glass insulation. So while the mastic or joint sealant makes up a relatively small portion of the insulation on pipework, it is not feasible or cost effective to try to remove the mastic from the foam glass insulation. The result is that asbestos-containing mastic on foam glass essentially necessitates consideration of and removal of all of the insulating materials as asbestos-containing materials, albeit they can typically be removed in a low-risk format due to the non-friable nature of the mastic. The assessor runs the risk of concluding that asbestos-containing materials are not present on the pipework if the mastic is overlooked.

3. Residential Siding Materials

It’s frequently common to find that when an assessor arrives at a property to conduct an asbestos assessment, the focus is on the interior of the building and the building finishes which are commonly observed during day-to-day occupation of the building.

A risk is that the assessor may neglect the exterior of a building altogether, or incorrectly exterior finishes as non-suspect.

When it comes to residential asbestos surveys, a product used on houses constructed between the 1950’s and 1970’s in North America which has the potential to be asbestos-containing is horizontal cladding. 

The suspect materials can be identified by their appearance – wider than vinyl siding, typically given a faux-wood grain appearance, approximately 1/4″ in thickness and often found to be a cement-like material. If these suspect sidings are present on the exterior of a residence, it’s also a good indication that there’s a greater potential for asbestos-containing materials elsewhere at the property.

4. Multiple Layers of Wall or Flooring Finishes

Many hazardous materials professionals can easily correctly identify certain wall and floor finishes as suspected to contain asbestos, such as plasters, vinyl sheet flooring, vinyl floor tiles, drywall joint compound and similar.

The risk in this regard is the potential for multiple layers of materials to be present at a given location. For example, old buildings which are frequently renovated, such as hotels, are notorious for new aesthetic finishes to be installed directly over existing finishes. This saves the property owner costs since materials are not first removed; however, the result is that asbestos-containing materials may be left in place, enclosed, and forgotten. Common examples are drywall or gyprock installed over plastic wall finishes, carpet installed over vinyl flooring, or any number of flooring finishes installed over levelling compounds or mastics.

The assessor must make efforts to check through as many layers of materials as reasonably practicable to reduce the potential for missing sub-finishes. Similarly, the assessor should also try to check for multiple layers of finishes in a variety of rooms in the building, to address the potential for renovations having been conducted in only a handful of locations.

5. Light Fixture Foil Paper

The last material on our list is not one that is usually present in extensive quantities in a building, but often has a very high asbestos percent content (>80%).  The material is a foil paper heat shield found in certain light fixtures. 

If the assessor is able to access the light fixtures and remove the glass or plastic diffusive covering, the foil paper is typically easily-accessible and easy to sample. Due to the high asbestos content, and the potential for live electrical lines in the fixture, appropriate precautions should be taken to sample the material in a safe manner. The foil paper is also reasonably easy to remove as part of an abatement; however, depending on the size of the building and the number of light fixtures present, the quantities may add up and result in significant cost implications.


Asbestos-containing materials seem to be so ubiquitous that it appears it may have simply been used as a filler substance in many products. So where have you found asbestos-containing materials? Have you been caught off-guard in high profile circumstances? Let us know in the comments below.

February 4, 2018

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