Why Is There Variation in Asbestos Results?

It has been found, from experience and testing, that:

• asbestos in building materials such as stipple and lath and plaster can vary from room to room in a property
• the results from different laboratories can vary
• soil samples from the same site can be both positive and negative, even if they are sampled from the same place

 

Will All Labs Give the Same Result?  

• Identical samples can return a mixture of positive and negative results from different labs
• Positive results indicate that asbestos has been detected – negative means it has not been detected or seen

 

How To Best Protect All from Exposure

• In the case of properties which have returned a mixture of positive and negative results, the best risk management strategy is to treat all results as positive
• Raise awareness of this vulnerability so that informed decisions can be made

 

What Does a Negative Result Mean?

A negative result means that no asbestos has been detected. It is not a 100% guarantee that it is not present. It is highly unlikely to be present. If a reputable ISO 17025 accredited laboratory has performed the analysis, it is expected that there will be a very low chance of asbestos presence.

 Why Can Asbestos in Some Samples Be Missed?

Analysis of stipple and lath and plaster samples for asbestos requires the analyst to detect asbestos fibres in these samples. These samples can be very difficult to analyse.  The challenges faced include:

• These fibres are very small and easily missed
• Fibres can be present in low concentrations
• The other components (such as plaster) can easily hide the asbestos fibres
  • this often requires chemical pre-treatment or
  • heat treatment to remove the other material
• High numbers of samples being analysed and often demand for quick turn around of results
• Variation within a sample – only a small part of the sample is analysed and the amount of asbestos can vary
• The sample that is gathered may not be representative of the surface being sampled; the asbestos may vary across a surface
• Other components in the sample may dilute the asbestos component. This is especially the case with lath and plaster if not sampled correctly

 

Variation in Building Material

The addition of asbestos to building materials was not always constant.

• It has been reported that plasterers would at times add it manually, possibly leading to variations of asbestos distribution
• It was not always used; some houses are positive in the new parts of the house and negative in the older parts of the house
• Some materials sourced may have asbestos and some may not
• Renovations can make the location of the asbestos variable

Sampling Method

At K2 Environmental, we:

• Train staff on where asbestos is found – having an accredited lab that performs analysis enables us to train the sample team to target materials and locations where asbestos is typically found
• Understand how to obtain a reliable sample
• Where possible, sample multiple locations of a surface
• Minimise the amount of non-asbestos material that can dilute the sample

Asbestos in Jointing Compound

Positive results for jointing compound have been found in some properties. It is not a widely accepted practice to sample this material; however, it is now standard practice at a number of companies to sample all jointing compound.