Assure 360

New analyst guidance part 2: testing for asbestos

Written by Nick Garland on 01/08/2017

In the second part of my summary of the Asbestos Analyst’s Guide from the HSE – I’m concentrating on asbestos testing (both bulks and air).

This is a stand-alone article, but you may also want to read the first instalment published earlier this year – New analyst guidance: appointing the right asbestos analyst.

This is a review of the ‘draft for consultation’ – there may well be changes before final publication. We still don’t have a release date for the final publication of the guidance, and we are already at the end of the promised June. However, the consultation was a surprise when it was issued over Christmas, so stand by your beds.

Whilst I am writing this for the layman – this instalment reviews some dramatic changes that all professionals will need to prepare for. It comes with my usual health warning – this is obviously a summary and clearly not intended to replace the Guide. The appendices contain a lot of important detail and should still be studied to gain the fullest picture.

Is it asbestos – and what is the risk?

Bulk sampling

The first section I will deal with in this instalment is analysis in bulk materials – or ‘bulks’ for short.

Simply put, this is where a small amount of a suspect material is collected on site and taken to a laboratory. Powerful microscopes are used along with special techniques to investigate the sample. This is the only sure fire way of determining whether a material contains asbestos and ultimately what risk it presents.

Bulk Sampling and asbestos surveys are required under the duty to manage (CAR 2012, Regulation 4) and under the current Construction Design and Management (CDM) Regulations.

Whilst HSG264 – Asbestos: the survey guide remains the best practice manual, the new analyst guide overlaps and takes things further in some areas. Both will need to be understood to remain compliant.

An end to solo working?

The guidance on single surveyor working has been significantly altered. It is now ‘strongly recommended’. The guide goes further by stating that some situations make it essential:

  • Working at height.
  • Confined spaces.
  • The method demands it – e.g. shadow vacuuming has been specified. This last might be needed where you can’t wet the asbestos containing materials (ACM) – e.g. live electrics.

We should take note – as this is much more forceful phrasing than the ‘ideally’ in the Survey Guide. The need to work from height in most or all surveys would seem to preclude solo working completely. Clearly, if single ‘man’ teams are now officially frowned upon, it will have an impact on prices.

What not to sample

The guide gives specific direction on sampling strategy for some ACM types. Mostly the advice is consistent with HSG264, but again with some exceptions. The first significant change is in the recommended strategy for pipe insulation.

HSG264 tells us:

“In general, one sample should be taken per 3m run of pipe with particular attention paid to different layers and functional items (valves etc). ”

Whereas the Analyst Guide says:

“Valves or hatches or repaired areas near access routes are less likely to contain asbestos but discretionary sampling may be necessary.”

Clearly a totally different approach, which I am not convinced about. Only the other week I attended a site where all the asbestos had been removed, except near the valves.

Another key change in guidance is in dust sampling, which should be avoided except in ‘rare and specific occasions’. Dust sampling should not form a routine method or approach when surveying. Low numbers of asbestos fibres in dust are to be expected in buildings which contain or have contained ACMs. Due to the sensitivity of the method, very low levels of fibres can be detected. However, the guide tells us the random presence of low numbers of asbestos fibres in dust is not significant and represents “inconsequential risk”. It also tells us – in the absence of any ‘visible’ suspicious asbestos debris and fragments, extensive cleaning or abatement works will not be necessary

This is very welcome guidance indeed. Asbestos occurs naturally in the air of all our industrial cities. The sensitivity of the bulk analysis process is likely to find even the smallest trace. Because such testing merely determines presence and not risk, it is too blunt a tool. Random swab samples, where there is no visible evidence of contamination have caused no end of issues to clients. A report containing such information can cause considerable alarm and remediation costs, where the reality might be a single isolated fibre posing little or no risk. See the section towards the end of this article on SEM and ‘Real Risk Assessments’.

What to sample and how

In traditional surveys, the number of samples taken will depend on:

  • The extent and range of materials present
  • The extent of variation within the materials
  • Building or site circumstances

The guide states that the number of samples should not be restricted by cost or contractual arrangements as this could lead to poor choices and false assumptions. This is much stronger guidance than previously published. I must stress that I fully support the increased emphasis, but it should be recognised that it will have an impact on costs.

Help can be obtained from original architect drawings, but will depend a lot on experience. The guide suggests ‘tells’ that will give a clue to a change in material:

  • Colour changes
  • Surface texture change
  • Sound (when knocked)
  • Evidence of repair
  • Temperature

None of the above can be used for positive identification, but they can give a strong indication as to when to take additional samples.

Consideration should be made where access makes sampling or post sampling clean-up impractical or hazardous. These areas should be discussed with the client. This is a continuation of the plan, plan, plan mantra of the survey guide.

On the sealing of the sampling point, the guide raises some important considerations. Specifically, it recommends that the chosen technique should be agreed with the client. Some issues to bear in mind:

  • Tape or the traditional encapsulant paint (ET150) may peel from loose, hot or damp surfaces
  • Water-based fillers may shrink and fall out as they dry
  • Foam sealants are often flammable

Safety alert!

On this last issue, there was a serious safety alert on the asbestos forum where some foam sealant used in an enclosure spontaneously ignited via static electricity.

Sampling Guidance

Spray coatings The guide suggests pre-injected with surfactant around the sampling area. It cautions against sampling damaged areas that show evidence of previous repair – whilst easier and safer, it may not be representative.

Pipe/thermal Full depth samples using a core sampler, but placing a wipe inside the tube before sampling and withdrawing the sampler through another wet wipe. This creates a plug at either end.

Insulating board/tiles The guide warns of proximity to live electrics, where pre-spraying might be hazardous. It also warns that a large sample is needed if the water absorption test is planned to determine AIB or cement (see below).

Asbestos cement Large samples are recommended (at least 5cm2) or where the water absorption test is required (9cm2). Asbestos cement is defined by CAR 2012 as a material, which is predominantly a mixture of cement and chrysotile and which when in a dry state, absorbs less than 30% water by weight. This leads to the Water Absorption test which is detailed in Appendix 3 of the draft guide.

Textured coatings Again large samples are recommended as asbestos is typically non-uniform (at least 20cm2). Areas of thicker material and/or ridges should be targeted. Two samples per surface or one per 25m2.*

Dust samples Avoid, but where they are taken to assess spread of a specific incident a minimum of one tablespoon of dust (not debris) should be collected. Scraping the dust layer into a pile and transferring into a suitable labelled container. Wipes, adhesive tape and filters should not be used.

* I have served my time in the bulk lab and can testify to how irritating small samples of textured coating are. However, I am not sure how a client would take to two 20cm2 sample from every ceiling. Certainly, something to discuss in the pre-survey planning.

Measurement of airborne fibre concentration

In layman’s terms, air testing. For asbestos, it is the collection of a measured volume of air (litres) through a filter. A specific area is examined (number of ‘graticules’ – see below), and the number fibres counted. This allows the calculation of the concentration of respirable (again see below) fibres in the air.

As the guide was intended for the use of clients as well as analysts and the above is likely to mean nothing to most readers – I will start by explaining a few terms:


In this case means not only breathable, but small enough that they can reach the lowest levels of the lungs where they can do the most harm.


Results are quoted in one of two ways – the first is by far the more dominant. f/ml or f/cm3 – i.e. number of respirable fibres counted for every millilitre or cubic centimetre of air drawn through the pump. 1ml is the same volume of air as 1 cm3.

Limit of Quantification (LoQ)

This is an oft used phrase that is little understood outside the analytical world. Results are often stated as less than the LoQ (e.g. <0.01f/ml). LoQ is a statistical way of determining what would be “fair to say”. E.g. if a given room had 100 fibres floating about and you sampled a small amount of the air – it would be pot luck whether you captured any of the fibres, but it wouldn’t be ‘fair’ to say that the air was asbestos free – just you didn’t detect anything. Similarly, if there were 1 million fibres floating about – you would be near certain of catching some. Therefore, LoQ is a statement that:

we don’t really know exactly how much asbestos is in the air, but it is less than ‘this’

Any clearer?


This is the round ‘target’ that the analyst can see when analysing the filter through the microscope. The target is moved randomly a set number of times and the number of fibres falling within that target are counted. The graticule is a specific area, and so if we know how many targets have been inspected, we know the precise area of the filter that has been analysed. Clearance tests would include 200 of these random movements, personals can have less. Therefore, if only 100 graticules are used this means ½ the time to analyse the sample but double the LoQ.

The guide details the two main types of air testing – personal and static.

Personal sampling

Where we test the fibre levels near to an individual’s face. The asbestos approved code of practice tells us what we should use this type of test for.

  • Establish that the Control Limit (0.1f/ml) is not liable to be exceeded
  • Aid correct selection of Respiratory Protective Equipment (RPE)
  • Help decisions on licensable work (the sporadic and low intensity measure)
  • The short-term exposure limit (STEL) has not been exceeded (the 10 minute STEL is 0.6f/ml)
  • Provide medical surveillance records
  • Support current and future risk assessments
  • Check the effectiveness of control measure

Whilst measurement against the control limit requires a 4-hour sample, there is allowance for shorter activities. It must be noted that when the time to access the enclosure and decontaminate following completion of a morning’s shift is factored in, a 4-hour task is a rare beast indeed.

In my opinion, all the above are important, but the last three have the most practical use. The removal contractor should be aiming for higher standards than the control limit to help drive performance. But only a test with a low LoQ can have any real utility. Therefore, the 10-minute test should be avoided in favour of one that can give a LoQ of 0.05f/ml or better.

My Assure360 database is designed specifically to deal with these three critical areas.

Clearly high risk activities should be prioritised – this may be related to the ACM, its condition or the individual’s role in the method. So, if a single test is to be completed it should be the operative scraping the pipe, not the one doing general spraying duties.

The analyst must record detailed observations about the operative during the testing:

  • Person’s name and job title
  • Actual work activities carried out (periods and extent)
  • General work activity in the area
  • Asbestos product being removed (e.g. AIB ceiling tiles)
  • Type(s) of asbestos likely to be involved
  • Removal method
  • Type(s) of dust suppression control measures employed
  • Type of RPE
  • An opinion on the effectiveness of control measures
  • Other factors which may affect the result (e.g. confined location, external location, condition of the material being removed or worked on, whether ACM nailed or screwed on)
  • Photo of work area (through viewing panel)

The guide specifically states that if any of this information is missing, the sampling will be deemed inadequate. Now this is a very strong statement indeed. I think it is intended to compel analytical companies to comply, rather than suggest to a contractor to ignore them.

Just like any asbestos worker, the analyst themselves should have personal monitoring conducted on them particularly:

  • Visual inspection and air clearance monitoring during 4-stage procedures
  • When collecting bulk samples.
  • When entering “live” enclosures for any reason e.g. for ‘pre-visuals’

A ‘summary’ of personal sampling should be kept for 5 years. There is no guidance on what this summary should contain. But the data should form part of the health records, which must be kept for 40 years.

My Assure360 database tracks the exposure, compares it against the anticipated level and allows the employer to review methods on a regular basis to improve standards. Whenever the anticipated levels are exceeded, this is treated just like any safety incident spawning an investigation and root cause analysis. These new-look certificates would come into their own at this stage – perfect evidence for the investigation. Upload them as a permanent link to the record. With nearly 4000 personals on the system now – it gives users a great deal confidence when setting and reviewing levels.

Static Sampling

This is the large traditional air test, where we establish the fibre levels in a general area. Used in several different situations:

  • Clearance testing- validation for the Certificate for Reoccupation process
  • Background testing – establishing the baseline levels or ‘starting point’. before removal / disturbance starts.
  • Leak testing – monitor the integrity of the asbestos enclosure during asbestos removal.
  • Reassurance testing – used after asbestos works have been completed – to give reassurance that the area remains safe.
  • Near-source static sampling – used during removal / disturbance to assess the general release / spread of asbestos caused by that activity. Can be used to simulate maintenance activity in a controlled manner or in very large enclosure.
  • Far-source / perimeter sampling – conducted around the perimeter of the site, e.g. around a contaminated land project, or around a building on fire.

There is no specified flow rate for static tests, but total volume of air tested should 480litres or more. The number of graticules (targets) counted must be 200+. However, the recommendation is that high flow rates (e.g. 16L / min for 30 minutes be used to limit the effect of settling and increase accuracy. The exceptions to this are background and perimeter monitoring – where low flow rates and very long durations are preferred.

When not to test

The guide gives some pointers on when not to test.

  1. During the 4-stage clearance for external works e.g. soffit removal. This is an area that often confuses removal companies and analysts. External asbestos removal (i.e. no roof to the enclosure) still requires a 4-stage clearance, but does not require an air test (the third stage of the process);
  2. Where the work is a single event of such short duration/low emission that suitable monitoring results could not be obtained in the sampling time. My reading of this is that the 10-minute test is ONLY suitable for establishing sporadic and low intensity;
  3. Personal sampling where ‘there are good reasons for expecting that the exposures will be very low and well below the Control Limit’;
  4. Where adequate information is already available to enable the appropriate RPE to be provided.

I have my doubts over the wisdom of the last two. We are mandated to reduce exposure so far as reasonably practical, therefore not testing because we don’t think exposure will be too high – or we already use good RPE – seems to miss the point. You should always conduct the test to ‘support current and future risk assessments’ and ‘check the effectiveness of control measure’.

Air monitoring by Phase Contrast Microscopy (PCM)

This is the name of the standard technique used to calculate airborne fibre concentrations. Paragraphs 5.10 & 5.11 give a great deal of detail on this, which I do not intend to reproduce here.

The technique has its advantages and disadvantages. Probably the key plus is that the test is quick (within an hour or two when conducted on site) and by comparison to the alternatives – inexpensive. Disadvantages are that high dust environments (e.g. wire-brushing, ‘blasting’ or removal of ceilings) can overload the filter making it unreadable (occluded). As it can’t easily differentiate between asbestos and non-asbestos fibres, it can overstate asbestos concentration.

These must be recognised and factored in when designing the sampling strategy. Careful selection of sampling periods/volumes or sequential samples (i.e. multiple tests run after each other, adding the results) should be considered. Another important strategy (where results may be skewed by non-asbestos fibres) would be the retention of half the filter prior to standard analysis. In the case of a ‘high’ result from the first half, the duplicate can be sent for a much more accurate Scanning Electron Microscopy (SEM) test – see below.

Caution should also be observed when interpreting the results from post incident air tests. The time gap between the incident and the test will be affected by natural dilution.

Scanning Electron Microscopy (SEM)

Whilst the guide details the option of using SEM analysis. It does not suggest it as a first option, but only as a check if PCM fails. However, in the case of blasting, where occluded filters are near certain, or very low LoQs are desirable, SEM testing should be considered. SEM can obtain LoQs as low as 0.0005f/ml and are much less vulnerable to overloaded filters.

One interesting service that is beginning to be available is ‘Real Risk Assessment’. The phrase was coined by Charles Pickles of Lucion referring to long duration air tests in normal (occupied) areas. Analysis by SEM would give very low limits of detection. Results could then be directly comparable to the World Health Organisation lifetime risk levels. This would finally measure chronic low level exposure and allow a genuine understanding of the long-term risks. Such accurate results could validate existing management techniques and prove that occupants are not being exposed, or, used to improve the plan.

In the case of 4-Stage Clearances (4SC), the guide indicates that the original floor surface should not be covered at the time of the air test. It does say that there are exceptions, but the only examples given is scaffolding or when the floor is an ‘intrinsically dusty surface’. This could be interpreted as meaning – floors sheeted out before removal must be uncovered for the 4SC air test. Hopefully clarification will be in the final version as many simple projects may become more complex and costly if this is the case.

Daily leak testing

The guide states that daily leak testing is required where there are other personnel near the asbestos work. Key areas to be tested are:

  • Enclosure openings (e.g. airlock, bag lock, additional flapped vents).
  • Areas where there had been difficulty sealing the enclosure (e.g. pipe or cable penetrations).
  • Areas occupied during the work.
  • Near the exhausts of NPUs if not venting to atmosphere.

Testing should be a combination of short and long duration – short just after removal commences, with longer duration following on after.

This is very clear direction that was lacking in the original 2006 analyst guide. Currently leak testing (certainly daily ones) is considered an optional extra. The new emphasis is unarguably a good idea – but the cost impact on projects will be significant.

Other than the PCM and SEM, two other sampling techniques are discussed in the guide:

  • Size selective samplers – these exclude larger particles allowing the analyst to focus only on respirable particles. Whilst this has some very useful applications (e.g. contaminated land projects) they shouldn’t be used in enclosures as high dust levels indicate inadequate cleaning.
  • Real-time samplers – as the name suggests these give a continuous reading of the particles in the air. Long considered the holy grail – these are still viewed with suspicion in the guide with only a single paragraph discussing them. The essence of the guide’s view is that they shouldn’t be used in place of standard techniques. However, I am aware that several trials are being conducted, under the watchful eye of the HSE – so opinion may change in the final version.

In my next feature I’ll be looking at how we can start preparing for new legislation.

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