Independent guidance · Survey guides
Bulk Sample Analysis
How UKAS 17025 laboratories analyse bulk samples using polarised light microscopy to identify the fibre type and confirm presence.
Key takeaways
- Standard PLM: £30–£60 per sample
- Same-day: £60–£120
- Express overnight: £45–£90
- Bulk (10+ samples): £20–£40 each
- TEM / SEM specialist: £150–£400 per sample
An independent consultancy view of UKAS bulk analysis — what to demand, what to ignore, and how the certificate should read. Bulk sample analysis is the laboratory side of asbestos identification — the work that happens after a competent surveyor has taken a sample and before the dutyholder makes a decision based on the result. The UK method is MDHS 77, prescribed by the HSE, and the qualifying lab accreditation is UKAS ISO/IEC 17025. Together these two things turn a piece of suspect material into decision-grade evidence that the HSE, insurers, lenders and competent surveyors will accept. Get either part wrong — non-UKAS lab, off-method analysis, careless reporting — and the certificate is not worth the paper it is printed on. This guide explains the method, the accreditation, the reporting and the limitations.
The MDHS 77 method in plain English
MDHS 77 ('Asbestos in bulk materials: sampling and identification by polarised light microscopy') is the HSE's prescribed UK method for identifying asbestos in bulk samples. The analyst receives the sealed double-bagged sample, opens it inside a Class I microbiological safety cabinet to control fibre release, sub-samples representatively under a stereo microscope, mounts suspect fibres on a glass slide in a calibrated dispersion liquid (Cargille refractive index liquids), and examines them on a polarised light microscope with crossed polars and a quartz wedge. Each of the six commercial asbestos minerals has diagnostic optical properties — refractive index, sign of elongation, pleochroism, extinction angle, dispersion staining colours — that allow positive identification at concentrations above approximately 0.001%.
What this means
MDHS 77 is the only method whose result HSE, UKAS-accredited labs and competent surveyors all accept. Reports following any other method are outside the UK regulatory framework.
The six fibre types and how they are distinguished
Chrysotile (white asbestos, serpentine): curly fibres, refractive index ~1.55, weak pleochroism, parallel extinction. Amosite (brown asbestos, amphibole): straight brittle fibres, refractive index ~1.66, parallel extinction. Crocidolite (blue asbestos, amphibole): straight fibres, blue pleochroism, refractive index ~1.70. Anthophyllite, tremolite and actinolite (less common, amphibole group): each has its own diagnostic optical fingerprint. PLM also distinguishes between asbestos fibres and similar-looking non-asbestos fibres including man-made mineral fibres (MMMF), cellulose, gypsum needles and Wollastonite — a step that requires real analyst experience and that is the most common source of analyst error in non-accredited labs.
What this means
Six asbestos minerals, each with a distinct optical fingerprint. Distinguishing them from non-asbestos look-alikes is the part that needs accredited competence.
What UKAS 17025 actually audits
UKAS audits ISO/IEC 17025 accredited labs annually against: staff competence (each analyst individually assessed and re-assessed); equipment calibration (microscopes, refractive index liquids, balances); method validation (every variation of MDHS 77 the lab runs is formally validated); sample handling (chain of custody from receipt to disposal); proficiency testing (the lab participates in external schemes such as AIMS and gets scored against blind samples); reporting (every certificate format is approved); and audit trail (every result is traceable to the analyst, the equipment, the calibration and the proficiency test history). A lab that is not on the UKAS schedule for asbestos identification by PLM has none of these assurances.
What this means
UKAS audits people, equipment, method and audit trail — not just the result. That is what makes the certificate defensible.
Why PLM does not quantify percentage
MDHS 77 is a presence/absence method — it identifies fibre types and reports whether they are present in the sample. It does not quantify the percentage of asbestos in the material. Quantification by PLM is unreliable below ~10% content and is not part of the method. Some labs offer a separate quantitative analysis by ashed weight, area projection or gravimetric methods, but these are out of scope of the standard UK certificate. Reports claiming a percentage figure — '15% chrysotile' — are either using a non-standard quantification method (which should be flagged on the certificate) or are not following MDHS 77 at all.
What this means
MDHS 77 says yes or no. It does not say how much. Be wary of certificates that quote percentages without flagging the quantification method.
Cost and turnaround
Standard PLM analysis: £30–£60 per sample. Same-day analysis (sample at the lab by mid-morning, result by close of business): £60–£120 per sample. Express overnight: £45–£90. Bulk analysis (10+ samples in one consignment): £20–£40 per sample. Specialist methods (TEM for soil samples, SEM for very low concentrations): £150–£400 per sample. Postage from competent persons to the lab is standard practice; the lab provides appropriate transport packaging on request. Most labs accept samples between 09:00 and 16:00 for same-day processing.
- •Standard PLM: £30–£60 per sample
- •Same-day: £60–£120
- •Express overnight: £45–£90
- •Bulk (10+ samples): £20–£40 each
- •TEM / SEM specialist: £150–£400 per sample
What this means
Standard PLM is fast and cheap. The cost is dominated by who takes the sample, not by what the lab charges to analyse it.
How the certificate is structured
A compliant UKAS 17025 PLM certificate contains: lab name and address; UKAS accreditation number and scope; certificate number and date; sampler details (name and qualification); chain-of-custody references; sample number, location and description as provided; date of receipt and date of analysis; method (MDHS 77); analyst name; result for each fibre type assessed (e.g. 'Chrysotile detected', 'Amosite detected', 'No asbestos detected'); any caveats on sample condition; and an authorising signatory. The wording 'No asbestos detected' is precise — it means no asbestos was identified at the limit of detection of the method, not that the material is asbestos-free as a whole.
What this means
Read the wording exactly. 'No asbestos detected' is sample-specific. The whole-material question still depends on heterogeneity and sampling density.
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Heterogeneity and multiple-sample strategy
Materials applied in layers, batches or assemblies vary point to point. A textured coating may have asbestos in the base coat and not in overlays. A vinyl floor may have asbestos in the tile and not in the adhesive (or vice versa). A mixed-age cement roof may have asbestos in some panels and not in others. A single sample of a heterogeneous material can return 'no asbestos detected' even where the material as a whole contains it. The proportionate strategy for any significant decision is multiple samples at multiple points and at multiple depths — typically two to three for a single room ceiling, more for a whole roof or a multi-room area.
What this means
One sample is one data point. Two or three at different locations and depths is the baseline for any decision that matters.
Specialist methods — TEM, SEM and quantification
Where PLM is insufficient — very low fibre concentrations, soils, made-ground, ultra-fine fibres below PLM resolution — transmission electron microscopy (TEM) or scanning electron microscopy (SEM) is used. TEM is the gold standard for fibre identification and is mandatory for some specialist applications (drinking water analysis, ambient air around former industrial sites, post-incident contamination assessment). It is significantly more expensive (£150–£400 per sample) and slower (3–10 working days), and not all UKAS-accredited bulk-sample labs hold TEM accreditation — check the scope on the UKAS schedule before commissioning.
What this means
PLM is the workhorse. TEM and SEM are the specialist tools — needed for soils, very low concentrations and specialist applications, and at a different price point.
Proficiency testing — the external check on the lab
UKAS-accredited bulk-sample labs are required to participate in external proficiency testing schemes — most commonly AIMS (Asbestos in Materials Scheme), run by Health and Safety Laboratory. Blind samples are sent to the lab, the lab returns results, and HSL scores the lab against the known answer. Performance is monitored and persistent failures trigger UKAS intervention. Proficiency testing scores are not normally published per-lab but are available on request and form part of the UKAS audit. A lab unwilling to share its current AIMS performance should not be used for any significant work.
What this means
Ask the lab for its current AIMS performance score. A confident accredited lab will share it; a reluctant one is telling you something.
Limitations of the method
PLM cannot identify fibres below the resolution of the optical microscope (~0.2 µm). It cannot quantify concentration. It cannot distinguish chrysotile from some non-asbestos serpentine minerals without dispersion staining (which is why the method requires it). It cannot reliably identify asbestos in heavily painted, heavily coated or thermally damaged samples without sample preparation that may itself release fibre. It cannot be applied to soil or air samples — those require different methods (TEM for soil, PCM/SEM/TEM for air). Within these limits, MDHS 77 is the prescribed UK method and the certificate is the prescribed UK evidence.
What this means
Know the method's limits. Ultra-fine fibres, heavily damaged samples, soils and air all need different methods — PLM is not a universal solvent.
Frequently asked questions
What does 'no asbestos detected' mean?
No asbestos fibre was identified in the specific sample analysed, at the limit of detection of MDHS 77 (~0.001%). The result applies to that sample only, not necessarily to the whole material if it is heterogeneous.
Why doesn't the certificate state a percentage?
MDHS 77 is a presence/absence method — it identifies fibre types but does not quantify concentration. Quantification by PLM is unreliable below ~10% content and is not part of the standard method.
What does PLM analysis cost?
£30–£60 per sample for standard analysis, £60–£120 for same-day, £20–£40 for bulk (10+ samples). Specialist TEM/SEM methods are £150–£400 per sample.
How long does the analysis take?
Standard turnaround is 24–72 hours from receipt at the lab. Same-day analysis is available if the sample reaches the lab by mid-morning. TEM/SEM specialist methods take 3–10 working days.
What is UKAS 17025 and why does it matter?
ISO/IEC 17025 is the international laboratory standard, awarded in the UK by UKAS. It audits staff competence, equipment, method validation, sample handling, proficiency testing, reporting and audit trail. A non-UKAS certificate is not accepted by the HSE, insurers or competent surveyors.
Can I send a sample directly to the lab?
Most UKAS labs accept samples from competent persons only (BOHS P402 qualified). DIY submissions are usually declined because chain-of-custody and controlled-sampling requirements are not met.
What fibre types does PLM identify?
All six commercial asbestos minerals: chrysotile, amosite, crocidolite, anthophyllite, tremolite and actinolite. It also distinguishes asbestos from look-alike non-asbestos fibres including MMMF, cellulose, gypsum needles and Wollastonite.
Can the same lab quantify asbestos content?
Only by separate methods outside MDHS 77 (ashed weight, area projection, gravimetric). These should be flagged explicitly on the certificate. Most UK decisions are made on presence/absence without quantification.
What about samples from soils or made-ground?
Soils and made-ground require different methods — typically TEM under the CL:AIRE protocol — and a different lab accreditation scope. Standard PLM for bulk materials is not the right method for soils.
How do I check the lab is properly accredited?
The UKAS schedule is public and searchable at ukas.com. Look up the lab by name, check the scope includes asbestos identification in bulk materials by PLM to MDHS 77, and check the schedule is current.
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Read next
For this section- Asbestos SamplingHow competent sampling and chain-of-custody underpin the lab's ability to apply MDHS 77.
- Air MonitoringThe other UKAS-accredited measurement — air fibre counting rather than bulk identification.
- Management SurveysWhere the bulk sampling done during a survey fits in the wider compliance picture.
- Asbestos Removal Costs in the UK (2026)What the identified fibre type and material drives in terms of removal regime and 2026 UK price.