Your occupational hygienist has sampled the air in your workplace, collected respirable dust on cassettes, and sent them to a laboratory for analysis. The results show that exposure is below the Workplace Exposure Standard (WES) of 0.05 mg/m³. But here’s the critical question: if a regulator questions those results, will a court accept them as evidence that your workplace is safe?
The answer depends on whether the laboratory analysing your samples is NATA-accredited. NATA accreditation is a small acronym with enormous implications for the legal defensibility of your silica monitoring results and, by extension, your WHS compliance.
This article explains what NATA accreditation is, why it matters for silica dust monitoring, what analytical methods accredited labs use, and how to verify that your testing laboratory meets the highest standards.
What is NATA?
NATA stands for the National Association of Testing Authorities. It is Australia’s independent, non-government accreditation authority for laboratories, inspection bodies, and reference material producers. NATA is internationally recognised and operates under the terms of a Mutual Recognition Agreement with accreditation bodies in other countries (ILAC — International Laboratory Accreditation Cooperation).
NATA’s role is to:
– Independently assess laboratories against international standards
– Issue accreditation certificates confirming technical competency
– Conduct surveillance audits to ensure ongoing compliance
– Maintain a public register of accredited bodies (searchable at nata.com.au)
NATA accreditation is voluntary — a laboratory can operate without it. However, many regulatory agencies and industry standards expect or require NATA accreditation for results to carry full legal weight. For occupational hygiene testing, NATA accreditation is increasingly seen as a baseline requirement for compliance with the Work Health and Safety Act.
What Does NATA Accreditation Mean for a Silica Testing Laboratory?
When a laboratory is NATA-accredited for silica dust testing, it means:
-
The laboratory has been independently assessed against ISO/IEC 17025 (the international standard for testing and calibration laboratory competence) and found to meet all technical, procedural, and quality management requirements
-
The specific analytical methods used by the laboratory for RCS analysis have been validated and accredited. The lab cannot simply claim to “measure silica”—NATA accredits the lab for specific methods (e.g., “FTIR analysis of respirable dust on MCE filters” or “XRD analysis of gravimetric dust samples”)
-
The laboratory participates in proficiency testing programmes. This means the lab regularly receives “blind” samples with known RCS content and must demonstrate that their analytical results match (within acceptable uncertainty) the true values. If results are consistently off, the lab loses accreditation
-
Quality management systems are in place. Records are audited, equipment is calibrated regularly, chains of custody are documented, and procedures are standardised
-
Measurement uncertainty is quantified and reported. NATA-accredited labs report not just a single number (“0.08 mg/m³”) but a measurement uncertainty range (“0.08 ± 0.015 mg/m³”), reflecting the precision and reliability of the result
Why NATA Accreditation Matters for Your Monitoring Results
Legal Defensibility
Imagine a regulator inspects your workplace, finds dust, and argues that your monitoring results are unreliable. If your testing was done by a non-accredited laboratory, the regulator can challenge:
– Whether the lab has validated its methods
– Whether the lab participates in quality assurance programmes
– Whether the analyst is competent
– Whether the measurement is accurate
If your testing was done by a NATA-accredited laboratory, the regulator’s challenge is much harder: NATA’s independent certification attests that the lab meets international standards. A court is far more likely to accept NATA-accredited results as reliable evidence of your compliance.
Accuracy and Reduced Risk of False Results
NATA-accredited labs participate in mandatory proficiency testing. Two labs analysing the same respirable dust sample should produce similar results; if one lab consistently overestimates or underestimates RCS, proficiency testing will reveal this, triggering investigation and corrective action. This system dramatically reduces the risk that your monitoring results are falsely reassuring.
Non-accredited labs have no such external quality assurance. A poorly trained analyst using unvalidated methods could report that exposure is 0.04 mg/m³ (below the WES) when the true value is 0.06 mg/m³ (above the WES). Without proficiency testing, this false result would go undetected.
Chain of Custody and Sample Integrity
NATA-accredited labs maintain rigorous procedures for sample receipt, storage, and analysis:
– Samples are logged with unique identifiers
– Storage conditions (temperature, light, humidity) are documented and controlled
– Analysis dates are recorded
– Results are checked by a second analyst before reporting
Non-accredited labs may have looser procedures, increasing the risk that samples are mislabelled, contaminated, or analysed long after collection (degrading the sample).
Method Validation and Silica-Specific Expertise
NATA accreditation specifically validates the analytical method, not just the laboratory’s general competence. A laboratory accredited for “FTIR analysis of respirable dust” has demonstrated that it can reliably distinguish respirable quartz from other dust components. A laboratory accredited for “XRD analysis on bulk samples” has different capabilities and is accredited for a different purpose.
This matters because analytical methods have limitations:
– FTIR (Fourier Transform Infrared Spectroscopy) is the most common method for analysing respirable dust on filters; it detects crystalline structures by their infrared absorption signature
– XRD (X-ray Diffraction) is more specific to crystalline phases and is often used for bulk or settled dust samples
– Both methods have minimum quantifiable concentrations below which they cannot reliably detect RCS
A NATA-accredited lab is transparent about these limitations and reports when results are at or below the minimum quantifiable concentration (MQC).
What Analytical Methods Do NATA Labs Use for RCS?
FTIR (Fourier Transform Infrared Spectroscopy)
FTIR is the most widely used method for analysing respirable dust samples in Australia. A worker wears a personal air sampler throughout the shift; respirable dust is collected on a filter cassette. The cassette is sent to the laboratory, where the filter is analysed by FTIR.
How it works: The FTIR spectrometer passes infrared light through the dust-loaded filter. Different minerals (quartz, feldspar, mica, etc.) absorb infrared radiation at characteristic wavelengths. The software compares the absorption spectrum to reference spectra and calculates the mass of quartz on the filter.
Strength: FTIR is quick, non-destructive, and suitable for low-concentration dust samples (down to ~0.01 mg/m³)
Limitation: FTIR cannot distinguish between different polymorphs of silica (quartz, cristobalite, tridymite) as reliably as XRD. Some confounding minerals can interfere with the quartz peak.
NATA accreditation for FTIR means the laboratory has validated the method, demonstrated accuracy in proficiency testing, and uses a NATA-approved reference standard.
XRD (X-Ray Diffraction)
XRD is used for bulk dust samples (settled dust from work areas) or for samples where FTIR is inconclusive. XRD measures the crystal structure of minerals; quartz has a distinctive diffraction pattern that XRD can identify with high specificity.
Strength: XRD is highly specific for crystalline phases and can distinguish between quartz polymorphs
Limitation: XRD requires larger sample masses and is less suitable for very low-concentration personal air samples
NATA accreditation for XRD is becoming more common as laboratories recognise the value of XRD for confirming FTIR results or analysing bulk samples from high-risk workplaces.
Gravimetric Analysis
Gravimetric analysis measures the total mass of respirable dust collected on a filter (by weighing the filter before and after sampling). This gives the total respirable dust concentration, not specifically the crystalline silica fraction. Gravimetric analysis is often performed alongside FTIR to provide context: e.g., “Total respirable dust: 2.5 mg/m³; RCS: 0.04 mg/m³.”
NATA accreditation for gravimetric analysis verifies that the laboratory’s weighing procedures, environmental controls, and balances meet ISO standards.
The Measurement Uncertainty Challenge at the WES Limit
Here’s a subtle but important issue: the WES for RCS is 0.05 mg/m³, and FTIR analysis—the most common method—has a minimum quantifiable concentration (MQC) of approximately 0.01–0.02 mg/m³ depending on the dust characteristics and sampler type. This means that personal air samples with RCS concentrations near 0.05 mg/m³ have measurement uncertainty that spans the WES threshold.
For example, a sample might be reported as “0.05 ± 0.015 mg/m³”—the true value could be anywhere from 0.035 to 0.065 mg/m³. If a single sample shows 0.05 mg/m³, you cannot definitively say whether exposure is above or below the WES; it depends on the measurement uncertainty.
AIOH and NATA position: When results are near the WES threshold, multiple samples are needed to establish a reliable exposure profile. A single sample at 0.05 mg/m³ is inconclusive; three samples averaging 0.04 mg/m³ with a range of 0.03–0.05 mg/m³ provides much better evidence of compliance. A NATA-accredited hygienist and laboratory will discuss this uncertainty with you and recommend appropriate sampling frequency and interpretation.
How to Verify NATA Accreditation
Before submitting samples to a laboratory, verify NATA accreditation directly:
- Visit the NATA register: Go to nata.com.au/search and search for the laboratory by name or location
- Check the scope of accreditation: The register shows which tests the lab is accredited for. Look for “Respirable Crystalline Silica,” “FTIR analysis,” “dust analysis,” or similar keywords
- Verify the accreditation is current: The register shows the accreditation date and expiry date
- Request the laboratory’s scope document: The lab should provide a detailed scope showing which methods, materials, and concentration ranges are accredited
Red flag: If a laboratory claims to analyse silica dust but is not listed on the NATA register as accredited for RCS testing, use a different lab.
Does NATA Accreditation of the Lab Mean the Hygienist Is Also Accredited?
No. Laboratory NATA accreditation and occupational hygienist certification are separate credentials:
- NATA accreditation certifies that the laboratory’s analytical methods and quality systems meet international standards
- AIOH certification certifies that the occupational hygienist (the person designing the monitoring program, collecting samples, and interpreting results) has the knowledge and experience to assess workplace RCS exposure
A NATA-accredited laboratory may employ a newly graduated analyst with minimal experience. Conversely, a highly experienced hygienist may work with a non-accredited laboratory (though this is increasingly indefensible for compliance purposes).
Best practice: Engage an AIOH-certified occupational hygienist to design your monitoring program and interpret results, and ensure samples are analysed by a NATA-accredited laboratory. This combination provides both expertise in exposure assessment and analytical reliability.
Frequently Asked Questions
Q: Is NATA accreditation mandatory for occupational hygiene testing?
A: No, it is not legally mandatory. However, under the Work Health and Safety Act and the Safe Work Australia Model Code of Practice, employers must ensure monitoring results are reliable. NATA accreditation is the most widely accepted evidence of reliability. As of December 2026, with the transition to the Workplace Exposure Limit (WEL) framework, NATA accreditation may become effectively mandatory for regulatory compliance.
Q: Can we use a non-accredited laboratory to save cost?
A: You can, but you are assuming all the risk. If a regulator questions your results, a non-accredited lab’s testing is harder to defend. If a worker later develops silicosis and claims exposure was under-reported, non-accredited testing is weak evidence in your favour. The cost saving (typically $50–100 per sample) is far outweighed by the compliance and liability risk.
Q: How often should we retest if results are below the WES?
A: This depends on the stability of your exposure sources and controls. If air monitoring shows consistently low exposure (<0.03 mg/m³) and controls are well-maintained, annual or biennial testing may be sufficient. If exposure is in the 0.03–0.05 mg/m³ range or if controls are new/untested, quarterly or semi-annual testing is more prudent. Your AIOH-certified hygienist should determine the appropriate frequency.
Q: If FTIR shows 0.05 mg/m³ and measurement uncertainty is ±0.015, are we non-compliant?
A: Not necessarily. A single result at the WES threshold is inconclusive. You should conduct additional sampling (3–5 samples over a period of weeks or months) to establish a reliable exposure profile. If the average of multiple samples is <0.05 mg/m³, you have evidence of compliance despite individual samples touching the limit. If multiple samples consistently exceed 0.05 mg/m³, you are non-compliant and must implement controls. Your NATA-accredited lab and AIOH hygienist should advise on the appropriate interpretation.
Q: What if our laboratory is NATA-accredited but our hygienist is not AIOH-certified?
A: Your testing is analytically reliable, but your sampling design and interpretation may not be. An uncertified person may design a monitoring program that misses high-exposure areas or fails to account for exposure variability. Best practice is to use both an AIOH-certified hygienist (for program design and interpretation) and a NATA-accredited laboratory (for analytical reliability).
Q: How long should we keep the laboratory reports and raw data?
A: All RCS monitoring records must be retained for at least 30 years under the Safe Work Australia Model Code of Practice. This includes original laboratory reports, sample cassettes (if stored), and any raw spectroscopy data. Silicosis has a latency period of 10–40 years; historical monitoring data may be critical evidence if a worker later develops respiratory disease.
Key Takeaway
NATA-accredited silica dust testing is not just a “nice to have”—it is increasingly a legal requirement for workplace compliance. Laboratory accreditation provides independent verification that your results are accurate, reliable, and defensible in the event of regulatory scrutiny. Combined with an AIOH-certified occupational hygienist to design your monitoring program, NATA-accredited testing gives you the highest confidence that your workplace is truly compliant and your workforce is protected.
Ready to Ensure Your Testing is Compliant?
Anitech Group partners exclusively with NATA-accredited laboratories for all silica dust analysis. Our AIOH-certified hygienists design monitoring programs tailored to your industry, collect samples using validated methods, and interpret results in the context of measurement uncertainty. Results you can rely on—in any compliance context.
[Request a Testing Partnership Discussion]
IMAGE_REQUIREMENTS
- FEATURE (1200x630px): NATA logo (if permitted) or stylised tick mark with “NATA Accredited” badge overlaid on a laboratory setup: FTIR spectrometer, dust cassettes, calibrated balance, quality control certificates visible. Title: “NATA-Accredited Silica Testing: Compliance You Can Defend.”
- BODY_1 (800x450px): FTIR spectrometer analysing a dust-loaded filter cassette, close-up of the infrared absorption curve on screen. Caption: “After What Analytical Methods Do NATA Labs Use?”
