The Difference Between a Traceable and NATA Gas Detector Calibration
The Importance of Gas Detector Calibrations
A gas detector calibration is the process of comparing the readings of a gas detector to a reference instrument to ensure they are consistent. The reference instrument serves as a reliable benchmark, and after exposing both instruments to the same concentration of gas, any deviations in the gas detector’s readings from the reference can be corrected. Regular calibrations are essential to ensure that the readings on your gas detectors are accurate and reliable throughout repeated use in the field. Calibration intervals can vary depending on factors such as the type of instrument, the gas being detected, environmental conditions, and manufacturer recommendations, meaning that the interval will not always be consistent. The level of accuracy in a calibration can also vary, with standards and accreditations that help businesses to gauge the level of precision a laboratory can provide them with.
What is a Traceable Gas Detector Calibration?
A traceable calibration, also known as a standard calibration, entails testing a detector against a calibrated reference instrument that can be traced back to a certified reference material (CRM). In Australia, the National Measurement Institute (NMI) is the laboratory that provides CRMs, and is a government agency that is responsible for maintaining the national standards of measurement in Australia. When a gas detector is calibrated, it is compared to a CRM that can be traced to the International System of Units (SI) for global accuracy. This ensures that the gas detector is accurate and that it is measuring the concentration of the gas correctly.
With a traceable calibration, the accuracy of the reference instrument is ensured through a clear connection to the NMI, with either the instrument itself or another instrument used in the chain of calibrations being a CRM. This is similar to comparing a centimetre on two different rulers. If there is no assurance that a centimetre on the reference ruler is accurate, the reference could be incorrect, and matching the second ruler’s measurements to this wouldn’t improve its accuracy. Hence, a gas detector used as a reference in a traceable calibration must be able to be traced back to the NMI.
By default, all gas detector calibrations should be traceable. This ensures that their readings are trustworthy and enables accurate and reliable monitoring of potentially hazardous gases, both for safety and compliance purposes.
What is a NATA Gas Detector Calibration?
A NATA calibration builds on a traceable calibration and is performed by a laboratory that has been accredited by the National Association of Testing Authorities (NATA). NATA is an independent, non-government organisation that provides accreditations to testing and calibration laboratories in Australia by auditing them against standards such as the ISO/IEC 17025.
ISO/IEC 17025 is an international standard recognised in Australia and outlines the general requirements for a laboratory to be considered competent in the provision of testing and calibration services. By defining a globally recognised level of competence, ISO/IEC 17025 helps to facilitate cooperation across countries, indicating that results produced are valid and trustworthy. NATA acts as a reliable, government recognised body that evaluates laboratories based on standards to provide meaningful accreditations. They also audit accredited laboratories regularly to ensure that their high level of competence is maintained in the provision of NATA calibrations.
As part of the requirements, a NATA calibration must also have traceability, but differs slightly from a traceable calibration. Instead of only requiring the reference instrument to be part of a chain of calibrations traceable to the NMI, a NATA calibration must be conducted directly with a CRM. Given that the calibration is performed directly as opposed to with another instrument that has been calibrated by the CRM, it is more accurate and provides less margin for error, making it suitable for applications where the detector requires precision, reliability and accuracy.
What are the Key Differences Between a Traceable Calibration and a NATA Calibration?
The main difference between a traceable gas detector calibration and a NATA gas detector calibration is the level of assurance that the calibration is accurate.
In general, a NATA calibration is considered to be more accurate than a traceable calibration. This is because NATA accredited laboratories are subject to rigorous audits to ensure that they meet the highest standards of quality and competence in accordance with ISO/IEC 17025. While both calibrations have traceability, a NATA calibration is also more thorough, and requires more steps to ensure that the gas detector can measure gas concentrations to a higher degree of accuracy. By comparison, traceable calibrations have less requirements, and therefore will not necessarily have the same level of precision.
It is important, however, to note that both traceable and NATA calibrations are considered to be accurate enough for most purposes. The choice of which type of calibration to use will depend on the specific requirements of the application and the level of assurance desired.
Feature
Traceable Calibration
NATA Calibration
Accuracy
Accurate
More accurate
Accreditation
Not required
Required by NATA
Audits
Not subject to audits
Subject to rigorous audits
Cost
Less expensive
More expensive
Suitable For
Most purposes
Applications where high accuracy is required
When is a NATA ISO/IEC 17025 Calibrated Gas Detector Required?
While calibrations from a NATA ISO/IEC 17025 accredited facility are not generally considered mandatory or enforced by regulation, some industries and standards consider it best practice. The AS/NZS 2290.3:2018 standard for coal mining, for instance, assists with compliance by outlining requirements for monitoring and inspection equipment used in coal mining, encouraging NATA ISO/IEC 17025 calibrations as best practice. Businesses may also require their instruments to be handled by an accredited laboratory to guarantee accuracy and maximise safety for their workers, especially in high risk environments. Other cases where a NATA calibration may be required includes when a body such as the Environmental Protection Authority (EPA) require NATA endorsed reports to prove compliance.
