Why is it important to calibrate a climatic chamber?

Temperature testing is a crucial step for some products. A concrete example is the aviation industry, where every detail can make a difference, especially given the extreme weather conditions to which airplanes are subjected.

For this reason, it is extremely important to regularly calibrate a climatic chamber, in order to use it correctly and, above all, to obtain consistently reliable and precise results.

A change in temperature, even just one degree, can have a serious impact on industrial products, bio-based devices, automotive products, and electronics.

This guide was created to inform users of the numerous benefits of calibration. In the following paragraphs, we will see:

1. The advantages of calibrating a climatic chamber
2. The time interval between the various calibrations
3. How to choose a good calibration laboratory
4. The parameters that must be considered in the calibration

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What are the advantages of calibrating an environmental chamber?

The calibration of a climatic chamber changes over time, just like any other measuring device. The only way to maintain accuracy and enjoy optimal performance is to perform periodic calibrations.

Below are the benefits of accurate periodic calibration:

The precision

Frequent calibration helps maintain the accuracy of climate chambers and eliminate the risk and potential damage that could result from incorrect measurements.

The consistency

If climate chambers are not calibrated, they may provide inconsistent results from a test, making it difficult to reach a definitive conclusion.

Reliability

If the calibration of an instrument is not reliable, the results will not be as reliable.

Loyalty

A calibrated climate chamber ensures that the instrument complies with industry and administrative standards and can be used in complete safety.

Traceability

Every time a climatic chamber is calibrated, paper records are provided. This will help track the instrument's deviation and help establish a correct calibration interval.

The time interval between the various calibrations

As mentioned, the primary purpose of calibration is to ensure the accuracy and reliability of your equipment. Constant use of measuring instruments exposes them to wear and tear, which naturally impacts their performance.

To maintain the overall efficiency of a climate chamber, calibration should be performed as frequently as possible. The interval between calibrations will depend on the following factors:

The manufacturer's advice

Climatic chamber manufacturers typically provide information on when and how the instrument should be calibrated. This initial information certainly helps determine the correct interval.

Before or After a Major Project

It's vital to ensure a climate chamber is functioning optimally before embarking on a major project. Likewise, even when a climate chamber is used for major projects and for extended periods of time, it must be calibrated. This is because frequent use can significantly impact the accuracy and performance of the instrument itself.

Duration and Degree of Use

Ideally, duration and degree of use should be the factors that determine the need for recalibration. This means that each calibration should be tailored and the frequency should vary according to its use.

Equipment Injuries

Equipment damage is almost inevitable. The most common problem with climate chambers is internal overload, which is typically the result of heavy use. When overload occurs, it's important to recalibrate the climate chamber before using it again.

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All of the above criteria should be taken into consideration when developing a calibration program. In the long run, an occasional calibration will cost more than a regular calibration.

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How to choose a good calibration laboratory

Expertise and compliance with the highest standards should be your top priorities when looking for a laboratory to calibrate your instrument. The following guidelines will help you choose the most suitable provider.

An Accredited Laboratory VS a Non-Accredited Laboratory

Both accredited and non-accredited laboratories can provide calibration services. It is therefore important to understand what it means to be qualified. A reputable calibration laboratory is considered qualified if it follows criteria established by accredited bodies, which include the laboratory environment, personnel, and traceability. 

Choosing an accredited laboratory guarantees the accuracy of the calibration service you will receive.

The Benefits of Choosing an Accredited Laboratory

• Confidence in calibration results
• Technically competent staff
• Equipment Traceability
• Controlled Laboratory Environment
• No uncertainty in measurements.

Accredited calibration laboratories must follow the highest industry standards, namely ISO/IEC 17025 and clause 7.1.5 of ISO 9001:2015.

What should be included in the calibration service

When looking for a calibration provider, make sure they offer a comprehensive service. For quality calibration, it's important to include the following:

Accurate Measurement Tests

The goal of a calibration is to ensure its accuracy and therefore reliable results. When choosing a supplier to perform a calibration, you need to be sure they have the accurate instruments to perform the test.

Measurement of the Uncertainty Coefficient

The supplier you choose should be able to assess the uncertainty factor present in the measurements of the instrument being calibrated. Knowing the uncertainty factor is important for calculating the accuracy of measurements. This will also allow you to determine how the performance of the measuring instrument changes.

Measurements and Calibration Traceability

Traceability is the key to reliable calibration, but it's too often taken for granted. If measurements and calibrations are traceable, it's possible to trace them back to national standards and thus achieve higher quality.

Calibration Certificate

A quality calibration service provider will always provide you with a certificate of calibration. This document contains calibration data and will also serve as official proof that your device has been properly calibrated.

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Calibration of the FDM Climatic Chamber

We at FDM – Environment Makers deliver the climate chambers to our customers already perfectly calibrated.

Not only that. We can also perform calibrations on specific points requested in advance by the customer, such as temperature 30° and humidity 50%, if these are the values ​​the customer will be using most often.

For any further questions or requests, please do not hesitate to contact us.

Reference Standards

• ISO/IEC 17025:2017 — General requirements for the competence of testing and calibration laboratories. Fundamental requirement for accredited calibration laboratories.
• ISO 9001:2015 clause 7.1.5 — Monitoring and measuring resources, metrological traceability of test equipment.
• UNI EN 60068-3-5:2018 — Confirmation of the performance of temperature chambers, standard methodology for mapping and qualification of thermostatic chambers.
• UNI EN 60068-3-6:2018 — Confirmation of the performance of temperature/humidity chambers, extension for climatic chambers with humidity control.
• UNI CEI 70099:2008 (VIM) — International Vocabulary of Metrology, standardized terminology for calibration and comparisons.
• EURAMET cg-20 — Calibration Guide for Thermostatic and Climatic Chambers, European Reference Methodology.

Authoritative Sources

• ACCREDIA. Italy's sole accreditation body for LAT calibration and LAB testing laboratories according to ISO/IEC 17025.
• INRIM – National Institute for Metrological Research. Custodian of the Italian national standards for temperature and humidity.
• EURAMET, the European Association of National Metrology Institutes, publishes Calibration Guides.
• BIPM – International Bureau of Weights and Measures. International metrological authority, custodian of the International System of Units and ITS-90.

Frequently Asked Questions about Calibrating Environmental Chambers

How many measuring points are needed for a mapping according to IEC 60068-3-5?

IEC 60068-3-5 requires a minimum of 9 points for volumes up to 2 m³ and 15 points for larger volumes, arranged at the corners and at the center of the useful volume. The reference sensors must be positioned no closer than 100 mm from the internal walls and heating/cooling elements to avoid direct influences. Mapping is performed with the chamber empty and, where required, also at a simulated full load to evaluate the impact of the specimens on the thermal gradient. For each set point (typically -40 °C, +23 °C, +85 °C, +125 °C), data is recorded for at least 30 minutes in steady state, then spatial uniformity (difference between hot and cold spot) and temporal stability (standard deviation of measurements over time) are calculated. The results are reported in the calibration certificate with expanded uncertainty k = 2.

What is the difference between calibration and IQ/OQ/PQ qualification?

Calibration operation that establishes the relationship between values ​​indicated by chamber instruments (integrated probes) and reference values ​​traceable to the SI, returning deviations and uncertainties according to ISO/IEC 17025. The IQ/OQ/PQ qualification is a broader process required in the GxP (pharmaceutical, biotech) sector: IQ – Installation Qualification verifies correct installation and documentation; OQ – Operational Qualification evaluates operation within specifications through vacuum mappings at multiple set points; PQ – Performance Qualification validates performance with real load under conditions of use. Calibration is a technical prerequisite for the OQ, but the qualification adds audit trails, SOP procedures, approved protocols, and reports compliant with 21 CFR Part 11, FDA 211 CFR, and EU GMP Annex 15.

How often should a climate chamber be recalibrated?

Frequency depends on usage, criticality, and regulatory requirements. The industry standard requires annual calibration for chambers in heavy use or in GMP/aerospace environments. For R&D laboratories with moderate use, biennial calibration may be acceptable, provided that intermediate checks are performed (checks with a reference thermometer). Chambers used in ICH Q1A/B pharmaceutical stability studies require semi-annual or annual calibration depending on criticality. After significant maintenance (replacement of the compressor, probes, doors), transportation, or after exceeding the maximum acceptable drift (typically ±0.3°C on temperature), recalibration is mandatory before returning to service. The procedure also includes monthly intermediate checks with reference probes, compliant with ISO/IEC 17025 clause 7.7.

How is measurement uncertainty handled in the calibration certificate?

The expanded uncertainty U = k × u_c (typically k = 2, corresponding to a 95% confidence level) is calculated by combining the uncertainty contributions of the reference sensor (ACCREDIA certified), measurement repeatability, volume uniformity, and temporal stability. For a good-quality climatic chamber, the typical expanded uncertainty is U = ± 0.3 °C for temperature and U = ± 2% RH for relative humidity. The certificate reports for each set point: nominal value, mean measured value, deviation, expanded uncertainty, and coverage factor. For pharmaceutical GMP applications, MKT (Mean Kinetic Temperature) and recovery time after door opening are also evaluated. The decision rule specifies the compliance criteria considering measurement uncertainty, with guard bands to avoid false positives/negatives.