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PROFECTRONICS
Technical article · Test technology

Leak rate measurement: methods, detection limits and conversion

A leak tightness requirement is a number with a method, a test pressure and a temperature condition. Without these data, a leak rate in the customer specification does not specify a requirement that a test can verify.

Context

Content and validity

Customer specifications frequently copy leak tightness requirements without test conditions. A typical entry is “leak rate less than 10⁻³”. The entry does not give test pressure, tracer gas, test time and temperature stability. These 4 data decide the test equipment: a pressure decay test bench or a helium leak detector. A helium leak detector costs approximately 10 times as much as a pressure decay test bench.

This article sorts the methods by their documented detection limit. It explains the conversion between gases and units. A calculation example shows the largest source of error in the most frequently used method: the temperature, not the leak.

01

Definition of the leak rate

The reference is a closed, evacuated vessel with a volume of 1 l. If the pressure in it increases by 1 mbar per second, the leak rate is 1 mbar·l/s[1]. The leak rate is a pV throughput and not a mass. Thus it depends on temperature and gas type. Both quantities must be part of the specification.

The usual standard conditions are 1 013.25 hPa inlet pressure against approximately 0 hPa outlet pressure at room temperature[2]. Vacuum technology usually calculates at 20 to 25 °C. The ASTM practices for mass spectrometers use standard cubic centimetres at 0 °C[3]. The difference between the 2 references is 7 to 9 %. For an acceptance limit, this difference is relevant.

For the order of magnitude: a circular hole with 0.1 mm diameter lets approximately 1 mbar·l/s through at 1 bar pressure difference[4].

Leak tightness criteria per application

The vacuum literature contains a table of criteria for classification that is decades old[1]. The table is not a standard. But it gives the correct orders of magnitude.

Leak tightness criteria per application
CriterionLeak rateRemark
watertight (droplet formation)< 10⁻² mbar·l/stypical requirement for a cooling circuit in the field
vapour-tight< 10⁻³ mbar·l/s“sweat” on the joint
bacteria-tight< 10⁻⁴ mbar·l/sparticle diameter approximately 1 µm
oil-tight< 10⁻⁵ mbar·l/sapplicable to oil and fuel circuits
gas-tight< 10⁻⁷ mbar·l/slimit for refrigerant and vacuum applications
technically “absolutely tight”< 10⁻¹⁰ mbar·l/sthe measured quantity is permeation, not a defect

On the last row: the lower end of detection is at approximately 10⁻¹² mbar·l/s. By calculation, this leak rate is equal to an opening of 1 ångström[1]. In this range, no method measures a material defect. The method then measures the passage of gas through the intact wall. Thus a leak tightness requirement in this order of magnitude is a material requirement and not a production requirement.

02

Standards for leak tests

Since 2017, the European family of leak test standards has 2 parts. One part changed into ISO standards. The other part still has the status of 1999 and 2001. Thus, before you refer to a standard, check the status of the standard.

Standards for leak tests, research status August 2026
StandardSubjectEditionStatus
EN 1779Selection of test methods and techniques1999-10valid, draft prEN 1779:2024 in preparation[5], [6]
EN 1593Bubble emission techniques1999-11valid, not replaced[7]
EN 13184Pressure change method2001-07valid, not replaced[8]
EN 13185Tracer gas method2001-07withdrawn[9]
EN ISO 20485Tracer gas method2018-05valid, replaces EN 13185[10], [11]
EN 1330-8Terminology of leak tests1998-07withdrawn[12]
ISO 20484Terminology of leak tests2017valid, successor of EN 1330-8[13]
ISO 20486Calibration of reference leaks for gases2017valid[14]
ISO 18081Leak detection with acoustic emission2024-07valid, replaces edition 2016[15]

Withdrawn standards in documents. “Leak rate to EN 1330-8” and “tracer gas method to EN 13185” refer to withdrawn documents[9], [12]. Current manufacturer documents still contain both references. The valid documents are ISO 20484 for the terms and ISO 20485 for the method.

Industry uses pressure change measurement more than any other method. With EN 13184 from 2001, this method has the oldest and least detailed standard basis of the full family.

In the USA, the practices for mass spectrometers are current. They give explicit sensitivity ranges:

  • ASTM E493/E493M, inside-out method: 10⁻¹⁰ to 10⁻⁶ Pa·m³/s for helium[3]
  • ASTM E498/E498M, tracer probe: from 1 · 10⁻⁸ Pa·m³/s[16]
  • ASTM E499/E499M, detector probe: from 1 · 10⁻⁷ Pa·m³/s[17]

The frequently quoted guide ASTM E479 for the preparation of a leak test specification is inactive[18].

03

Methods and detection limits

The overview combines values from 3 independent manufacturer compendia and one technical publication[1], [2], [4], [19]. Some values differ by one decade. This scatter is a result in itself. If a source gives a theoretical limit and a limit achieved in practice, the figure shows both values.

10⁻¹² 10⁻¹⁰ 10⁻⁸ 10⁻⁶ 10⁻⁴ 10⁻² 10⁰ LEAK RATE · mbar·l/s Ultrasonic / acoustic Bubble test in immersion bath Pressure decay with air Differential pressure Pressure rise in vacuum Helium sniffer test Forming gas 95/5 (H2) Helium accumulation Helium vacuum integral test WATERTIGHT BACTERIA-TIGHT OIL-TIGHT GAS-TIGHT ABSOLUTELY TIGHT PRESSURE-BASED TRACER-GAS-BASED ACHIEVED IN PRACTICE
Fig. 1 · Comparison of detection limits, logarithmic. The bar shows the range between the theoretical limit and the limit achieved in practice. The black dot shows the value that is robust in practice. Between pressure decay and helium integral test, there are approximately 8 decades. Values from Pfeiffer[2], Leybold[1], INFICON[4] and Block[19].

The figure shows 3 ranges in which the sources agree. These values are suitable for a customer specification:

  • Pressure decay with air: theoretically approximately 10⁻⁴ mbar·l/s, realistic in industry 10⁻³ to 10⁻² mbar·l/s[4].
  • Helium sniffer test: 10⁻⁷ to 10⁻⁶ mbar·l/s.
  • Helium integral test in the vacuum chamber: approximately 10⁻¹² mbar·l/s, the same in all 3 compendia[1], [2], [4].

Properties of the methods

Pressure decay. The method needs little effort, is fast and has a low cost. It reacts strongly to temperature changes, up to the point where it is not usable (see section 04). Other documented limits: water condensation causes incorrect measurements. In vacuum technology, the method has almost no importance[1].

Pressure rise in vacuum. The manufacturer states that the method prevents the temperature effects[4]. But outgassing of the wall has an effect. One criterion separates the 2 effects and must be part of each test specification. If the time for a specified pressure rise stays constant, there is a leak. If the time increases, the cause was outgassing[1].

Bubble test. The method is visual and standards cover it, but it has 2 disadvantages. The wet test part must dry after the test[4]. In cycle-based production, this costs time. With foam spray, the result depends on the attention of the inspector[4]. Thus foam spray is not a capable process.

Acoustic emission. ISO 18081 gives a fundamental physical limit: turbulent flow causes detectable emissions, laminar flow usually does not[15]. Gas leaks give stronger signals than liquid leaks. In two-phase flow, cavitation causes signal peaks. These peaks are at least one order of magnitude above the turbulence signals[15].

Forming gas instead of helium. A mixture of 95 % nitrogen and 5 % hydrogen detects leaks of 5 · 10⁻⁷ mbar·l/s. The tracer gas is the hydrogen in the mixture. Hydrogen has 3 advantages over helium[19]:

  • The atmospheric background of hydrogen is 0.5 ppm, of helium 5 ppm. This gives a 10 times better basis for the signal-to-noise ratio.
  • The dynamic viscosity of hydrogen is 8.7 µPa·s, of helium 19.4 µPa·s. Thus, in laminar flow, pure hydrogen flows through a leak more easily. This advantage applies only to pure hydrogen. Forming gas with 95 % nitrogen flows approximately like nitrogen.
  • The gas does not adhere to surfaces, and a purge removes it significantly faster. This decreases carry-over and purge times.

To ISO 10156, the mixture is not flammable. Its cost is a fraction of the cost of helium[19].

Dye penetrant test. Systematically, this method is not part of this overview. ISO 3452-1 describes a test method for surface cracks[20]. The method gives no quantitative leak rate. It finds the location of a leak, but it does not measure the leak rate.

04

Pressure decay method: effect of temperature

The basic equation: at a leak rate q, a pressure equivalent Δp escapes from a volume V in the time Δt[1].

Δp = q · Δt / V

The difficulty is elsewhere. A temperature change in the closed volume changes the pressure in the same way as a leak. The value is usually larger than the leak signal. A decrease in temperature simulates a leak. An increase in temperature simulates leak tightness.

The ideal gas law at constant volume gives directly:

Δp / p = ΔT / T

At room temperature, this is 0.34 % of the absolute pressure per kelvin. 2 independent sources confirm this value[21], [22]. At 1 bar absolute pressure, 1 K is approximately 3.4 mbar. At 2 bar absolute pressure, it is approximately 6.8 mbar.

A calculation example shows the effect in a real test. The values are: test volume 110 cm³, test pressure 2 000 mbar absolute, 23 °C, permitted leakage 0.5 cm³/min, test time 5 s[21].

0+0.5−0.5 −0.38 +0.68 +0.30 permitted leakage 0.5 cm³/min over 5 s temperature rise 0.1 K the measurement shows a pressure rise: the part looks tighter than tight PRESSURE CHANGE IN 5 s · mbar Test volume 110 cm³ · test pressure 2000 mbar abs. · 23 °C
Fig. 2 · Superposition of leakage and temperature drift in the pressure decay method. The leak at the permitted limit causes −0.38 mbar in 5 s. A temperature rise of 0.1 K causes +0.68 mbar. In total, the test bench measures a pressure rise: the part with the leak looks tighter than a tight part. Numerical values from Dr. Wiesner Steuerungstechnik[21].

A temperature rise of 0.1 K reverses the sign of the measurement signal. This gives 3 countermeasures: temperature stabilisation, differential pressure measurement against a reference part, or a different method.

Resolution of the pressure sensor

Also without temperature drift, the resolution of the pressure transducer limits the method. An application report gives an example. It is not possible to show a calculated pressure decay of 7.2 · 10⁻⁴ mbar on a scale of 5 bar. Instruments with this resolution are not available[23]. One source gives approximately 0.1 Pa, or 0.001 mbar, as the practical lower limit[24].

This gives the smallest detectable leak rate. The equation is a derivation by Profectronics and not a formula from a standard:

qmin = V · Δpresolution / Δt

The smallest detectable leak rate is proportional to the test volume and to the sensor resolution. It is inversely proportional to the test time. Thus the method fails for large volumes. For large test specimens, the flow method has an advantage. In this method, the restriction of the laminar flow element sets the test time, not the volume[22].

Influences without sources. The research found no quotable source with numbers for the adiabatic temperature rise during the fill and the stabilisation time after it. The effect is clear: the gas becomes warmer when it flows in, then cools to the wall temperature and causes an apparent pressure decay. Each test bench must find the applicable stabilisation times for its geometry. The same applies to the quantitative effect of humidity. For this, the sources give only qualitative statements[1], [23].

05

Conversion between units, gases and media

Units

Documented conversions
Quantityis equal to
1 Pa·m³/s10 mbar·l/s[1], [4]
1 atm·cm³/s1.013 mbar·l/s[4]
1 sccm0.0169 mbar·l/s (1.013/60)[4]

From gas to gas

The applicable law depends on the flow regime in the leak[1]. In laminar viscous flow, the leak rates are inversely proportional to the dynamic viscosity. In molecular flow, they are inversely proportional to the square root of the molar mass. The transition is in the range of approximately 10⁻⁶ to 10⁻⁴ mbar·l/s[1]. A second source states that the leak rates of helium and air start to differ at approximately 10⁻⁴ mbar·l/s. Below 10⁻⁷ mbar·l/s, molecular flow is dominant[2].

The source gives the factors for the most usual pair[2]:

laminar: qair = 1.08 · qhelium
molecular: qair = 0.37 · qhelium

In practice, the inverse applies. In the molecular range, the measured helium leak rate is approximately 2.7 times larger than the related air leak rate. If a helium leak detector tests to an air requirement, the inspector must know this factor. If not, the inspector rejects parts that meet the requirement.

From gas to liquid: capillary criterion

The literature contains no general conversion from gas leak rate to water leak rate. The reason is the flow physics: neither of the 2 laws for gas flow applies to liquids. Instead, a capillary criterion applies to the largest leak diameter that a liquid still holds back[2]:

dmax = 4 · σ · cos θ / Δp

In this equation, σ is the surface tension, θ the contact angle and Δp the pressure difference.

Numerical example at 0.3 MPa pressure difference and cos θ = 1: water does not pass through leaks with a diameter below approximately 1 µm[2]. Of the liquids in this source, refrigerants have the lowest surface tension. R134a has 8.1 mN/m, water 72.3 mN/m[2]. Thus, to the criterion, liquid R134a passes through all leaks above approximately 0.1 µm. It flows out through openings that water closes.

The same source gives a surface tension for AdBlue that is more than a factor of 50 below that of water[2]. This value is not plausible. AdBlue is an aqueous urea solution with 32.5 %. A manufacturer data sheet gives a surface tension of at least 65 mN/m at 20 °C[32]. This value is near the value of water.

Thus differences between aqueous media come mainly from the contact angle and from additives. Surfactants decrease the surface tension strongly, and the contact angle depends on the material[2].

Sequence in the test procedure. After a hydrostatic pressure test, the leak test does not find the leak. The liquid in the leak channel masks the leak[2]. Thus the leak test must be before the wet test.

Refrigerant loss as leak rate

For refrigeration and heat pump applications, the customer specification usually gives the requirement as mass loss per year. The conversion is:

q = (m / M) · R · T / t

For R134a, one source gives 7.6 · 10⁻⁶ mbar·l/s for 1 g per year[4]. A different source gives 6.5 · 10⁻⁶ mbar·l/s[1]. A recalculation with the values from the second source (molar mass 102.03 g/mol, 298 K) gives 7.7 · 10⁻⁶ mbar·l/s. The result supports the first value.

2 manufacturer compendia give values with 17 % difference for the same task. Recalculate constants from manufacturer documents before you use them in an acceptance criterion.

06

Calibration with the test leak

Each quantitative leak rate measurement needs a reference leak. ISO 20486 specifies its calibration and gives the characteristic values for practical use[14]:

Reference leaks to ISO 20486
PropertyPermeation leakCapillary leak
Temperature coefficient≈ 3.5 %/K≈ 0.3 %/K
Leak rate range10⁻¹⁰ to 10⁻⁴ Pa·m³/s> 10⁻⁷ Pa·m³/s

The temperature coefficients differ by one order of magnitude. This is the decisive selection criterion. A permeation leak in a hall without climate control has ± 17.5 % uncertainty at ± 5 K. This is more than the typical calibration uncertainty. The National Institute of Standards and Technology (NIST) independently confirms the order of magnitude: up to 4 % per K for helium permeation leaks[25].

ISO 20486 also gives requirements for the use of the leak. In practice, these requirements frequently get no attention[14]:

  • temperature equalisation at least 12 h before the measurement
  • warm-up time of the leak detector at least 2 h
  • for vacuum operation, at least 30 min of pump-down to remove accumulated tracer gas

The reference conditions are 20 °C and 1 000 mbar outlet pressure.

A manufacturer gives an expanded measurement uncertainty of ± 5.7 % at 95 % coverage probability for a calibrated helium leak at 23 °C. The tolerance band of the specification is ± 20 %. This gives a test uncertainty ratio of 3.5 to 1. The certificate is valid for at least 1 year. The leak rate decreases each year by a small percentage because the partial pressure difference to the environment decreases[26].

These leaks are traceable through the national metrology institutes. NIST calibrates leak standards from 1 · 10⁻⁶ to 1 · 10⁻¹³ mol/s, with temperature-dependent measurements over 0 to 50 °C[25].

07

Requirements in refrigeration and electronics cooling

Refrigeration and heat pumps: F-gas Regulation

Regulation (EU) 2024/573 came into force on 2024-03-11[27]. For operators and manufacturers of stationary refrigeration equipment, air-conditioning equipment and heat pumps, it specifies leak checks with graded intervals[28]. The threshold depends on the gas group. Gases in Annex I count in CO₂ equivalent, unsaturated hydrofluorocarbons in Annex II group 1 count in kilograms of charge.

Check intervals to Article 5 of Regulation (EU) 2024/573
Charge Annex ICharge Annex II group 1without leakage detectionwith leakage detection
from 5 t CO₂ equivalentfrom 1 kgcheck mandatorynot specified
below 50 t CO₂ equivalentbelow 10 kgevery 12 monthsevery 24 months
50 to 500 t CO₂ equivalent10 to 100 kgevery 6 monthsevery 12 months
from 500 t CO₂ equivalentfrom 100 kgevery 3 monthsevery 6 months

From 500 t CO₂ equivalent or from 100 kg of gas in Annex II group 1, a leakage detection system is mandatory. The system alerts the operator or a service company. The system must have a check at least every 12 months (Article 6)[28].

For the test bench design, this gives the result that follows: the check obligation does not depend only on the global warming potential. R1234yf has a global warming potential of 0.501 and is in Annex II group 1. Thus a facility with 1 kg of R1234yf or more needs checks[28]. Older mixtures in Annex I reach the threshold of 5 t CO₂ equivalent with only a few kilograms.

In series production of refrigeration and air-conditioning units, the target value is a refrigerant loss of 0.5 g per year. This is in the middle 10⁻⁶ range in standard cubic centimetres per second. As an illustration: approximately one bubble with 3 mm diameter under water every 1.2 h[29].

Liquid-cooled electronics

For cold plates, the Open Compute Project (OCP) requires a pressure decay test to EN 1779. The acceptance criterion is a pressure decay of less than 0.5 %. A bubble test in an immersion bath supplements the test. The OCP also requires a 5 min hydrostatic test at the maximum operating pressure. The burst test takes 2 min at 3 times the operating pressure[30].

The related requirements document compares 2 sets of rules. IEC 62368-1 requires leak tests at 3 times the normal operating pressure and at 2 times the pressure in the fault case. ASME B31.3 requires them at 1.5 times the design pressure[31].

Limits of the criterion “pressure decay less than 0.5 %”. Without test volume, test pressure, test time and temperature stability, it is not possible to convert the criterion into a leak rate. A pressure change of 0.5 % is in the same order of magnitude as a temperature drift of approximately 1.5 K[21], [22]. Thus a person who uses this criterion must also agree the temperature condition. Without this condition, the criterion also includes temperature changes of the environment.

08

Content of a leak tightness requirement

Sections 01 to 07 give a list of 7 data items. The list is a conclusion of Profectronics and not a requirement of a standard.

  1. Numerical value with unit and tracer gas. “10⁻⁸ mbar·l/s helium” and “10⁻⁸ mbar·l/s air” differ by a factor of 2.7 in the molecular range. In the laminar range, for example at 10⁻³ mbar·l/s, the factor is 1.08[2].
  2. Test pressure and pressure direction. Overpressure from the inside or vacuum from the outside changes the method and the result.
  3. Test time and stabilisation time. In the pressure decay method, these 2 times and the volume determine the detection limit.
  4. Temperature condition. Permitted drift during the test, in kelvin. Without this data, it is not possible to test a pressure decay requirement below approximately 10⁻² mbar·l/s[21].
  5. Reference temperature of the leak rate. 0 °C or 20 °C. The difference is 7 to 9 %[3].
  6. Calibration evidence. Type of test leak, calibration interval and temperature coefficient. For a permeation leak, the ambient temperature must be part of the test specification[14].
  7. Sequence in the test procedure. Leak test before each wet test[2].

On the selection of the method: for requirements below approximately 10⁻³ mbar·l/s, Profectronics does not recommend a pressure decay method. Between pressure-based and tracer gas methods, there are several decades. Longer test times do not close this gap. Only a different method closes it.

Validity: Research status August 2026. EN 1779 is in revision. The draft prEN 1779:2024 has 61 pages. The current edition of 1999 has 15 pages[5], [6]. Before you write a new test specification, examine the draft.

Profectronics builds test benches and does not certify. An accredited body makes the conformity assessment of a test specimen.

09

Sources

All references retrieved in August 2026, reference [32] in October 2026. For standards behind paywalls, the list gives the catalogue entries of the publishers. Numerical values from these standards come from preview versions that are freely accessible. Before a contractual use of these values, compare them with the original document.

  1. Leybold GmbH · Fundamentals of Leak Detection · 2024 · www.leybold.com/content/dam/brands/leybold/downloads/gated/Fundamentals-of-leak-detection-2024.pdf · manufacturer compendium
  2. Pfeiffer Vacuum · Compendium Leak Detection · retrieved 2026 · www.pfeiffervacuum.com/media/documents/leak-detection-know-how/leak-detection-compendium-pfeiffer-vacuum.pdf · manufacturer compendium
  3. ASTM International · ASTM E493/E493M-11(2022) · Standard Practice for Leaks Using the Mass Spectrometer Leak Detector in the Inside-Out Testing Mode · 2022 · store.astm.org/e0493_e0493m-11r22.html · standard
  4. INFICON · A Comprehensive Guide to Leak Detection — Leak Testing in the Automotive Industry · 2016 · www.inficon.com/media/7992/download/-Portals-0-PDF-ebooks-INFICON_E-Book_LeakTestingInTheAutomotiveIndustry_mika00en-b_1604.pdf · manufacturer compendium
  5. DIN Media · DIN EN 1779:1999-10 · Zerstörungsfreie Prüfung — Dichtheitsprüfung — Kriterien zur Auswahl von Prüfmethoden und -verfahren · 1999 · www.dinmedia.de/en/standard/din-en-1779/19709150 · standard
  6. DIN Media · DIN EN 1779:2024-12 (draft) · prEN 1779:2024 · 2024 · www.dinmedia.de/en/draft-standard/din-en-1779/384653977 · draft standard
  7. DIN Media · DIN EN 1593:1999-11 · Dichtheitsprüfung — Blasenprüfverfahren · 1999 · www.dinmedia.de/en/standard/din-en-1593/23304901 · standard
  8. DIN Media · DIN EN 13184:2001-07 · Dichtheitsprüfung — Druckänderungsverfahren · 2001 · www.dinmedia.de/en/standard/din-en-13184/38031246 · standard
  9. DIN Media · DIN EN 13185:2001-07 · Dichtheitsprüfung — Prüfgasverfahren (withdrawn) · 2001 · www.dinmedia.de/en/standard/din-en-13185/38031343 · standard, withdrawn
  10. DIN Media · DIN EN ISO 20485:2018-05 · Dichtheitsprüfung — Prüfgasverfahren · 2018 · www.dinmedia.de/en/standard/din-en-iso-20485/278805559 · standard
  11. BSI / ANSI Webstore · Preview BS EN ISO 20485:2018 (national and European foreword) · 2018 · webstore.ansi.org/preview-pages/BSI/preview_30334715.pdf · standard preview
  12. DIN Media · DIN EN 1330-8:1998-07 · Terminologie — Begriffe der Dichtheitsprüfung (withdrawn) · 1998 · www.dinmedia.de/en/standard/din-en-1330-8/5198490 · standard, withdrawn
  13. ISO · ISO 20484:2017 · Non-destructive testing — Leak testing — Vocabulary · 2017 · www.iso.org/standard/68188.html · standard
  14. ISO · ISO 20486:2017 · Non-destructive testing — Leak testing — Calibration of reference leaks for gases · 2017 · www.iso.org/standard/68191.html · standard
  15. ISO · ISO 18081:2024 · Acoustic emission testing — Leak detection by means of acoustic emission · 2024 · www.iso.org/standard/84936.html · standard
  16. ASTM International · ASTM E498/E498M-11(2022) · Standard Practice for Leaks Using the Mass Spectrometer Leak Detector or Residual Gas Analyzer in the Tracer Probe Mode · 2022 · store.astm.org/e0498_e0498m-11r22.html · standard
  17. ASTM International · ASTM E499/E499M-11 · Standard Practice for Leaks Using the Mass Spectrometer Leak Detector in the Detector Probe Mode · 2017 / 2025 · store.astm.org/e0499_e0499m-11r17.html · standard
  18. GlobalSpec / Engineering360 · ASTM E479 · Standard Guide for Preparation of a Leak Testing Specification — Status “Inactive” · retrieved 2026 · standards.globalspec.com/std/1731798/ASTM%20E479 · standard status
  19. M. Block (Sensistor Technologies) · Hydrogen as Tracer Gas for Leak Testing · ECNDT 2006 · www.ndt.net/article/ecndt2006/doc/Tu.2.6.1.pdf · conference paper
  20. ISO · ISO 3452-1:2021 · Non-destructive testing — Penetrant testing — Part 1: General principles · 2021 · www.iso.org/standard/75696.html · standard
  21. Dr. Wiesner Steuerungstechnik GmbH · Temperatureinfluss bei der Dichtheitsprüfung mit Druck · no year · www.drwiesner.de/fileadmin/user_upload/_imported/fileadmin/filestore-wiesner/doks/Temperatureinfluss.pdf · application report
  22. TetraTec Instruments GmbH · Dichtheitsprüfung — Vergleich Druckabfall- und Nachströmverfahren · no year · www.tetratec.de/wp-content/uploads/2025/03/Vergleich_Druckabfall_Nachstroemverfahren.pdf · application report
  23. Pfeiffer Vacuum GmbH · Possibilities and Limitations of Leak Testing Using Pressure Decay Methods · April 2024 · editoruploads.s3.juneapp.com/pfeiffervacuum/bf57da7b2a33677e571c04810c5dfde2.pdf · application report
  24. Nolek · The Pressure Decay Test Method · no year · www.nolek.com/wp-content/uploads/2015/11/The-Pressure-Decay-Test-Method.pdf · application report
  25. NIST · Leak Artifacts · retrieved 2026 · www.nist.gov/laboratories/tools-instruments/leak-artifacts · metrology institute
  26. Agilent Technologies · Calibrated Helium Leaks: Uncertainty, Tolerances, and Test Uncertainty Ratios, Doc. 5994-3020EN · 2021-04-15 · www.agilent.com/cs/library/technicaloverviews/public/techoverview-calibratedleak-hld-5994-3020en-agilent.pdf · manufacturer documentation
  27. EUR-Lex · Regulation (EU) 2024/573 on fluorinated greenhouse gases · 2024-02-07 · eur-lex.europa.eu/eli/reg/2024/573/oj/eng · legal act
  28. EUR-Lex · Regulation (EU) 2024/573 — full text, Official Journal L 2024/573 · 2024 · eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=OJ:L_202400573 · legal act
  29. J. McBee (Cincinnati Test Systems) · How to achieve accurate low leak rate testing · 2020-10-22 · www.cincinnati-test.com/blog/low-leak-rate-testing-refrigeration-air-conditioning-mfg · technical article
  30. Open Compute Project · White Paper: Cold Plate Development and Qualification · no date · www.opencompute.org/documents/ocp-cold-plate-development-and-qualification-with-integrated-comments-pdf · consortium specification
  31. Open Compute Project · ACS Liquid Cooling Cold Plate Requirements Document, Revision 1.0 · 2019-10-09 · www.opencompute.org/documents/ocp-acs-liquid-cooling-cold-plate-requirements-pdf · consortium specification
  32. BASF SE · Technical Leaflet AdBlue®, TI/M 6221e · April 2019 · chemicals.basf.com/dam/jcr:402f0ad1-7313-383f-a70a-cb24b834cf00/basf/chemicals/global/monomers/documents-/TDS_AdBlue_e.pdf · manufacturer data sheet
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