OTR: What Oxygen Transmission Rate Is and How It Is Measured

Oxygen transmission rate (OTR) is an important parameter for evaluating the barrier properties of films and packaging materials. It describes how much oxygen passes through a material over a specified area and period under defined test conditions.

OTR measurements help manufacturers, packaging developers and laboratories compare materials, assess oxygen barrier performance and support material selection, product development and quality control.

Understanding what OTR means, how it is measured and which factors influence the result is essential when evaluating materials intended to control oxygen transmission.

What Is Oxygen Transmission Rate (OTR)?

Oxygen transmission rate is the amount of oxygen that passes through a defined area of a material over a given period under specified test conditions.

OTR is commonly used to characterize plastic films, laminates, coatings and other packaging materials where oxygen transmission needs to be evaluated.

The reported value depends not only on the material but also on the measurement conditions, including temperature and, where relevant, relative humidity and the oxygen pressure difference across the sample.

OTR is therefore most useful when the test conditions and reporting units are clearly specified.

Why Is OTR Important?

Oxygen can affect products that are sensitive to oxidation or changes in their surrounding atmosphere. Measuring OTR helps evaluate the oxygen barrier properties of packaging materials and compare alternative material options.

Packaging Development

During packaging development, OTR measurements can help compare different films, coatings and multilayer structures. The results provide information about their oxygen transmission behavior under defined conditions.

Material Selection

OTR data can support the selection of materials for applications where oxygen transmission is an important consideration. The required barrier performance depends on the product, packaging design and intended conditions of use.

Quality Control

Consistent OTR testing can help laboratories monitor material performance and investigate differences between samples or production batches.

Research and Optimization

Manufacturers and material developers can use OTR measurements to investigate how material composition, thickness and structure influence oxygen transmission.

An OTR result is one part of a broader packaging evaluation and should be interpreted alongside other relevant material properties and application requirements.

How Is OTR Measured?

OTR testing measures oxygen transmission through a material under defined conditions. The procedure depends on the selected test method, the material being tested and the measurement system.

In a typical film measurement, a sample is mounted between two chambers. One side is exposed to oxygen or a gas mixture containing a defined oxygen concentration, while the other side is used to detect or measure the oxygen that passes through the sample.

The measurement system records the transmission behavior over time and determines the OTR according to its measurement principle and the applicable method.

The exact apparatus, detection technique, test sequence and calculation procedure depend on the instrument and method used. Laboratories should follow the relevant operating instructions and test procedure rather than assuming that all OTR systems work identically.

Sample Preparation

Correct sample preparation is important for obtaining meaningful results.

Before testing, laboratories should consider:

• Whether the sample represents the material being evaluated.
• Whether the film thickness has been documented where required.
• Whether the sample contains folds, punctures or other visible defects.
• Whether the sample dimensions are suitable for the instrument.
• Whether the mounting and sealing procedure is correct.
• Whether any conditioning procedure is required by the selected method.

Inadequate sealing can allow oxygen to bypass the material, potentially affecting the result.

Test Conditions

OTR depends on the conditions under which the measurement is performed. Important factors include:

Temperature: oxygen transmission behavior can change with temperature, so the test temperature should be defined and controlled as required.

Relative humidity: humidity may influence the barrier properties of some materials, especially moisture-sensitive films and multilayer structures.

Oxygen conditions: the oxygen concentration and pressure conditions specified by the method influence the driving force for transmission.

Sample thickness and structure: thickness and the composition of the film should be recorded where relevant to the method and the intended comparison.

Measurement range: the instrument should be suitable for the expected oxygen transmission values.

Documenting these conditions helps laboratories interpret results and compare measurements obtained at different times.

What Units Are Used for OTR?

OTR is generally expressed as the volume of oxygen passing through a unit area of material over a specified period. Common reporting conventions include units such as:

• cm³/(m²·day)
• cm³/(m²·24 h)

The exact unit and reference conditions depend on the test method and reporting convention.

When comparing OTR values, check that the units and test conditions are equivalent. A numerical value cannot be interpreted correctly without understanding the conditions under which it was measured.

What Is the Difference Between OTR and Oxygen Permeability?

OTR and oxygen permeability are related, but they are not the same quantity.

OTR describes the oxygen transmission rate through a material under specified test conditions. It is commonly used to compare the oxygen barrier performance of packaging films.

Oxygen permeability describes a material property associated with the transport of oxygen through the material. A permeability coefficient accounts for the driving force for transport and material thickness according to the calculation method used.

OTR is affected by the film thickness and test conditions. A permeability coefficient is intended to characterize the material’s transport behavior while accounting for the relevant thickness and driving force.

The two values should not be compared directly without considering their definitions, units and calculation methods.

For more information, see Oxygen Permeability and OTR: Measurement and Analysis.

Which Factors Affect OTR?

Several material and testing factors can influence the measured oxygen transmission rate.

Material Composition

Different polymers and barrier materials interact with oxygen in different ways. Their chemical structure and physical properties influence how readily oxygen can move through the material.

Film Thickness

Thickness affects the distance oxygen must travel through the material. However, thickness alone does not determine OTR, and materials should be compared under consistent conditions.

Multilayer Structures

Films may combine multiple layers to achieve a particular balance of barrier and other functional properties. The overall OTR depends on the complete structure, not simply on the properties of one individual layer.

Learn more in [Permeability Testing of Multilayer Films and Laminates].

Temperature and Humidity

Temperature can affect oxygen transmission, while humidity can influence materials that are sensitive to moisture. Consistent test conditions are important for reliable comparisons.

Sample Integrity and Sealing

Damage to the film or leakage around the sample can affect the measurement. Proper inspection, preparation and mounting are therefore important parts of the test procedure.

Measurement Method

Different test methods and conditions may produce results that are not directly comparable. The method, instrument configuration and reporting units should be considered when reviewing data.

La misura OTR può essere utilizzata in diverse fasi del ciclo di sviluppo e produzione di un materiale.

In particolare, permette di:

• confrontare differenti film;
• valutare materiali barriera;
• ottimizzare strutture multistrato;
• verificare l’effetto di variazioni di composizione o spessore;
• qualificare materiali e fornitori;
• controllare la costanza delle prestazioni;
• supportare ricerca e sviluppo.

Il valore OTR diventa quindi un parametro quantitativo utile per caratterizzare e confrontare il comportamento dei materiali nei confronti dell’ossigeno.

How Should OTR Results Be Interpreted?

OTR results provide information about oxygen transmission through a material under specified conditions.

For otherwise comparable samples tested using the same method and conditions, a lower OTR generally indicates a lower oxygen transmission rate and therefore stronger resistance to oxygen passage.

However, an OTR value should not be interpreted in isolation. Its significance depends on the intended application, the product being packaged and the relevant performance requirements.

When comparing results, check:

• The reported OTR value and units.
• The test temperature and relative humidity.
• The oxygen conditions used during the measurement.
• The film thickness and structure.
• The test method and instrument configuration.
• Whether the samples were prepared and tested consistently.

A result obtained for a flat film sample does not automatically describe the oxygen barrier performance of an entire finished package, which may also include seals, closures and other components.

OTR Testing in Packaging Applications

OTR testing is used to characterize oxygen barrier properties in different packaging materials and structures.

Food Packaging

For food packaging, oxygen transmission can be an important consideration when evaluating materials intended to protect product quality. OTR measurements help compare candidate materials under defined test conditions.

Explore Permeability Testing for Food Packaging.

Plastic Films

OTR testing can be used to characterize and compare plastic films with different compositions, thicknesses and structures.

Explore Permeability Testing of Plastic Films.

Flexible Packaging

Flexible packaging may contain films, coatings, laminates and multilayer structures. OTR testing can help evaluate the oxygen barrier performance of the selected material structure.

Explore Permeability Testing of Flexible Packaging.

Pharmaceutical Packaging

For pharmaceutical packaging, OTR measurements may contribute to the characterization of materials where oxygen transmission is relevant. The appropriate evaluation depends on the product and packaging system.

A permeability measurement alone does not establish product safety or regulatory compliance.

How to Choose an OTR Tester

Selecting an OTR testing system starts with defining the measurement requirements and the materials to be tested.

Consider the following factors:

• Measurement range: the expected oxygen transmission values.
• Sample characteristics: material type, thickness and structure.
• Test conditions: required temperature and relative humidity.
• Test method: the procedure and reporting requirements applicable to the material.
• Laboratory workflow: the number of samples and data handling requirements.
• Additional parameters: whether water vapor or carbon dioxide transmission also needs to be measured.

If several transmission parameters are required, a system that supports multiple measurements may help consolidate laboratory testing. Compatibility with the actual samples and test method should always be confirmed before selecting an instrument.

ExtraSolution Instruments for OTR Testing

ExtraSolution offers solutions for measuring oxygen transmission rate alongside other barrier parameters, depending on the instrument model.

MultiPerm O2-CO2

Designed for oxygen transmission rate (OTR) and carbon dioxide transmission rate (CO₂TR) measurements.

Explore MultiPerm O2-CO2.

MultiPerm O2-H2O

Designed for oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) measurements.

Explore MultiPerm O2-H2O.

TotalPerm

Combines OTR, CO₂TR and WVTR measurement capabilities in one integrated system.

Explore TotalPerm.

The appropriate system depends on the sample, required measurement range, test conditions and applicable method. Contact ExtraSolution to discuss your OTR testing requirements and confirm instrument suitability.

Conclusion

Oxygen transmission rate is a key parameter for evaluating the oxygen barrier performance of films and packaging materials. Measuring OTR under defined conditions helps laboratories compare materials, support packaging development and monitor material performance.

Correct sample preparation, suitable test conditions and careful interpretation of the reported units are essential for meaningful comparisons.

ExtraSolution provides solutions for measuring oxygen transmission through films and barrier materials.

Contact ExtraSolution to discuss your OTR measurement requirements and identify a suitable testing solution.

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