GMW 15634 Determination of Volatile and Semi-Volatile Organic Compounds in Vehicle Interior Materials

The “GMW 15634 Determination of Volatile and Semi-Volatile Organic Compounds from Vehicle Interior Materials” standard, developed by General Motors Worldwide (GMW), is an engineering standard used to determine volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) emitted from vehicle interior materials. This standard is particularly important for evaluating the emission behavior of materials used in automotive cabins.

Automotive interior materials can release small amounts of chemicals into the cabin air. These emissions may result from:

• Plastics and polymers
• foams
• Adhesives
• Coatings
• Textile
• Leather and synthetic leather
• Movies
• Composite materials
• Other non-metallic internal components

The GMW 15634 standard provides a standardized method for identifying and semi-quantitating these emissions. The aim is to help manufacturers control indoor air quality and prevent excessive concentrations of undesirable substances.

The GMW 15634 standard focuses primarily on two emission categories:

• Volatile organic compounds (VOCs): These are relatively volatile organic substances that can evaporate from materials and enter the vehicle cabin atmosphere. Examples include:
  • Benzene
  • Toluene
  • Ethylbenzene
  • Xylene
  • styrene

The standard for material approval specifically identifies restricted compounds such as BTEX and styrene: concentrations of 1 ppm or higher require measurement under Method A.

• Semi-volatile organic compounds (SVOCs): These are less volatile than volatile organic compounds. They can condense on relatively cool surfaces inside the vehicle, such as glass, instrument panel surfaces, or plastic lenses. The GMW 15634 standard defines total SVOCs using a chromatographic range corresponding approximately to n-C16 to n-C32. Total VOCs are defined using a chromatographic range up to n-C20.

The tests utilize the GMW 15634 standard thermal desorption-gas chromatography/mass selective detection (TD-GC/MSD). The basic principle is as follows: automotive material, controlled heating, released organic compounds, collection, thermal desorption, GC/MS analysis, identification, and semi-quantification. The material sample is heated under controlled conditions to release volatile and semi-volatile substances. The released compounds are collected and then fed into a gas chromatograph/mass spectrometer for analysis. For VOC analysis, samples are heated to approximately 90 degrees, and for SVOC analysis to 120 degrees, followed by thermal desorption and GC/MS analysis.

The GMW 15634 standard includes two analytical approaches:

• Method A Material Approval: This method is used for routine material approval and determination of total VOC/SVOC as well as specified restricted compounds. It is the primary method for demonstrating compliance with applicable requirements for automotive interior materials.
• Method B Problem solving / detailed identification: This method can be used when additional compounds need to be identified, particularly those not included in the restricted substance list. This makes Method B useful for addressing unusual emission results and determining the source of an unexpected emission peak.

A typical GMW 15634 laboratory setup includes the following:

• Thermal desorption equipment
• Controlled temperature heating system
• Adsorbent/sample tubes
• Gas chromatography (GC)
• Mass selective detector (MSD)
• Carrier gas supply
• Calibration / reference compounds
• Data processing and chromatographic analysis software.

The use of GC/MS allows for the identification of individual organic compounds from their characteristic retention times and mass spectra.

In general, the testing procedure follows these steps:

• The sample is prepared according to the standard.
• The sample is placed in a thermal desorption system.
• The sample is heated under the specified VOC conditions.
• Organic compounds released from the material are collected.
• The collected compounds are desorbed thermally.
• The compounds are transferred to the GC/MSD system.
• The identified compounds are described.
• VOC emissions and related restricted substances are identified.
• SVOC analysis is performed under the specified conditions.
• Analytical results are reported and compared with relevant material requirements.

The actual dimensions, mass, heating conditions, calibration, and reporting requirements of the sample are specified in the GMW 15634 standard.

This standard uses reference substances for semi-quantitative assessment. For example, toluene is defined as a reference for VOC assessment and n-hexadecane is defined as a reference for SVOC assessment. This allows the laboratory to consistently express results and compare emissions from different materials.

The GMW 15634 standard is important because vehicle occupants spend a significant amount of time in the passenger compartment. Therefore, interior materials should not release excessive amounts of undesirable organic compounds. This standard helps to:

• Controlling indoor material emissions.
• Identifying potentially undesirable volatile organic compounds (VOCs).
• To assess semi-volatile organic compound (SVOC) emissions.
• Comparing different material formulations
• Supporting material approval
• Investigating emission-related problems.
• Improving in-vehicle air quality.
• To provide reproducible laboratory data for suppliers and General Motors.

The GMW 15634 standard is part of a broader family of automotive interior emissions test methods. Laboratories often list this standard alongside others such as VDA 278, GMW 15635, GMW 3205, and GMW 3235.

The GMW 15634 standard is closely related to the VDA 278 standard approach because it uses thermal desorption and GC/MS techniques to characterize organic emissions from non-metallic automotive materials. However, they should not be considered automatically interchangeable. The GMW 15634 standard includes General Motors-specific requirements, including definitions, restricted substances, and assessment procedures.

The GMW 15634 standard is applicable to many types of interior vehicle materials, including:

• Plastics: VOC/SVOC emissions
• Foams: Chemical emissions
• Synthetic leather: VOC and SVOC assessment.
• Leather: Interior emissions
• Textiles: Organic emissions
• Adhesives: Emission screening
• Coatings: VOC/SVOC assessment
• Films: Emission behavior
• Composite materials: Material approval
• Interior components: General emission characterization

Testing laboratories currently list the GMW 15634 standard for materials such as plastics, elastomers, films, textiles, leather, coated textiles, composites, and foams.

In conclusion, the GMW 15634 standard allows laboratories to identify and semi-quantify VOC and SVOC emissions using GC/MS analysis following thermal desorption.

The main value of this standard is not only to measure the total amount of emissions, but also to identify individual compounds and control restricted substances that may affect the quality of the vehicle interior environment. For suppliers of plastics, foams, textiles, leather, coatings, adhesives and other interior materials, compliance with the GMW 15634 standard requirements is a crucial part of the material approval process.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services in accordance with the GMW 15634 standard.