The Importance of Vehicle Indoor Air Quality

The coveted “new car smell” is now known to result from chemicals emitted from plastic and leather parts that make up the interior of automobiles. These parts emit volatile organic compounds (VOCs; e.g., benzene, formaldehyde), semi-volatile organic compounds (SVOCs; e.g., phthalates, trichlorophenyl phosphate [TCPP]), and other chemicals. For example, TCPP is a flame retardant often found in polyurethane foams. Although TCPP provides safety by reducing the risk of these foams igniting in a fire or accident, its semi-volatile nature causes it to release into the car’s interior, where passengers can be exposed to its vapor.

VOCs and SVOC affect vehicle interior air quality, or VIAQ. Unfortunately, substantial harms to human health have been linked to interior parts off-gassing VOCs and SVOCs. The confined space of the passenger compartment allows these chemicals to concentrate, reaching levels that may negatively affect human health. Furthermore, heat and ultraviolet light can trigger the additional release of these chemicals, making the risk of exposure to dangerous concentrations of VOCs and SVOCs greatest in the summer, when car interiors can get as hot at 192°F (88°C).1 The breathing of polluted air and cause throat irritation, severe health effects such as asthma and COPD, and an increased risk of cardiovascular issues.2 While this information has been well linked to indoor air quality in buildings (e.g., Sick Building Syndrome), the quality of vehicle indoor air has been comparably overlooked until more recently. Many individuals often spend up to 3 hours per day in their cars. Thus, despite previously escaping scrutiny, designers and producers of this indoor environment are now under growing pressure to improve and regulate VOC and SVOC emission from interior car parts. The accurate analysis of off-gassed VOCs and SVOCs from interior car parts represents an important quality control issue for automotive companies.

The VOCs commonly off-gassed in vehicle interiors that have the greatest potential toxicity to humans include: benzene and formaldehyde (classified by the International Agency for Research on Cancer (IARC) as Group 1 carcinogens), ethyl benzene and styrene (IARC Group 2B carcinogens), and other molecules, such as toluene, xylene, and acetaldehyde. Within the passenger compartment of a new vehicle, the concentration of each of these compounds often exceed the levels deemed safe for extended human exposure.3

Vehicle interior air quality (VIAQ) standards vary widely in different regions of the world, and regulations or voluntary standards on the permissible concentrations of VOC in new vehicles have only been adopted in a handful of countries. Currently, only Russia, Japan, South Korea, and China have national regulations, but next year, changes in the Chinese, European, and U.S. regulations will tighten restriction on vehicle indoor air emissions.4

Currently, automobile manufacturers seem to contend with these regional differences in regulations by making concessions in markets with the tightest requirements, and using their own standards with cars sold in the rest of the world. For example, BMW provides PM 2.5 filters in all its cars sold in China, where consumers are more sensitive to odors. Notably, BMW feels that it cannot change the odor universally through product development without complaints from other markets, leading them to adopt this customization. However, BMW is pushing for a global standard for vehicle indoor air emissions because a global rule would standardize testing and save time.4

GERSTEL’s customers in the automotive industry are using GERSTEL products to evaluate VOCs and SVOC s that are off-gassed by interior parts of cars. These materials vary widely and include plastics used for the dashboard, carpet on the floor, foam moldings in the door panels, and more. To measure the VOCs and SVOCs emitted by interior car parts, the parts are placed in sample bags for environmental chamber testing. The concentrations of VOCs and SVOCs can be measured by gas chromatography mass spectrometry (GC/MS). Emissions can be measured over time or upon exposure to heat or ultraviolet radiation (simulating the interior vehicle conditions experienced on hot, summer days when cars are parked in direct sunlight).

Thermal desorption instruments enable more accurate and quantitative analysis of VOCs and SVOCs from a sample material. GERSTEL created their first Thermal Desorption Unit for use with the VDA 278 method, which is used by vehicle manufactures to test for VOC emissions and fogging compounds. The GERSTEL TDS was developed to solve a VIAQ problem:  the fogging of windshields due to the emissions of SVOC’s from the polymers in the dashboard.  The VDA 278 method is based on direct thermal extraction, wherein the desorption temperature is the most critical method parameter for successful extraction. The GERSTEL Thermal Desorption System (TDS), fitted with a GERSTEL TDSA Autosampler, allows for precise control of extraction temperature and automated workflow from sample extraction to analysis, thereby maximizing efficiency and producing accurate, reproducible results.5 Importantly, this system can be used for VOC and FOG analysis, the latter of which examines condensable organic compounds that create the “fogging effect.”  TDS/TDSA systems are regularly used in VDA “round robin” testing to ensure industry-wide compliance with automotive specifications.

Recently, Ford Motor Company has partnered with GERSTEL to use the GERSTEL Dynamic Headspace Station and GERSTEL Thermal Desorption Unit (TDU)to measure semi-volatile emissions from foams and other automotive parts. Vehicle testing at Ford includes measuring VOC and SVOC concentrations in various conditions: indoors or outdoors and with windows open or closed. They capture both standing emissions (exhaust) and compounds off-gassed by interior parts. Samples are heated in sampling bags for 2 hours at 65°C before processing through thermal desorption-GC/MS to analyze VOC. These offerings help Ford, and indeed the International Standards Organization as well, to develop optimized, standardizable, testing methods that can be used to ensure compliance with the changing and developing VIAQ regulations.

In addition to this specific example, GERSTEL has several other products that can improve the reliability, speed, and accuracy of VIAQ analysis. For example, the analysis of airborne aldehydes and ketones requires the collection of these analytes by passing them through 2,4-dinitrophenylhydrazine (DNPH). GERSTEL MultiPurpose Sampler MPS Robotic can be configured with a special tray to hold DNPH cartridges, with improves the automation of online desorption and analysis of DNPH derivatives. Using the  GERSTEL MultiPurpose Sampler MPS Robotic, fitted with the DNPH cartridge and coupled to an Agilent 6460 Triple Quadrupole Mass Spectrometer, the measurement of VOCs and SVOCs from car interior air samples can be analyzed reliably and reproducibly in samples collected using a hand-held air sampler. Importantly, this process can be fully automated. 5

Finally, thermal extraction using the GERSTEL Thermal Extractor (TE) offers an efficient alternative to environmental chamber testing for VOCs and SVOCs in interior spaces in buildings and vehicles, and this approach had been adopted and optimized in the EU, where an AgBB evaluation scheme is used to monitor VIAQ. The large extraction tube of the TE (ID: 14 mm, length of heated zone: 75 mm) can be loaded with much larger and more representative samples than regular thermal desorption tubes. The samples are heated in a flow of inert gas, and the extracted analytes are purged onto an adsorbent tube and concentrated. Thermal Desorption-GC/MS analysis is subsequently performed following the AgBB guidelines. Thermal extraction offers and easier and less costly means to obtain reliable, consistent information on indoor air quality, and it is easily adaptable for VIAQ.6,7

In conclusion, the analysis and control of VIAQ is an important consideration for human health. Vehicle interiors that comply with current and future regulations for vehicle indoor air emissions will be essential to the automotive market. Analysis of VOCs and SVOCs using GC/MS coupled to the GERSTEL Thermal Desorption Unit (TDU) , GERSTEL MultiPurpose Sampler MPS Robotic, and other GERSTEL products will help to ensure automated, reliable, and consistent results, which will be essential for the compliance of automotive companies with the new and evolving regulations.