Carbon dioxide release determination quantifies the amount of CO2 emitted by materials, components, and products under controlled environmental conditions such as elevated temperature, humidity, and airflow. This analytical technique is widely used to evaluate thermal-oxidative degradation of polymers, verify the biodegradability of plastics, and characterize emissions that affect indoor air quality. Accredited third-party laboratories perform CO2 release determination in accordance with ISO, ASTM, EN, JIS, and GB standards, delivering accurate and repeatable results for research, quality control, and regulatory compliance.
Technical Overview
Carbon dioxide release determination is a laboratory analytical technique used to measure the quantity of carbon dioxide evolved from a test specimen when it is exposed to defined environmental conditions. Because carbon dioxide is one of the principal gaseous products of thermal-oxidative decomposition in organic materials, the amount of CO2 released serves as a sensitive and quantitative indicator of material degradation, oxidation, or microbial respiration.
During testing, the specimen is placed in a controlled environment—such as an aging oven, a glass reaction vessel, or an environmental emission chamber—with regulated temperature, relative humidity, and carrier gas flow. The released CO2 is captured and quantified using chemical absorption-titration, non-dispersive infrared (NDIR) analysis, gas chromatography, or continuous respirometric monitoring. Results are typically expressed as CO2 release per unit mass (mg/g or mg/kg), per unit surface area, as an emission rate over time, or as a percentage of theoretical carbon conversion in biodegradation studies.
CO2 release determination supports multiple engineering objectives: assessing the heat-aging resistance of automotive interior materials, validating antioxidant packages in polymers and elastomers, confirming the compostability of biodegradable plastics, and characterizing material contributions to indoor air CO2 levels. By correlating CO2 evolution with exposure time and temperature, engineers can model degradation kinetics and predict long-term material performance.
Testing Samples
CO2 release determination is applicable to a broad range of organic materials and finished products. Typical sample categories submitted to accredited third-party laboratories include:
- Thermoplastic polymers: polyethylene (PE), polypropylene (PP), ABS, polyamide (PA), polycarbonate (PC), polyoxymethylene (POM), and PVC compounds
- Rubbers and elastomers: EPDM, NBR, SBR, silicone rubber, thermoplastic elastomers (TPE/TPV)
- Polyurethane foams used in seating, headliners, and acoustic insulation
- Automotive interior trim components: instrument panels, door panels, pillar trims, steering wheel covers, and seat assemblies
- Textiles, nonwovens, leather, and synthetic leather materials
- Adhesives, sealants, potting compounds, and encapsulants for electronics
- Coatings, paints, powder coatings, and cured paint films
- Biodegradable and compostable plastics: PLA, PBAT, PBS, PHA, starch blends, and related packaging materials
- Building and interior decoration materials such as wood-based panels, laminates, and wallcoverings
- Lubricants, process oils, and polymer additives studied for oxidation stability
Testing Items
Depending on the client's objective and the applicable standard, the following parameters are commonly measured and reported:
- Total CO2 release quantity (mg CO2 per gram or kilogram of specimen)
- CO2 release rate under specified temperature and airflow conditions
- Cumulative CO2 evolution curve over the exposure period
- Degree of biodegradation expressed as percentage of theoretical CO2 (ThCO2) for composting and soil respiration studies
- CO2 emission rate per unit surface area (mg/(m2·h)) in chamber-based emission testing
- Comparative aging index: CO2 release of aged versus unaged specimens as an indicator of thermal-oxidative stability
- CO2 concentration contribution (ppm or mg/m3) under simulated indoor or in-vehicle environmental conditions
Testing Methods
Chemical Absorption-Titration Method
In this classical approach, the specimen is heated in an aging oven or tubular reactor while a stream of clean carrier gas (air, oxygen, or nitrogen) transports the evolved gases through an absorption train filled with barium hydroxide or sodium hydroxide solution. The absorbed CO2 is quantified by back-titration or precipitate gravimetry. This method is robust, requires inexpensive equipment, and remains widely used in heat-aging evaluation protocols for polymer and rubber materials.
Non-Dispersive Infrared (NDIR) Analysis
The effluent gas from the test chamber or reactor is directed through an NDIR CO2 sensor that measures infrared absorption at the characteristic CO2 wavelength. This technique enables continuous, real-time monitoring of CO2 concentration with high sensitivity and wide dynamic range, making it ideal for kinetic studies and automated respirometers used in controlled composting tests.
Gas Chromatography (GC) and GC-MS
Gas samples collected from the headspace or exhaust stream are analyzed by gas chromatography with thermal conductivity detection (TCD) or flame ionization detection following methanization. GC-MS confirmation can distinguish CO2 from other decomposition products, supporting comprehensive emission profiling when CO2 release is studied alongside VOC emissions.
Environmental Chamber (Emission Cell) Method
Following the principles of ISO 16000-9 and EN 16516, specimens are conditioned and placed in a climate-controlled emission chamber with defined temperature, relative humidity, air exchange rate, and loading factor. The steady-state or dynamic CO2 concentration in the chamber air is measured, allowing calculation of area-specific emission rates for indoor air quality and in-vehicle environment assessments.
Controlled Composting Respirometry
For biodegradability verification, the specimen is mixed with mature compost inoculum and incubated at 58°C in an aerobic reactor per ISO 14855-1, ASTM D5338, JIS K 6951, or GB/T 19277.1. Evolved CO2 is trapped in alkaline solution or measured continuously, and the cumulative CO2 is compared with the theoretical amount to calculate the degree of biodegradation. Soil-buried variants follow ISO 17556, ASTM D5988, or GB/T 22047.
Closed-Vessel Accumulation Method
The specimen is sealed in an inert airtight vessel maintained at constant temperature. CO2 accumulates in the headspace and is periodically sampled by gas syringe or automatic sampler for instrumental analysis. This method suits small sample quantities and long-duration stability screening.
Relevant Standards
- ISO 14855-1 / JIS K 6951 / GB/T 19277.1 - Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions by analysis of evolved carbon dioxide
- ASTM D5338 - Aerobic biodegradation of plastic materials under controlled composting conditions
- ISO 17556 / ASTM D5988 / GB/T 22047 - Aerobic biodegradation of plastics in soil
- EN 13432 - Packaging requirements for recoverable packaging by composting and biodegradation
- ISO 16000-9 / EN 16516 - Emission testing of building products using environmental chambers
- GB/T 18883 - Indoor air quality standard, including carbon dioxide limit values
- ASTM D6245 - Use of carbon dioxide concentrations in evaluating indoor air and ventilation conditions
Applications
- Automotive industry: evaluation of heat-aging resistance and low-emission performance of interior trim materials, foams, adhesives, and textiles
- Polymer research and development: screening of resin formulations, stabilization packages, and antioxidant systems based on oxidation-induced CO2 evolution
- Biodegradable plastics: certification support for compostable packaging, mulch films, and disposable products requiring demonstrated biodegradation levels
- Building and construction: assessment of decoration material contributions to indoor CO2 and overall emission profiles
- Electronics: stability evaluation of encapsulants, potting compounds, and conformal coatings exposed to thermal stress
- Quality control: batch-to-batch comparison of cured foams, rubber compounds, and coated components during production
- Academic and regulatory research: degradation kinetics modeling and shelf-life prediction based on CO2 evolution data
Testing Process
A typical CO2 release determination project follows a structured workflow designed to ensure traceability and repeatability:
- Sample receipt, registration, and conditioning under standardized temperature and humidity
- Confirmation of test conditions with the client, including exposure temperature, duration, atmosphere, and reporting units
- Preparation of the reaction system: reactor cleaning, carrier gas purification, and blank baseline measurement
- Exposure of the specimen with continuous or periodic capture of evolved CO2
- Quantitative analysis by titration, NDIR, or chromatographic instrumentation with calibration against certified reference gases
- Data processing, blank correction, and calculation of release quantity, rate, or biodegradation percentage
- Issuance of a formal test report including methods, conditions, results, and instrument calibration information
FAQ
What sample size and form are required?
Specimens are usually supplied as granules, cut pieces, films, cured plaques, or finished components. Chemical absorption and biodegradation methods generally require several grams of material, while chamber emission methods evaluate finished parts or defined surface areas. Laboratories can advise on cutting, grinding, or conditioning requirements before testing begins.
How long does CO2 release determination take?
Aging-based CO2 release tests under oven conditions are commonly completed within 3 to 10 working days plus analysis time. Controlled composting biodegradation studies require continuous incubation over several weeks to months until the plateau phase is reached. Specific schedules depend on the standard and end point selected.
In what units are the results reported?
Results may be reported as mg CO2 per gram of specimen, mg CO2 per kilogram, area-specific emission rates in mg/(m2·h), headspace concentration in ppm or mg/m3, or as percentage degree of biodegradation relative to theoretical CO2, depending on the test protocol.
How is CO2 release determination different from VOC emission testing?
VOC emission testing targets volatile organic compounds such as aldehydes, aromatics, and hydrocarbons, whereas CO2 release determination specifically quantifies carbon dioxide as a marker of oxidation or mineralization. The two tests are complementary and are frequently combined to fully characterize the emission behavior of a material under heat and aging.
What factors influence the test results?
Temperature, oxygen availability, relative humidity, specimen surface-to-mass ratio, aging pre-history, and carrier gas flow rate all affect the measured CO2 release. Standardized conditioning and strict control of these parameters are essential for valid interlaboratory comparison.
Can testing be performed under customized conditions?
Yes. Accredited third-party laboratories routinely design tailor-made protocols with client-specified temperatures, exposure durations, atmospheres, and acceptance criteria to support development programs and supplier specifications in addition to standardized methods.