Tracking Wood Emissions with Gas Chromatography: How Heat Treatment Changes Indoor Air Pollutants

Although thermal modification is commonly used to improve the durability and dimensional stability of wood, the modification alters the emission profile of volatile organic compounds (VOCs), which might influence indoor air quality. A study conducted by researchers at the Technical University in Zvolen (Slovakia) evaluated the effect of accelerated aging on VOC emissions from thermally modified Norway spruce (Picea abies) wood, with untreated and thermally treated samples (160, 180, and 210 °C) subjected to accelerated aging in a xenon test chamber for 600 h. The VOCs emitted were analyzed using headspace gas chromatography-mass spectrometry (HS-GC-MS). A paper based on this work was published in Materials.¹

Primarily used to improve its dimensional stability under varying moisture conditions, thermal processing represents a well-established commercial technology that enhances the appearance, dimensional stability, and durability of wood.² Compared to other modification methods, its advantage is the absence of additional chemicals that could negatively affect the environment or the ecological quality of wood products.^3-5 There is an increase in attention concerning gases released from heat-treated wood; since this wood is often used indoors, it is important to understand how it might affect air quality and safety. This matters even more because some harmful chemicals have been found in certain types of treated wood like pine and poplar.⁶ 

The research revealed that thermal modification significantly reduced total VOC compared to untreated wood, with samples treated at 210 °C showing up to a 376-fold decrease. Increasing modification temperature reduced the amount and variability of emitted VOCs and altered their chemical composition. Terpenes (aromatic compounds found in many plants)⁷ dominated in untreated wood, particularly α-pinene (51%), whereas thermally treated samples showed lower terpene content and higher proportions of carbonyl compounds such as furfural. Accelerated aging further affected VOC emissions, including a 42% decrease in TVOC for the 160 °C sample and compositional shifts characterized by the disappearance or formation of specific compounds.¹

From a practical perspective, write the authors of the paper,¹ “the results indicate that thermal modification can serve as an effective approach to reduce VOC emissions from spruce wood intended for indoor applications. The findings suggest that higher modification temperatures significantly decrease total VOC emissions, which may help optimize thermal treatment parameters during the production of low-emission wood materials. In addition, the obtained emission data may provide useful input for quality control procedures and for supporting environmental product declarations or other emission evaluation frameworks applied to wood-based products.”

“Future research,” the authors continue,¹ “should focus on the long-term emission behavior of thermally modified wood under real indoor environmental conditions, including the influence of humidity, temperature fluctuations, and natural light exposure. Further studies could also investigate the effect of different thermal treatment durations and regimes on VOC formation and stability. In addition, expanding the research to other wood species would provide a broader understanding of VOC emission mechanisms and support the development of practical guidelines for optimizing thermal treatment parameters to minimize VOC emissions.”

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References

1. Bubeníková, T.; Kačík, F.; Darabošová, A. et al. Accelerated Aging Effect on Volatile Organic Compound Emissions from Thermally Treated Spruce Wood. Materials (Basel) 2026, 19 (6), 1135. DOI: 10.3390/ma19061135
2. Westin, M.; Simonson, R.; Östman, B. Kraft Lignin Wood Fiberboards—The Effect of Kraft Lignin Addition to Wood Chips or Board Pulp Prior to Fiberboard Production. Holz Roh Werkst. 2001, 58, 393–400. DOI: 10.1007/s001070050451
3. Júda, M.; Sydor, M.; Rogoziński, T. et al. Effect of Low-Thermal Treatment on the Particle Size Distribution in Wood Dust after Milling. Polymers (Basel) 2023, 15 (4), 1059. DOI: 10.3390/polym15041059
4. Navi, P.; Sandberg, D. Thermo-Hydro-Mechanical Wood Processing; EPFL Press, 2012.
5. Sandberg, D.; Haller, P.; Navi, P. Thermo-Hydro and Thermo-Hydro-Mechanical Wood Processing: An Opportunity for Future Environmentally Friendly Wood Products. Wood Mater. Sci. Eng. 2013, 8, 64–88. 10.1080/17480272.2012.751935
6. Kamdem, P.; Pizzi, A. P.; Jermannaud, A. Durability of Heat-Treated Wood. Holz Roh Werkst. 2002, 60, 1–6. DOI: 10.1007/s00107-001-0261-1
7. What to Know About Terpenes. Medical News Today website.https://www.medicalnewstoday.com/articles/what-are-terpenes (accessed 2026-04-03)