###### Abstract  
In this study, headspace-bar adsorptive microextraction (HS-BA\(\upmu\)E) combined with gas chromatography-mass spectrometry (GC-MS) was employed to screen the major biogenic volatile organic compounds (BVOCs) emitted by six different Portuguese shrub species (_Erica scoraria_ L., _Cistus ladanifer_ L., _Cistus nonspaliensis_ L., _Larandula stocchas_ L., _Thymus villosus_ L., and _Thymus camphoratus_). The HS-BA\(\upmu\)E/GC-MS methodology was developed, optimized, and validated using five common monotereponids (\(\upalpha\)-pinene, \(\upbeta\)-pinene, limonene, 1,8-cineole, and thymol) and one sesquiterpenoid (caryophyllene oxide). Under optimized experimental conditions (microextraction-sorbent phase: activated carbon (CN1), 3 h (35 \({}^{\circ}\)C); back-extraction: _n_-C\({}_{6}\) (1 h)), good efficiencies (>45%), low analytical thresholds (5.0-15.0 \(\upmu\)g/L) and suitable linear dynamic ranges (20.0-120.0 \(\upmu\)g/L, r\({}^{2}\) > 0.9872) were achieved, as well as acceptable intra and inter-day precisions (RSD \(\leq\) 30.1%). Benchmarking the proposed methodology, HS-BA\(\upmu\)E(CN1), against the reference methodology, HS-SPME(PDMS/DVB), revealed comparable analytical responses and demonstrated excellent reproducibility. Among the six shrub species studied, _Thymus camphoratus_ exhibited the highest emissions of BVOCs from its leaves, notably, 1,8-cineole (4136.9 \(\pm\) 6.3 \(\upmu\)g/g), \(\upalpha\)-pinene (763.9 \(\pm\) 0.5 \(\upmu\)g/g), and \(\upbeta\)-pinene (259.3 \(\pm\) 0.5 \(\upmu\)g/g). It was also the only species found to release cryophyllene oxide (411.4 \(\pm\) 0.3 \(\upmu\)g/g). The observed levels suggest that these shrub species could potentially serve as fuel sources in the event of forest fires occurring under extreme conditions. In summary, the proposed methodology proved to be a favorable analytical alternative for screening BVOCs in plants. It not only exhibited remarkable performance but also demonstrated user- and eco-friendliness, cost-effectiveness, and ease of implementation. B 2024 11 264 11 264 1  
of forest fires. This phenomenon has contributed to catastrophic events like the one in Pedrogao Grande, Portugal. Since these BVOCs have lower densities than air, they tend to accumulate at lower altitudes, underscoring the importance of studying shrubs, which are small-to-medium-sized perennial woody plants. Moreover, under specific weather conditions (temperature \(\geq\) 30 \({}^{\circ}\)C, 30 consecutive days without rain, relative air humidity \(\leq\) 30%, and wind speeds exceeding 30 km/h) known as the 'rule of 30', the terpenoids emitted can intensify ignition, accelerating the spread of fires. In recent years, Portugal has experienced a significant number of forest fires, with approximately 3 million hectares burned between 1980 and 2020, equivalent to around one-third of its territory. Consequently, it is imperative to study the characteristics of BVOCs emitted by some of the most common shrubs, especially in the Mediterranean region, which is marked as one of the most susceptible areas to forest fires due to its climatic conditions characterized by regular periods of high temperatures and drought [3]. The state-of-the-art analytical methodologies for monitoring BVOCs emitted by plants typically involve an enrichment step prior to analysis by gas chromatography-mass spectrometry (GC-MS) [4; 5; 6; 7; 8]. Currently, one of the most used non-exhaustive techniques for BVOC monitoring is solid phase microextraction (SPME), particularly in the headspace (HS) mode, which is applicable to liquid, solid, and _in situ/in vivo_ matrices [4; 9; 10]. SPME uses selective and sensitive fibers and operates in a single step, meeting the principles of green analytical chemistry (GAC) by being a solvent-free approach [11]. However, there is a need for alternative analytical methods for HS monitoring of compounds that are user- and eco-friendly, cost-effective, and easy to implement.