Particulate matter (PM) is a major health risk, particularly in indoor environments where air quality should be optimized and pollution reduced efficiently. While technical air purification systems can be costly and impractical, indoor plants offer a sustainable alternative. Using a novel methodology, four common indoor plants were evaluated for their potential to reduce PM_2.5. PM_2.5 was introduced via incense in a custom-designed test chamber with air circulating at 0.3 m/s. Air quality was continuously monitored with an AirGradient Open Air device (Model O-1PST), an optical particle counter. Statistical significance was confirmed by independent t-tests and ANOVA. Calcium chloride regulated relative humidity in the chamber. The plants Epipremnum aureum, Chlorophytum comosum, Nephrolepis exaltata, and Maranta leuconeura were assessed for their PM_2.5-binding capacity. Nephrolepis exaltata showed the highest reduction efficiency. Maranta leuconeura with its hemispherical leaf cells was tested for the first time and proved to trap particles within its leaf structure. It is ranked second and showed a stronger dependence on ambient PM_2.5 concentrations for reduction efficiency.

The indoor environment of buildings is of fundamental importance for the health of people and other living organisms residing in them. From this perspective, key factors include indoor temperature, relative humidity and the concentration of CO₂ or other pollutants. These healthy indoor conditions are typically maintained through functional heating and ventilation systems. However, in the case of indoor humidity, increasing moisture levels when they are low can be relatively challenging. There are more energy-efficient solutions that can be combined with ventilation systems. These include, for example, placing plants and green walls in the interior, which have a significant impact not only on microclimatic and acoustic conditions of the interior, but also on the overall psychological well-being of occupants. Green elements contribute to the effective regulation of CO₂ and certain other harmful substances within the indoor environment. Another possible solution involves the use of sorption-active materials in the form of cladding panels—elements capable of functioning as indoor regulators, i.e., absorbing moisture and releasing it back into the indoor environment when necessary. This study investigates the moisture behavior of natural composites based on montmorillonite clay and straw fibers, as well as their possible integration with green elements to create healthy indoor conditions for their inhabitants. The developed clay composite can be classified as water and steam absorption class WSIII according to DIN 18948—the moisture buffering capacity value was 152.73 g/m² after 12 h. Based on the research results, it can be stated that these composites could serve as interior cladding elements in synergy with green elements (Chlorophytum comosum, Epipremnum aureum), ideally regulating the indoor microclimatic conditions, especially as an effective solution for short-term humidity changes. The maximum difference in relative humidity between the reference testing chamber (without green elements and clay plates) and the chamber containing plant Chlorophytum comosum and three clay composite plates was 23.04%.

Mineral substrates for indoor horticulture systems critically determine plant water availability and irrigation demand. However, integrative assessments linking pore structure, water retention, and evaporation dynamics of commonly used mineral growing media remain scarce. A total of nine distinct mineral substrates were investigated: expanded clay, expanded slate, pumice, perlite, zeolite, vermiculite, lava granules, brick chips, and clay granules. To assess the impact of granulometry, pumice was tested in three different grain sizes (1–3 mm, 4–7 mm, 7–14 mm), resulting in a total of 11 experimental samples. Samples were characterized using scanning electron microscopy (SEM), suction experiments, and evaporation tests at 30%, 50%, and 70% relative humidity (RH) at 23 °C. Bulk density ranged from 0.99 g·cm⁻³ (zeolite, brick chips), while volumetric water content varied from 11.0 vol.% (expanded clay) to 46.6 vol.% (vermiculite). Plant-available water content (AWC) ranged from 2.7 vol.% (expanded clay) to 30.9 vol.% (clay granules). These results demonstrate that pore interconnectivity, rather than total porosity, is the decisive driver of hydraulic performance. Finer pumice fractions increased water retention by ~16% compared to coarser fractions. All substrates exhibited a two-phase evaporation profile, with initial rates ranging from 1.9 to 5.6 g·h⁻¹ at 30% RH. Clay granules showed the most temporally stable evaporation, with only a 37% rate reduction over 48 h, compared to 66% for perlite. While conducted under controlled laboratory conditions, these findings provide a quantitative basis for targeted substrate selection and blending to optimize root-zone hydration, irrigation efficiency, and hygrothermal performance in permanent indoor horticulture systems.