What question did this study set out to answer?

This research aims to explore the levels of microbial contamination in windowless exhibition spaces reliant on centralized air conditioning.

February 8, 2026Open Access

Microbiological Air Quality in Windowless Exhibition Spaces with Centralized Air-Conditioning and Air Recirculation—Pilot Study

Puntos clave

This research aims to explore the levels of microbial contamination in windowless exhibition spaces reliant on centralized air conditioning.
Assessed microbiological contamination using Koch’s passive sedimentation method over a 24-hour period.
Monitored CO2 levels to evaluate ventilation demand and occupancy effects.
Compared contamination levels across two different air-handling units and selected exhibition rooms.
AHU I showed higher levels of Staphylococcus sp. and fungi, while AHU III had elevated fungal peaks.
Psychrophilic bacteria ranged from 140 to 230 CFU·m−3, mesophilic bacteria from 230 to 320 CFU·m−3, and fungi up to 740 CFU·m−3.
Several CFU values exceeded recommended thresholds, indicating potential health risks and the need for improved ventilation and filtration.

Resumen

Microbiological contamination in public buildings is closely linked to human presence, such as airborne bacteria, fungi, and particulate matter, which strongly influence indoor air quality (IAQ). This study examined the distribution of microorganisms in a museum building in relation to time of day, air-handling unit (AHU) type, and ventilation operating mode. Exhibition rooms without natural light relied entirely on a central heating, ventilation and air conditioning (HVAC) system. Microbiological contamination was assessed using Koch’s passive sedimentation method over a 24 h cycle for two AHUs (I and III) and selected rooms, while CO2 levels were monitored as indicators of occupancy and ventilation demand in line with EN 16798-1:2019 and ASHRAE 62.1-2022. Although the demand-controlled ventilation system increased the outdoor air fraction from 40% to 70–100% during peak visitor density, localized increases in microbial contamination occurred. AHU I showed higher loads of Staphylococcus sp. and fungi, while AHU III exhibited pronounced fungal peaks influenced by elevated humidity from an open water reservoir. Psychrophilic bacteria reached 140–230 CFU·m−3, mesophilic bacteria 230–320 CFU·m−3, and fungi up to 740 CFU·m−3. Most CFU values remained below commonly referenced upper limits (<1000 CFU·m−3), but several peaks exceeded lower recommended thresholds, indicating a need for improvements. Enhanced filtration, humidity control, increased airflow during high occupancy, and reducing moisture sources in AHUs may mitigate microbial growth and improve IAQ in public buildings.

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