This study aimed to assess the prevalence of airborne microorganisms within the packaging areas of (semi) liquid food product facilities, considering the impact of outdoor microbiological air, seasonal fluctuations, rural-urban differences and environmental parameters such as temperature and relative humidity. Additionally, the effectiveness of both natural ventilation and air handling units were evaluated against total viable and non-viable particulate matter.Air samples were collected from the packaging areas of fourteen diverse (semi) liquid food producers and the outdoor environment in Flanders, Belgium, over the course of four separate days from January to September 2022. Airborne microorganisms, including total mesophilic plate count (TMPC) and yeast and mould (Y&M) count, were sampled using impaction and settle plate methods on Plate Count Agar and Rose Bengal Chloramphenicol agar, respectively. Simultaneously, a laser particle counter was used to collect and categorise particles into six size-based channels, while environmental parameters were monitored using a hygrometer.The study revealed a wide range of concentrations of airborne microorganisms across various companies (indoor TMPC ranging from 1.35 ± 0.65 log cfu/m3 to 3.42 ± 0.16 log cfu/m3 and Y&M count ranging from 1.22 ± 0.65 log cfu/m3 to 3.10 ± 0.08 log cfu/m3), irrespective of outdoor air quality. Neither relative humidity nor temperature exhibited any influence on TMPC and Y&M count. Companies equipped with high-efficiency filter air handling unit showed decreased concentrations of airborne microorganisms, although this trend did not align with their total particle counts. Moreover, no correlation was observed between total particle count and either TMPC or Y&M count. Additionally, impaction and sedimentation methods demonstrated a strong correlation.In conclusion, the diversity in airborne microorganism concentrations within food packaging areas is influenced by multiple factors, with air handling unit filters playing a pivotal role. High-efficiency filters were found to reduce microorganism levels, but their impact on total particle counts was less pronounced.