An Exploratory Comparison of Indoor Air Quality and Culturable Airborne Microbial Concentrations Among Hospital Waiting Areas With Different Ventilation Conditions in Northern Thailand

Few studies have simultaneously characterized physical, chemical, and culturable biological indoor air quality (IAQ) in hospital waiting areas, particularly in tropical healthcare settings. This exploratory observational environmental monitoring study assessed PM _2.5 , PM ₁₀ , CO ₂ , CO, thermal environmental parameters, and culturable airborne bacterial and fungal concentrations in five hospital waiting areas with different ventilation conditions in Northern Thailand. Measurements were conducted over nine sampling days and summarized at the room-day level to account for repeated spatial measurements. Significant overall differences among waiting areas were observed for PM ₁₀ (p = 0.0012), temperature (p = 0.0006), culturable bacteria (p = 0.0050), and culturable fungi (p = 0.0007), whereas PM _2.5 , relative humidity, CO, and CO ₂ did not differ significantly at p < 0.01. No pairwise comparison remained significant after Holm adjustment. Descriptively, Room E, the only mechanically ventilated waiting area, generally showed lower PM ₁₀ and culturable bioaerosol concentrations than several naturally ventilated waiting areas; however, these differences cannot be attributed exclusively to ventilation condition because mechanical ventilation was represented by only one room. Neither mixed-effects models (bacteria: p = 0.062; fungi: p = 0.153) nor room/day fixed-effects sensitivity analyses (bacteria: p = 0.542; fungi: p = 0.447) showed significant associations between PM ₁₀ and culturable bacterial or fungal concentrations. These findings demonstrate substantial room-specific heterogeneity in IAQ and provide a site-specific baseline for future multi-site studies and targeted ventilation, filtration, and IAQ management strategies in hospital waiting areas.