Microbial analysis of a built environment with disinfection based balanced ventilation system

Ensuring a healthy indoor environment, especially in urban areas is crucial. The use of outdoor air-assisted balanced heat recovery ventilation (B-HRV) systems in air-conditioned buildings has gained traction to minimize indoor infectious bio effluent CO₂. However, excess outdoor air intake raises concerns about microbial infiltration. This study integrated two modes—ultraviolet germicidal irradiation (UVGI) and chemical spraying (CS)—into the B-HRV system to mitigate microbial concentrations. Operating at optimal Air Changes per Hour (ACH) aligned with ASHRAE 62.1 standards, the system was tested and evaluated for pre- and post-sampling of indoor, outdoor, and susceptible surfaces. The B-HRV’s incoming air section exhibited higher surface microbial contamination due to dust and humidity. UVGI reduced indoor air total bacterial count (TBC) by 91% and total fungal count (TFC) by 49.7%. CS mode achieved over 97.5% reduction in both TBC and TFC, outperforming UVGI in microbial removal. Statistical analysis (p < 0.0001) showed a significant correlation between pre- and post-disinfection microbial reduction counts for both methods. Conclusively, deploying both UVGI and CS modes is recommended to maintain Indoor Air Quality (IAQ) and ensure a clean environment in air-conditioned buildings.