Experimental evaluation of positive and negative air ions disinfection efficacy under different ventilation duct conditions

摘要

This study investigated the effectiveness of different polarities of ionizers in inactivating bioaerosols in a duct flow condition. Three bacteria species-Escherichia coli (E. coli), Salmonella typhimurium (S. typhimurium), and Staphylococcus epidermidis (S. epidermidis)-were aerosolized into the duct under three airstream velocities, ranging from 3.0 to 6.5 m/s. The positive ionizer showed better disinfection performance than the negative ionizer by 29%-41%. Our results showed an inverse correlation between air velocity and the disinfection efficiencies. As the velocity was increased from 3.0 to 6.5 m/s, the corresponding disinfection efficiencies of positive ionizer decreased from 88.5% to 44.0%, 49.0% to 38.7%, and 35.1% to 19.8% for E. coli, S. typhimurium, and S. epidermidis, respectively. For the negative ionizer, the corresponding disinfection efficiencies decreased from 62.9% to 35.4%, 54.2% to 30.0%, and 42.9% to 30.2% for E. coli, S. typhimurium, and S. epidermidis, respectively. The positive ionizer was further tested at three relative humidity levels (50%, 70%, and 90%) and three temperature (17.5 degrees C, 21.0 degrees C, and 25.0 degrees C) levels. From 50% to 90% relative humidity, the disinfection efficiencies decreased from 46.0% to 23.6%, 35.2% to 22.5%, and 24.8% to 20.7%, for E. coli, S. typhimurium, and S. epidermidis, respectively. At the same time, the efficacy of the ionizer increased as temperature decreased. Therefore, from a temperature of 17.5 degrees C to 25.0 degrees C, our results show that the disinfection efficiencies decreased from 56.0% to 32%, 38.8% to 22.6%, and 24.8% to 21.5%, for E. coli, S. typhimurium, and S. epidermidis, respectively. The ozone emission rates of both ionizers were measured and found to be very small.