Our previous studies demonstrated that precoating of filter fibers with biologically active tea tree oil (TTO) enhances physical collection efficiency of conventional heating, ventilation, and air conditioning (HVAC) filters, and provides cost effective and rapid inactivation of captured bacterial and fungal particles on the filter surface. The main aim of this study was to investigate the antiviral activity of two natural disinfectants, i.e., TTO and eucalyptus oil (EUO), against the influenza virus captured onto the filter surface. It was found that both tested oils possess strong antiviral properties when used as fiber coating materials, capable of inactivating captured microorganisms within 5–10 min of contact on the fiber surface. The antiviral activity of TTO was also successfully challenged in aerosol form by mixing viable airborne viral particles with oil droplets in the rotational aerosol chamber. The results look very promising for further development of virus inactivating procedures and technologies for air quality applications. Copyright 2012 American Association for Aerosol Research

Abstract Continuous emission of unipolar ions has been shown to improve the performance of respirators and stationary filters challenged with non-biological particles. In this study, we investigated the ion-induced enhancement effect while challenging a low-efficiency heating, ventilation and air-conditioning (HVAC) filter with viable bacterial cells, bacterial and fungal spores, and viruses. The aerosol concentration was measured in real time. Samples were also collected with a bioaerosol sampler for viable microbial analysis. The removal efficiency of the filter was determined, respectively, with and without an ion emitter. The ionization was found to significantly enhance the filter efficiency in removing viable biological particles from the airflow. For example, when challenged with viable bacteria, the filter efficiency increased as much as four- to fivefold. For viable fungal spores, the ion-induced enhancement improved the efficiency by a factor of ∼2. When testing with virus-carrying liquid droplets, the original removal efficiency provided by the filter was rather low: 9.09 ± 4.84%. While the ion emission increased collection about fourfold, the efficiency did not reach 75–100% observed with bacteria and fungi. These findings, together with our previously published results for non-biological particles, demonstrate the feasibility of a new approach for reducing aerosol particles in HVAC systems used for indoor air quality control.

A new personal bioaerosol sampler has recently been developed and evaluated for sampling of viable airborne bacteria and fungi under controlled laboratory conditions and in the field. The operational principle of the device is based on the passage of air through porous medium immersed in liquid. This process leads to the formation of bubbles within the filter as the carrier gas passes through and thus provides effective mechanisms for aerosol removal. As demonstrated in previous studies, the culturability of sampled bacterium and fungi remained high for the entire 8-h sampling period. The present study is the first step of the evaluation of the new sampler for monitoring of viable airborne viruses. It focuses on the investigation of the inactivation rate of viruses in the bubbling process during 4 h of continuous operation. Four microbes were used in this study, influenza, measles, mumps, and vaccinia viruses. It was found that the use of distilled water as the collection fluid was associated with a relatively high decay rate. A significant improvement was achieved by utilizing virus maintenance fluid prepared by using Hank's solution with appropriate additives. The survival rates of the influenza, measles, and mumps viruses were increased by 1.4 log, 0.83 log, and 0.82 log, respectively, after the first hour of operation compared to bubbling through the sterile water. The same trend was observed throughout the entire 4-h experiment. There was no significant difference observed only for the robust vaccinia virus.