An interesting article from the University of Oregon, titled “Identification of SARS-CoV-2 RNA in Healthcare Heating, Ventilation, and Air Conditioning Units“, has been published. The study involved the swabbing of different locations across various air handlers in a hospital to examine for the novel coronavirus Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2).
Of concern was the fact that the virologists recovered the virus on around 25 percent of swabs. Of even greater concern was then recovery of the virus from both supply and return air. Hospital room ventilation systems – Heating Ventilation and Air Conditioning (HVAC) – typically recirculate air and pass it through a filter. These filters are of variable design; some can filter out larger (macro-sized particles), others filter bacteria, but not all can capture viral particles (or viral particles in sufficient numbers).
In the paper the authors state:
“This study demonstrates SARS-CoV-2 RNA contamination throughout several AHUs path of flow, including return air, two filtration stages, and supply air, for multiple floors of the hospital and serves as the first evidence of the potential for SARS-CoV-2 RNA (and possibly virus), irrespective of viability, to enter into and travel throughout HVAC systems.”
In essence, the virus entered MERV-15 filters and moved into supply air ducts.
The researchers sampled nine different air handling systems. They recovered viral RNA. The recovery of viral material is not necessarily an indicator of viral infectivity (the researchers did not determine this). However, it draws attention to a vulnerability in the healthcare setting. Modifications can be made to HVAC systems, such as the use of ultraviolet light which can inactivate viral particles. In addition, albeit an expensive solution, higher grade filters with smaller porosity can be fitted. The findings also point to the need to consider building air system design.
