Air filtration: Do we have sufficient evidence to implement these air filtration equipment programs??

 https://www.ashrae.org/file%20library/technical%20resources/covid-19/core-recommendations-for-reducing-airborne-infectious-aerosol-exposure.pdf?fbclid=IwAR2QOQjdHtDP8Pgmse52ouEjIfLCt6MbypIZqH9UF7l6dUeLtyUWuRx8KGM

https://smartairfilters.com/en/blog/hepa-filter-release-dirty-particles-into-air/ 

The issue of air treatment in establishments open to the public is indeed closely linked to the risk of airborne propagation of micro-organisms and other pathogens. This question is not new since it has arisen and still arises in healthcare establishments, whether in the operating theatre or hospital departments and emergency rooms. The pandemic has led to reconsidering this issue of air treatment in addition to personal protection such as masks and social distancing.

1/ it is above all an economic question, the investments and operating costs are high, in particular for equipment with filtration or a virucidal or bactericidal device by UV, for example. Existing systems are rarely adaptable because the power of the air propulsion engines is insufficient. Operation assumes electrical consumption that has not been modelled for all of these buildings.

2/ The potential advantages are significant because they concern all pathologies linked to an agent transported by the air. These agents are numerous, infectious, allergic and toxic and their consequences on human health are fairly well documented. However, it is necessary to differentiate between short-term risks such as an influenza epidemic or a particularly important pollen episode and long-term risks such as particulate pollution... Large health databases make it possible to approach the economic benefit of such facilities.

3/ Solid evidence remains to be established. The number of randomized trials in this area is very limited. Public aid programs do not prejudge this evidence because the equipment is very varied in its effectiveness and cost. For example, portable devices for apartments can be efficient and inexpensive but what about schools (https://onlinelibrary.wiley.com/doi/10.1111/ina.13029)? Searching for randomized controlled trials with the title: "air filtration efficacy in respiratory infection" finds only 5 articles... This is why it is so important to obtain solid evidence before deciding on such expenditures. Public funds would be better used to improve this evidence, especially in real life, whether it concerns filtration methods in general but also devices in particular.

https://jamanetwork.com/journals/jama/fullarticle/2793289?widget=personalizedcontent&previousarticle=2793733