TABLE 1.

a comparison between the most common methods of air filtration and purification that are used to fight bacteria, fungi and virus spread.

	HEPA filters		UV radiation	Ionization
Mode of action and properties	It functions by the combination of three aspects. First, outer filters that work like sieves to stop the larger particles of dirt		Air disinfection using 254 nm UV-C is an effective tool for inactivating viral erosols. Air microbes, genetic material and protein absorption the UV light resulting in severe cellular damage to the organism Walker and Ko (2007)	It can prevent transmission of airborne viral infections. The ionization device consists of a small portable ionizer, where a sampling cup of positive charge is attached to the ionizer attracting negative particles from the air
	A concertina filter–a mat of very dense fibers–forms the middle layer which traps smaller particles. These are designed to remove 90% of particles from the air. The inner part catch particles as they pass through in the moving air		Air cleaners alone or combined with upper-room air Ultraviolet germicidal irradiation (UVGI) can purify the air by removing bioaerosols at significant rates in high-exposure environments such as hospitals, correction facilities Kujundzic et al. (2006)	Higher numbers of viral particles detected on the active ionizer compared to the inactive ionizer led to the conclusion that this technique can efficiently capture and collect viral particles from the air Hagbom et al. (2015)
	Different grades of HEPA filters differ in their ‘efficiency ratings’. The most used HEPA filter is the H14 filter, which is designed to eliminate 99.997% of particles from the air Sandle (2013)
	The performance of the HEPA filter system depends on its setting and position. Nevertheless, the use of a mobile HEPA filter system seems a good alternative to use when no ventilation options are available Bluyssen et al. (2021)
Efficiency	Commercial HEPA filters (99.95%) retain more than 9.996% of actinophage particles Roelants et al. (1968), Dee et al. (2006), Christopherson et al. (2020)	Titanium dioxide (TiO2)-coated HEPA filters were shown to be able to remove 60–80% of airborne spore-forming bacteria and fungi Chuaybamroong et al. (2010)	Exposing viral particles to UV-C for 1 s is lethal and possesses the potential to inactivate the viral particles Sabino et al. (2020)	Air ionizers are capable of purifying the air of fine and ultra-fine particles with high efficiency Grabarczyk (2001), Uk Lee et al. (2004), Shiue et al. (2011), Pushpawela et al. (2017)