## 4 Discussion  
This paper had the objective of reviewing the existing literature, concerning the biocidal agents that are used in order to ensure healthcare settings surfaces disinfection against SARS-CoV-2. The transmission of severe acute respiratory syndrome coronaviruses occurs not only thorough direct physical contact with infected subjects or large-droplet spread but also via contact with environmental contaminated surfaces (indirect transmission) [41; 42]. Viruses are pathogens commonly present in hospitals and many of them, including human coronavirus, can survive for hours on hands but also on environmental surfaces [43; 44], creating an outbreak of nosocomial transmission. The experiment performed by [PERSON] et al. [45] in which the production of aerosol was simulated by a three-jet Collision nebulizer and fed into a Goldberg drum, recorded that SARS-CoV-2 would be able to survive for 72 h on plastic and stainless steel, 24 h on cardboard, and 4 h on copper. The virus survived approximately 2.7 h in the simulated aerosol. Similar data were obtained during the same experiment conducted by [PERSON] et al. [21]. Therefore, healthcare settings surfaces decontamination results to be crucial in the prevention of SARS-CoV-2 spread [43]. All the studies proposed alcohol based disinfection agents against SARS-CoV [27; 32; 33; 37; 38]. Alcohol-based products inactivate virus particle by disrupting the structure of proteins on the surface of SARS-CoV-2, thorough the mechanism called protein denaturation: alcohol displaces the hydrogen bonds between amino acids holding the viral proteins in shape, and as a consequence, proteins lose their structure and function, thereby inactivating the virus. The research conducted by [PERSON] et al. [46] tested the efficacy of 62%, 70%, and 71% ethanol (undiluted), 0.55% orthophthalaldehyde, sodium hypochlorite, and phenol (diluted in hard water) on coronaviruses contaminated healthcare settings hard surfaces, showing that only ethanol has the capacity to reduce the virus infectivity by \(>\)3 log\({}_{10}\) after one minute of exposure. Another study [47] proved the efficacy of different biocidal agents against human coronavirus 229E, considering as virucidal effectiveness criterion a reduction of viral activity of \(\geq\)3 log\({}_{10}\): ethanol 70% alone or combined with chlorhexidine gluconate 0.008% and cetrimide 0.08%, phenol 5% plus sodium lauryl sulphate 0.06%, and alkaline glutaraldehyde 2% were able to guarantee an important activity against the virus, as opposed to sodium hypochlorite 0.01%, quaternary ammonium 0.04%, and triple phenolic 0.06%, whose action was not sufficient to inactivate the pathogen. Several included articles inserted the use of chlorine-containing disinfectants in their cleaning protocols [29; 30; 32; 38]. The exact mechanism by which chlorine kills the viruses is still unclear. The virus inactivation may result from inhibition of protein synthesis, loss of intracellular contents, reduction of nutrients or oxygen uptake, oxidation of amino acids, etc. [PERSON] et al. [48] reviewed the literature in order to find preventive measures to limit the spread of SARS-CoV. In addition to ethyl alcohol 70%, this review proposed the use of chlorine compounds solutions, after an accurate pre-cleaning, to obtain floor and large-surface decontamination. Phenolic detergent disinfectants could substitute chlorine when corrosion, bleaching, or gas production are to be avoided. Another effective cleaning method is represented by ultraviolet light (UV-C), which reduces the viral contamination in healthcare settings thanks to its action on surfaces and air column [36]. UV-C (with wavelengths equal to 207-222) is able to damage the proteins on the surface of the virus, preventing them from attaching human cells. UV-C works through the use of lamps producing high-intensity ultraviolet C light, which is an electromagnetic radiation form [49]. The utility of this technology has been proven by [PERSON] et al.