Facing current pandemia, some manufacturers are currently actively promoting some new devices or processes said as « anti‐Covid‐19 ». INRS (French National Research and Security Institute) warns companies and employees against some of these innovations that not only do not reduce the virus transmission risk but can creates new ones.
Interests of the biocidal coatings, efficiency of the air purifiers, risks linked to UV or ozone disinfection... In the fight against Covid‐19, many companies ask INRS experts about efficiency and safety of these solutions.
What is the interest of biocidal coatings in the fight against Covid‐19 ?
Some coating products with biocidal function are currently proposed in the form of membranes, adhesive taps or varnish to be applied on surfaces. The main selling argument is the long lasting disinfecting action toward many different microorganisms, including coronavirus. Such an action supposes, as a minimum, that the biocidal contained in the coating has an effect on the targeted microorganism (SARS‐CoV‐2) and that this effect is fast. The surface to be disinfected must also be beforehand cleaned before being perfectly covered by that coating.
It may be recalled that disinfection is considered only for surfaces presenting a high risk of contamination, meaning approached and touched by many persons. Quickly covered with skin flakes, greases and other dirts, these surfaces require thus a very frequent cleaning in order that the biocidal coating still have an action. This amounts to make cleaning operations that are, in any way, recommended in the current sanitary context, even without any biocidal coating. Indeed, tensio-actives present in the classic cleaning products destroy the coronaviruses lipidic envelope and already allow to inactivate it.
In view of the uncertainties concerning the efficiency of these biocidal coatings and the necessary conditions so that it can have an effect like their frequently cleaning, these products must not be recommended as a way to fight against virus transmission.
What are indoor air purifiers ?
These devices suck the air of a working area and throw it back in the same area after having treated it with different methods. Based on HEPA filtration, it can reduce the concentration of viruses likely to be present in the air but can not, in any way, replace outdoor air supplies defined by the Labor Code. Functioning in continuous mode or in sequential mode, these devices must thus only be used as a complement to ventilation systems (and to keep acceptable working conditions, namely in winter
Only devices equipped with HEPA filters minimal class H13 according to norm EN 1822‐1 and installed in such a perfectly hermetic way allow to stop efficiently aerosols that can spread the virus, thank to a regular maintenance according to manufacturer’s recommendations. It is also necessary to ensure that these indoor air purifiers are adapted to the area volumes in whom it is installed and that it do not generate too high speeds to limit the droplets dispersion.
It is highly not recommended to choose devices using an air physico‐chemical treatment (catalyse, phtocatalyse, plasma, ozonation, active carbons...). Not only its efficiency toward viruses is not proven but also after a pollutants degradation sometimes incomplete, it can impact negatively the indoor air quality by the formation of compounds potentially harmful for human health including CMR chemical agents.
What are the precautions to take in case of UV disinfection ?
UV‐C ray lamps said « germicidal » are widely used in healthcare field, in laboratories but also for the air and water treatment as well as in food industry. Concerning the disinfection of premises, that system requires that all surfaces are exposed to a direct ray (no effect behind a partition or below a furniture as an example) and cleaned beforehand (virus can be protected from the rays by dirts). Caution, some disinfecting chemicals like chlorine based ones can be decomposed of secondary products likely novice for human health under UV action. For persons exposed to UV‐C rays, risks for human health can be substantial : to the skin with « sunburns » ranging from simple erythema to more serious lesions as well as to the eyes level with cornea inflammation and conjunctives. Some highly energetic lamps issue a ray in the distant UV domain leading to ozone production in non negligible proportions.
Labor Code sets occupational exposure limit values in order to protect employees. As an example, a few minutes exposure of the skin or the eyes at 1,5m from a standard lamp would lead to a passing of the daily occupational exposure limit value. As a consequence, buyer must make sure of the CE conformity of the device issuing UV‐C that must never function in presence of employees and always be operated by experienced personals.
Is surfaces disinfection with ozone without any risk ?
As for the use of gaseous ozone as a biocidal for surfaces disinfection, if several studies present good results on several bacteria, moulds and yeasts, bibliographic research never found any study on « enveloped » viruses like SARS‐CoV‐2.
It may be recalled that ozone is an irritant gas for the skin and especially for eyes and mucous membranes. According to the inhaled dose, some troubles can appear, going from a light irritation of mucous membranes and a buccal dryness to pulmonary lesions. It can also go along with neurological ravages (headaches, tiredness, coordination troubles...). In addition, even if ozone is not flammable, it can also lead to combustion of flammable materials and be at the origin of explosions, under certain conditions.
Currently, in France, some companies suggest the use of ozone generators for deodorization, even for premises disinfection. According to the documentation provided by these companies, offered equipment generate ozone concentrations until more than 100 times higher than the daily occupational exposure limit values. In these conditions, treatment protocol of premises with gaseous ozone must guarantee the absence of persons as well as the absence of gas leaks toward nearby premises. In addition, an air purification phase, with ozone residual concentration monitoring, must be organized after the treatment before giving the authorization to enter in the premises.
Regarding risks entailed by the use of gaseous ozone and uncertainties concerning its efficiency toward SARS‐CoV‐2, the application of chemical risks prevention process impose to try to substitute that method by another less dangerous process, while insuring that it fulfills initial objective to eliminate the virus.