The sanitization and disinfection of public and private environments and means of transport are among the most sought-after methods of containment of thesanitary emergency resulting from the spread of COVID-19. The scenario of the most used technologies sees the primacy of those based on ozonation, ionization, photocatalysis, filtering which prove to be fundamental for reducing the transmission of the virus in an effective and persistent way.
OZONE AND SANITIZATION OF ENVIRONMENTS
As is known, ozone is a hyper-oxidizing gas capable of effectively eliminating microorganisms such as bacteria, viruses, mould, spores, fungi, mites, especially when used to saturate limited environments. It is a gas that cannot be stored or transported due to its high reactivity, but is generated in situ from air, oxygen or water.
The most common – and most advantageous – ozone production method iscorona effect. This process involves a flow of dry air – or, more simply, oxygen – being passed through a high voltage electrical discharge which breaks the stable oxygen molecule, giving rise to the process of ozone formation. Another production process - albeit less advantageous than the previous one - is foreseen ultraviolet lamps with emission band concentrated on 185 nm. The limits of this system are greater electrical consumption, lower ozone productivity and, lastly, the brevity of the lamps' operational life, with the elements connected to the resulting pollution. Finally, a third possible process is that aimed at the production of ozone to be used in aqueous solution which starts fromwater electrolysis. Once produced, according to the most convenient process, ozone appears as a broad-spectrum germicide, thanks to its ability to attack and destroy the cell membrane, resulting in lysis.
In terms of environmental sanitation, the use of ozone develops following treatment cycles precise, composed of various phases, as reported in the "ISS COVID-19 Report n. 56/2020” produced by ISS and INAIL. The stages that mark a treatment cycle start from the conditioning phase, in which ozone begins to be supplied to the room to be treated, saturating the environment with the concentration suitable for the reference objective. Thus follows the actual action phase of the ozone which, with doors and windows closed for the necessary time, guarantees the sanitizing action. The cycle ends with the phase of elimination of residual ozone; a phase of great importance for the safety of the occupants of the cycle site. When the generator is turned off, the ozone concentration gradually decreases due to the spontaneous reconversion of ozone into oxygen.
ADVANTAGES IN USING OZONE
The use of ozone, and therefore of ozonizers, has numerous benefits. Firstly, the gaseous nature of this disinfection system means that even the most complex surfaces and less accessible points of an environment can be reached. In addition to this high degree of effectiveness, the costs are very low for each sterilization cycle - there is no need for particular manpower or ordinary maintenance - and the action times are extremely short.
Furthermore, do not forget that the use of any chemical product is not necessary in its production process, but only air and electricity. Carried out according to correct methods, the process of eliminating viruses, bacteria, mold and yeasts with ozone does not produce organic or inorganic residues: the ozone, obtained with appropriate technological systems, once its cycle is finished, transforms back into oxygen without leave traces unlike other chemical products. In these terms, this technology reduces emissions of harmful substances for the environment, presenting itself as a system that combines efficiency, economy and attention to the environment.
OZONIATORS AND SAFETY, BETWEEN PROCEDURES AND TECHNOLOGIES
The ozonizers available on the market can be divided based on operating mode and to production capacity, which depends on the use - more or less professional - for which they are intended. Those with greater production capacity are intended for large environments and allow the adoption of customized protocols; they are also characterized by technologies for cooling the cell, to limit the production of heat. Differently, ozonizers with lower production capacity - suitable for small environments - are equipped with predefined programs that cannot be modified and tend to be enriched by an ozone reconversion device at the end of supply.
Variable of fundamental importance, the ozone precursor in the production process it can be - and this is what occurs in most cases - ambient air or oxygen of purity > 95% deriving from cylinders or portable concentrators. As defined by the ISS, this is the range that outlines the possible production of harmful substances or, on the contrary, the absence of toxic waste.
Although the use of oxygen present in the ambient air is simple and economical, it can lead to the production of harmful substances, mainly nitrogen products, depending on the type of ozone cell and its operating methods. “The use of closed cell generators, rather than generators that use surface plate corona discharge, offers fundamental quality and durability advantages – we read in the COVID-19 Report n. 56/2020 – and the air that feeds the cell must be purified and dehydrated. In fact, it is necessary for the generators to be equipped with a specific filtration system for the ambient air source in order to retain any possible contaminants present and avoid or limit the generation of reaction by-products harmful to the human organism".
With the use of an ozone cell powered by purity oxygen > 95% however, there is the certainty of not generating secondary pollutants, but also the possibility of achieving higher yields and concentrations of ozone in the delivered flow, even though the equipment is more complex and expensive. In either case, the user manual provided by the manufacturer must highlight the risks due to the production of harmful substances or the generation of heat/fires, as well as the prevention strategies.
Of course the equipment, as electrical devices, must also pass the electrical safety testing, carried out according to a harmonized standard of the LVD Directive 2014/35/EU, as well as the electromagnetic compatibility.
OZONE AND THE REGULATORY ASPECT
Already validated in 2001 by the US FDA (Food and Drug Administration) as safe and effective in food processing, ozone was introduced in Europe in 2003 for disinfection and sterilization during manufacturing processeswater bottling. On that occasion, the possibility of separating the components of natural mineral waters and spring waters through "treatment with ozone-enriched air", as reported in the amended Directive 80/777/EEC, was defined. In Italy, however, the Ministry of Health has recognized - with the protocol of 31 July 1996 n°24482 - the use of ozone in the treatment of air and water, as a natural protection for the sterilization of environments contaminated by bacteria, viruses, spores, molds and mites.
For the CE certification of the products all the tests indicated in suitable harmonized standards must be carried out for the electrical safety check And electromagnetic compatibility. The manufacturer or importer can carry them out independently if they are equipped with the necessary equipment and skills, or entrust them to specialized external laboratories.
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