KillVir – UV-C Air Disinfection

This virus is so new that more of this data has not yet been published. However, we found the first results of work in this field from Italy, the USA and the Netherlands. A summary of their results is given in a clear table. Values for influenza virus and tuberculosis bacteria are given for comparison:

H90 (H99) – the dose of UV-C energy required for 90% (99%) inactivation of the
pathogen

However, some well-known similar viruses from the SARS family need values up to 2.6 times higher than the SARS-CoV-2 virus. More detailed tables for other pathogenic microorganisms can be found in the Aeroterm KillVir Datasheet or web page.

First of all, it is necessary to determine which microorganisms we want to eliminate and with what percentage of efficiency (for table data, see eg the Aeroterm KillVir Datasheet or web page). It is necessary to take into account the nature of the room (office, waiting room, dental office…). Microbiological pollution is brought by people and animals – it is therefore necessary to consider their number, density, number of arrivals. Accordingly, determine by which reserve to increase the selected required dose of UV-C energy. Indeed, the minimum reserve should be 20% to reduce the efficiency by dusting UV emitters and 10% to reduce the efficiency of UV-C emitters at the end of their service life. The device is then selected according to the minimum amount of UV-C energy thus determined and increased. The disinfection device must provide this necessary increased amount of UV-C energy, – ie. a dose equal to or greater than the indicated dose for the pathogen per pass of air through the device. Every manufacturer or retailer must state these essential parameters. Of course, there are also a number of products on the market whose effect is undefined, and this absence is being replaced by massive advertising and strong expression.

Example:

We decided to eliminate not only the SARS-CoV-2 virus, but also, with 99% efficiency, the influenza virus, which will attack us in various mutations even after the pandemic subsides. Influenza viruses are more resistant than SARS-CoV-2 and a dose of UV-C energy H99 = 72J/m2 is required for their 99% elimination. If we consider a reserve of 50% (30%), we will require the disinfection device to provide a dose of UV-C energy E = 72×1.5 = 108J/m2 (94J/m2). This corresponds to the Aeroterm KillVir HB475 device with a dose of H = 127J/m2 (suitable for large rooms) or the Aeroterm KillVir LS430 type, which provides a UV-C energy dose of H = 115J/m2 (suitable for smaller rooms).

A very important function of the disinfection device is to be able to move the air in the room so that the desired air circulation occurs throughout the room and not only in the immediate vicinity of the device.

For example, the air in a smaller room 6x4x2.6m, whose volume is 62.4m3, weighs about 75kg. These facts require that the device be equipped with a powerful fan unit. The optimal condition is that the volume of the room is pumped by the device within 1 hour, the worst within 2 hours. The sooner, the faster the disinfection effect starts. This corresponds to the fact that for a given device, the optimal room size is up to the value of the stated actual air flow through the device (some manufacturers state the nominal fan flow, but the actual flow is significantly lower). However, it must always be the case that the device must emit a sufficient dose of UV-C energy to inactivate the pathogen. For larger rooms and complicated rooms, more devices can be purchased. For rooms with high risk and frequent door opening frequency, it is necessary to choose a device with the highest possible air flow.

Example:

Aeroterm KillVir LS475 device with UV-C energy dose H = 127J/m2 and air flow through the device Qv = 187m3/h or eg Aeroterm KillVir LS430, with UV-C energy dose H = 115J / m2 and flow Qv = 96m3/h can be used for 99% elimination of influenza virus. These devices provide a similar dose of UV-C energy, but differ in the value of the air flow through the device. Type HB475 is therefore optimal to use in rooms up to 187m3 (11x6x3m), type LS430 in rooms up to 96m3 (7x5x2.7m).

The KillVir UV-C disinfection device has the unique advantage that it can work even in the presence of people and thus continuously reduce the amount of pathogens in the room. The device can be operated continuously, 24 hours a day for 18,000 operating hours (approx. 2 years). Then the UV-C tubes need to be replaced. If you need to move to different rooms and try to keep it in the room in the shortest possible time, it is necessary to remember that the air in the room has to be put in motion and circulate for a while. We recommend a minimum of 2 hours for a room that has a volume less than or equal to the flow rate of the particular model. In larger rooms, up to twice that time. In general, however, it is best to have the disinfection device switched on while people are in the room and ideally for at least an hour afterwards in order to continuously disinfect the air. Otherwise, the microbiological load would continue to increase. This should be supplemented by disinfecting the surfaces (by wiping the surfaces with a disinfectant solution, etc.).

KillVir UV-C air disinfection is unique in that it works in the presence of people and continuously spraying disinfectant solutions must not be used in the presence of persons (there is a risk of reduces the microbiological load in the room. Conversely, disinfection with ozone or by poisoning and other health risks) and must therefore be applied only after all-day operation. During operation, however, there is a continuous increase in the microbiological load in the room to which people are exposed inside. Chemicals or ozone also act on surfaces, but they can also have degrading effects. In terms of different effects and application time, these methods can effectively complement each other.

• highest UV-C performance, efficiency and durability
• the values ​​of the UV-C energy doses provided by the individual types of the device and the doses needed to inactivate the individual pathogens are given, so the appropriate type can be chosen exactly
• immediate elimination of pathogenic microorganisms as they pass through the device
• unrestricted presence of persons
• absence of contaminated waste
• tight passage of contaminated air around UV-C lamps ensures a high dose
  irradiation for the effective elimination of pathogenic microorganisms
• powerful fans for efficient room air circulation
• made from premium Philips components, UV-C tube life 18,000 operating hours (approx. 2 years of continuous operation)
• the dust filter prevents contamination of the internal reflecting surfaces of the device and thus of sagging
  effectiveness
• all-stainless steel design – representative appearance and easy cleaning

Watt is a unit of power, ie the amount of energy delivered per unit of time. The joule is a unit of the amount of energy. For disinfection purposes, their density is decisive, so it is necessary to apply them to an area of 1 m2. The radiation power incident per 1 m2 is called the radiation density E and its unit is W / m2. The energy of radiation that fell during the exposure time t per 1m2 is called the dose H. It is the product of the radiation density E and the exposure time t, ie:

H = E x t,

The dose has the unit Ws/m2 = J/m2.

When disinfecting with UV-C radiation, it should of course be the energy radiated in the UV-C region. Conventional UV-C emitters in this area emit approximately 1/3 of their total power!

Ozone is a highly reactive gas (a strong oxidant). It is naturally found in the high layers of the atmosphere, where it protects us from the penetration of UV-C radiation from the sun. In the ground layers of the atmosphere, it is created when the sun’s rays shine into the air air polluted by human activity. However, its stability is low, its lifespan is in units of seconds and it decomposes into normal oxygen. However, new ozone molecules are still being formed under suitable conditions. In the indoors conditions, this is an undesirable immission because it is harmful to human health.

With sufficient concentration, it kills all microorganisms, so it is also used for disinfection. During this disinfection, the presence of people is excluded and the room must then be thoroughly ventilated. The corrosive effects of ozone must also be taken into account.

Ozone is generally produced when UV emitters work. It causes UV radiation with wavelengths below 240 nm. The extent to which these wavelengths can be filtered out (special types of glass, filters…), the extent to which the formation of ozone by UV sources is suppressed. For UV-C tubes used in AEROTERM’s KillVir, the ozone concentration is below the limit of quantification.