UV irradiators

The main way viruses like MERS (Middle East Respiratory Syndrome) and SARS (Severe Acute Respiratory Syndrome) spread is from one person to another in tiny moisture particles called aerosols. What's more, new research shows that the most virulent SARS-CoV-2 alpha and delta variants are mutating towards more efficient airborne transmission and infection in humans.

how to prevent the spread of pathogenic particles

How can we prevent the spread of pathogenic particles in indoor air while still allowing people to be active without any restrictions?

The simplest and most reliable solution to this problem remains regular ventilation of the premises, proposed many years ago by the Russian military surgeon N.I. Pirogov. In modern practice, this principle is often implemented by providing forced ventilation of premises. Air exchange is a quantitative parameter characterizing the operation of the ventilation system. The intensity of air exchange is measured by the multiplicity - the ratio of the volume of supplied or removed air in one hour to the volume of the room. The ratio of supply or exhaust air is determined by the standards, for example, SNiP 31-06-2009 "Public buildings and structures" or for medical organizations, SP 158.13330.2014.

The formula for the air exchange rate looks like this:
Nvent = Qair / Vroom
Nvent – air exchange rate 1/hour;
Qair - the supplied amount of fresh air per hour, m3/h; Vroom - the volume of the room, m3.

For ordinary office premises, the value of 40 m3/h is considered sufficient. air per employee, if possible, periodically ventilate the room through window sashes, transoms, vents or 60 m3/h. per employee, if this is not possible (SP 60.13330.2016).

Accordingly, in order to reduce the concentration of polluting particles and the likelihood of the spread of viruses in the room, it is necessary to increase the ventilation performance and the air exchange rate. To effectively reduce airborne transmission of SARS-CoV-2 in small spaces (eg classrooms, retail stores, etc.), air exchange rates should be at least 4-6 times per hour.

It is clear that an increase in the air exchange rate standards leads to an increase in the cost of modernizing and maintaining ventilation and air conditioning systems, it takes time to design, purchase equipment, carry out work, and suspend the activities of the institution, which ultimately makes such an approach unrealistic.

smart recycling

To ensure the microbiological purity of the air environment in real conditions, it is advisable to use hybrid air preparation schemes that combine the available room ventilation capabilities with air recirculation by devices with a disinfection function. Such devices can be local bactericidal air cleaners based on ultraviolet C radiation (UV recirculators) or photocatalysis.

Advantages of this approach:

epidemiological safety is ensured, the possibility of unhindered vigorous activity for a person remains;
UV disinfection is environmentally friendly, does not involve the use of chemicals;
proven effectiveness of UV disinfection against all germs and viruses, including COVID-19 (including any new strains);
UV radiation does not create carcinogenic disinfection by-products such as chlorine;
after processing, no chemicals remain and, therefore, the formation of new superbugs is excluded;
no danger of overdose;
the disinfection process is absolutely controllable, there is the possibility of working in automatic mode, as well as the ability to control using building engineering systems;
reliability and ease of maintenance of UV devices.

The most expedient scheme for the use of local UV recirculators is their combined use with supply and exhaust ventilation. At the same time, a hybrid scheme of smart air preparation is implemented, when the performance of recirculation air cleaners with a high bactericidal efficiency of up to 99.9% is added to the ventilation air exchange.

It is possible to determine the total bactericidal performance of air exchange, expressed in equivalent air exchange rate - Neq:
Neqv = Nvent + Mochs
Neqv - equivalent air exchange rate;
Nvent – air exchange rate 1/h;
Mochs (m3/h) - the performance of recirculators in terms of the volume of air disinfected with high efficiency.

Accordingly, in the case of a hybrid air exchange scheme, the equivalent volume of clean air entering the room will increase without increasing the performance of the ventilation system!

For example, if the existing air ventilation system provides an air exchange rate of 3 for a room of 50 cubic meters, then additionally using a SANITAR 230 UV recirculator in this room with a capacity of 100 cubic meters / h. (air exchange rate - 2 in a room of 50 cubic meters), you can get an equivalent air exchange rate equal to 5. Achieving this rate is practically a target for ensuring epidemic safety in the room. At the same time, the time for preparing the premises and energy costs are significantly reduced.

Thus, when implementing a hybrid smart recirculation scheme, the epidemic safety of the premises is ensured without expensive modernization of the ventilation system. The placement of additional local recirculators in the room that disinfect the air allows you to increase the equivalent air exchange, to implement a pragmatic and economical solution to combat the spread of infection.

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