Study of the effectiveness of the use of closed-type UV-recirculators for air disinfection in enclosed space

Introduction. The research is devoted to assessing the results of our studies of indoor air concerning microbial contamination during the operation of a UV recirculator with different modes (different UV doses). Also, a theoretical calculation of the influence of the ratio of the capacity of the UV recirculator to the air volume of the treated room on the efficiency of air disinfection has been made. Materials and methods. The study of indoor air in terms of total bacterial count (TBC), including coccal microflora and yeast and mould fungi, were carried out. Air sampling and evaluation were carried out under the requirements of Methodical guidelines MUK 4.2.2942-11 “Methods of sanitary and bacteriological studies of environmental objects, air and sterility control in medical institutions”. The evaluation of the results was carried out following R 3.5.1904-04, "The use of ultraviolet bactericidal radiation for disinfection of indoor air". During the study, agar culture media were used: Sabouraud agar, yolk-salt agar (YSA), meat-peptone agar (MPA), nutrient agar with the addition of 5% sheep blood (blood agar), bismuth sulfite agar, XLD-agar, cetrimide-agar, “Shine” agar, Endo agar. Results. As a result of the studies carried out, it was shown that a dose of UV irradiation of the order of 12-15 mJ/cm2 leads to an insignificant change in the concentration of bacteria (TBC) and fungi in the air (the efficiency was 58% and 69%, respectively). UV doses of the order of 25-30 mJ/cm2 significantly reduce the concentration of bacteria (TBC) and fungi in the air (efficiency was 99.99% and 99.4%, respectively). A theoretical calculation showed that it is practical to use a UV recirculator of such a capacity that provides an air exchange rate in the room of at least 4 (with ventilation operating at a rate of at least 2). Conclusion. To effectively use UV recirculators in enclosed spaces against bacteria and fungi, it is necessary to use models that provide a UV dose of at least 25-30 mJ/cm2. In contrast, their air capacity should provide an air exchange rate of at least 4.

Air ozonization for prevention of bacterial and viral infections

Objective. To assess the effectiveness of the low-dose air ozonation for disinfection of the air in the working room. Materials and methods. We investigated 90 air samples (3 samples were taken weekly before and after the production meeting using the automatic sampling device of biological aerosols of air PU-1B). The total bacterial contamination, the content of staphylococci and mold spores were determined. Ozonation of the room (83.3 m3) was carried out for 20 minutes by means of domestic ozonator. The accumulated dose of ozone was 133.3 mg (1.6 mg/m3). Statistical data processing was carried out using the MedStat licensed program. The median, median error (Me me), left and right 95 % confidence intervals (95 % CI) were calculated. Paired comparisons were made using Wilcoxon's T-test. Results. After the meeting, the total bacterial contamination of the air was 56.0 9.3 (47.078.0) CFU. The content of staphylococci and mold spores in the air was 85.5 12.5 (76.0100.0) and 44.5 6.5 (32.054.0) CFU, respectively. After ozonation, the total bacterial contamination of the air was 14.5 3.6 (10.021.0) CFU. The content of staphylococci and mold spores in the air after ozonation was 35.5 6.7 (25.052.0) and 26.0 5.0 (18.032.0) CFU, respectively. Ozonation of the room provided a significant decrease (p 0.001) in all three of the above indicators. The room ozonation carried out promoted a reliable decrease (p 0.001) in all the above mentioned parameters. Conclusions. The above data and analysis of the literature show the possibility of using low doses of ozone for the prevention of bacterial, fungal and viral infections including SARS-CoV-2. Further study and development of reasonable modes of ozone disinfection, including low doses of ozone, is needed, as well as determination of the efficiency degree of air disinfection with non-toxic gas concentrations.

Bactericidal efficiency of preparation based on essential oils used in aerosol disinfection in the presence of poultry

A disinfectant was created for aerosol disinfection of premises in the presence of poultry, which will help reduce microbial contamination of premises, increase survival, weight of poultry and economic efficiency of meat production in general. The preparation based on essential oils can be used for disinfection in the presence of poultry and at the same time exhibits a therapeutic and prophylactic effect on respiratory infections. This disinfectant has a colloidal solution of silver (Ag), benzalkonium chloride and essential oils of thyme, fir and eucalyptus. The preparation based on essential oils contains (per 100 g): benzalkonium chloride – 16.0 g; thyme oil – up to 2.0 g; eucalyptus oil – up to 2.0 g; fir oil – up to 2.0 g; colloidal solution of silver (Ag) – 20–30 mg; distilled water - up to 100 cm3. Aerosol sanitation of indoor air was carried out with 0.3% solution of preparation in the period before housing poultry and once a day from the 20th to the 35th day of growing broilers with aerosol cold mist generator Dyna-Fog Tornado (model 2897, construction type – ULV-electric spray gnerator, manufacturer – Curtis Dyna-Fog, Ltd., USA) at a dose of 50.0 cm3 per 1 m3 at an exposure of 60 minutes. The size of the aerosol particles is 20 μm. On days 1, 4, 8, 11, 15, 28, 37, and 42, the chickens were weighed, and the blood was taken for examination. Blood was examined to study the number of red blood cells, hemoglobin content, the bactericidal activity of blood serum, phagocyte activity of leukocytes, lysozyme activity of blood serum. According to the results of the research, the technological modes of air disinfection of poultry premises in the presence of broiler chickens were substantiated during the use of preparation, which contains nanoparticles (NP) of silver, benzalkonium chloride and essential oils. The optimal mode of aerosol treatment of poultry houses using a 0.3% solution preparation based on essential oils is 50 mL/m3 of a room with a 60-minute exposure. The use of air disinfection in the presence of chickens during broiler rearing and one treatment per day from 20 to 35 days of the chickens’ growth reduced the microbial pollution of indoor air. Thus, the concentration of microbial cells in the room where the chickens were kept was 230.2 ± 15.6 thousand microbial cell/m3. Sixty minutes after disinfection, the concentration decreased to 1.4 ± 0.4 thousand microbial cell/m3. In addition, the bodyweight of chickens at 6 weeks increased by 449.4 ± 16.3 g (15.9%) compared with the controls. The method and mode of air treatment did not adversely affect the development of the internal organs of the poultry and their physiological state, which is confirmed by studies of the morphological parameters of the chicken blood. The data obtained indicate a positive effect of the developed methods and modes of aerosol air treatment with the preparation based on essential oils on the growth and development of broilers.

Improved estimates of 222 nm far-UVC susceptibility for aerosolized human coronavirus via a validated high-fidelity coupled radiation-CFD code

Transmission of SARS-CoV-2 by aerosols has played a significant role in the rapid spread of COVID-19 across the globe. Indoor environments with inadequate ventilation pose a serious infection risk. Whilst vaccines suppress transmission, they are not 100% effective and the risk from variants and new viruses always remains. Consequently, many efforts have focused on ways to disinfect air. One such method involves use of minimally hazardous 222 nm far-UVC light. Whilst a small number of controlled experimental studies have been conducted, determining the efficacy of this approach is difficult because chamber or room geometry, and the air flow within them, influences both far-UVC illumination and aerosol dwell times. Fortunately, computational multiphysics modelling allows the inadequacy of dose-averaged assessment of viral inactivation to be overcome in these complex situations. This article presents the first validation of the WYVERN radiation-CFD code for far-UVC air-disinfection against survival fraction measurements, and the first measurement-informed modelling approach to estimating far-UVC susceptibility of viruses in air. As well as demonstrating the reliability of the code, at circa 70% higher, our findings indicate that aerosolized human coronaviruses are significantly more susceptible to far-UVC than previously thought.

Design concept of onboard air purification system for commercial aircraft

The purpose of the article is to discuss methods of air disinfection in passenger aircraft cabins during flight. In the course of the study, a comparative analysis of modern methods of cleaning and disinfecting air in closed rooms was carried out. The efficiency, mass characteristics and energy consumption of UV sources are compared. The use of photocatalytic filters based on the phenomenon of oxidation of organic substances under the influence of sunlight in the presence of a catalyst is proposed. As a result, the authors compare the efficiency of disinfection and energy consumption when using various methods of air purification. In addition, the authors draw conclusions about the prospects of the proposed method of air disinfection using photocatalytic filters in relation to the cabins of passenger aircrafts. The schemes of rational placement of UV sources are proposed, which allow obtaining the maximum efficiency of air disinfection.

Development and verification of a test rig for inactivation of bacteria and (corona-) viruses by UVC air disinfection systems

The ongoing coronavirus pandemic spreads through airborne transmission and is therefore difficult to contain. However, coronaviruses are highly sensitive to UVC, so UVC air disinfection systems should be able to inactivate the virus. Unfortunately, so far there are only few possibilities to test the reduction of airborne viruses or other pathogens. A special test rig, which mainly consisted of a nebulizer and an airflow system, was developed to determine the antiviral and antibacterial efficiency of UVC air disinfection systems. In the assessment of such an UVC air disinfection system with nebulized Staphylococcus carnosus and a sampling period of 30 minutes, a mean bactericidal reduction of 3.70 log10 (99.98 %) was determined. For antiviral irradiation of the coronavirus surrogate phi6 a mean viral load reduction of 1.18 log10 (93.40 %) was observed after a sampling period of 10 minutes. Therefore, mobile UVC air disinfection systems could be applied in hospitals, retirement and nursing homes.