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JACA (Japan Air Cleaning Association)

The Abstracts of the paper carried by the Journal of JACA

vol.58-3(2020/9/30)

Approach to infection control of novel coronavirus in buildings

In this paper, the author shows approaches to infection control of novel coronavirus in buildings based on the reports and opinions till June 2020, by the sectors on measures against the novel coronavirus disease (COVID-19) in the Ministry of Health, Labour and Welfare, the World Health Organization, the Architectural Institure of Japan, the Society of Heating, Air-conditioning and Sanitary Engineering of Japan and researchers in the world. At first, the relationship between the lack of ventilation rate and the airborne infection with splash and the influence of humidity upon infection have been investigated considering with the characteristics of infected cluster spaces. Secondly, the increase of virus infection risks has been pointed out based on the increase of nonconformity rate to the standard of indoor carbon dioxide concentrations in buildings. Finally, the author has organized the measures against novel coronavirus infection and show the future tasks. (investigations on indoor environment in the infected cluster spaces, experiments on the influences of indoor temperature and humidity upon novel coronavirus infection.)

Environmental factors involved in SARS-CoV-2 transmission

Coronavirus disease 2019 (COVID-19), has caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a new pandemic infectious disease. SARS-CoV-2 is spread primarily via respiratory droplets during close person-to-person contact in environment. Infection can be spread by asymptomatic, presymptomatic, and symptomatic carriers. This article summarizes environmental factors involved in SARS-CoV-2 transmission. SARS-CoV-2 can presist on surfaces for at least 3 days and on the surface of a surgical mask for up to 7 days depending on conditions. If SARS-CoV-2 is aerosolied intentionally, it’s stable for at least several hours. SARS-CoV-2 on surfaces of objects is inactivated rapidly with sunlight. Most studies reported a positive association with the air pollution. However, the association with climate conditions, including ambient air temperature and humidity, has not been consistent and are controversial. Therefore, the seasonality of COVID-19 infection is unknown. Further researches that are well-designed and well-constructed are required.

Possible pathways of SARS-CoV-2 transmission and characteristics of droplet nuclei

WHO insists that the transmission of the COVID-19 can be mainly occurred by direct contact via infected people and indirect contact via surfaces in the immediate environment or with objects used by the infected person, not by airborne transmission through small airborne particles. But it is important for discussing airborne transmission of SARS-CoV-2 to understand the characteristics of droplet nuclei emitted by cough and speech in indoor environments. This report briefly describes size distribution of droplet, emission rate of droplet by cough and speech and resuspension of deposited particles on floor surfaces.

Cases of infection in which environmental factors seem to have promoted infection

Cases of COVID-19 outbreaks have shown that in confined and enclosed spaces with poor ventilation, crowded places, and close-contact settings where people have close-range conversations, a large number of people can be infected by aerosol particles containing the infectious virus. SARS-CoV-2 is unlikely to be detected in air samples from spaces with adequate ventilation and in uncrowded environment. In addition to practicing hand hygiene and wearing masks with proper timing, it is important to encourage ventilation as a preventive measure against COVID-19. Future investigations of the indoor environment, ventilation rates, and operation of ventilation and air-conditioning equipment are strongly required to determine the relative contribution of each route of infection and the minimum ventilation rate required for infection control.

Role of HVAC system and UVGI in infectious aerosols control

Today, more than 15 million infected people with COVID-19 are globally confirmed and more than 0.63 million people have died among them. WHO has described the transmission of SARS-CoV-2 as follows: current evidence suggests that transmission of SARS-CoV-2 occurs primarily between people through direct, indirect, or close contact with infected people through infected secretions such as saliva and resporatory secretions, or through their respiratory droplets, which are expelled when an infected person coughs, sneezes, talks or sings. Some outbreak reports related to indoor crowded spaces have suggested the possibility of aerosol transmission, combined with droplet transmission, for example, during choir practice, in restaurants or in fitness classes. This article describes the role of HVAC system and UVGI (Ultraviolet Germicidal Irradiation) in infectious aerosols control.

Air filters and related equipment for prevent of infection

Ventilation and airflow control have become important as the infection preventive measures against the new coronavirus SARS-CoV-2, these virus causes COVID-19. In this article, we will be discussing the details of preventive measures using air filters, including the exapmles using industrial air filters installed in the office buildings and commercial facilities, actual examples of antivirus equipment for medical institutions, hospitals, clinics, and home air purifier.

Ventilation and air conditioning for office buildings

Ventilation means the intake of outdoor air into a room to dilute the pollutants generated in the room, and are usually combined with air conditioning to control temperature and humidity. In addition, these facilities maintain the health and agreements by the difference between indoor and outdoor in air quality, so that it expect the amount of intake of outside air with the difference of temperature and humidity. The relationship between the amount of outside air required for legal ventilation of office buildings including office buildings and the indoor temperature and humidity adjustment considering energy saving has been described.