National and Kapodistrian University of Athens

 

                                                                        CIRCULAR

 

 

SUBJECT: Taking measures to safeguard Public Health from viral and other infections during the use of air conditioning units.

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Re: 1. The D1(d)/ PG oik.19957/20-03-2020 "Taking measures to safeguard Public Health from viral and other infections during the use of air conditioning units in Health Units (AD: 9ΙΥΥ465ΤHYO-9ΙΣ)

 

2. Information from ECDC on how the SARS-CoV-2 virus spreads (Website: https://www.ecdc.europa.eu/en/novel-coronaviruschina/questions-answers)

 

3. The technical text "How to operate and use building services in order to prevent the spread of the coronavirus disease (COVID-19) virus (SARS-CoV-2) in workplaces, April 03 2020" by REHVA (Federation of European Heating , Ventilation and Air Conditioning Associations)

 

4. Internal communication with the Directorate of Technical Services of the Ministry of Health

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1. GENERAL

 

In continuation of (1) related circular on the occasion of the spread of the SARS CoV-2 virus in our country and taking into account the above 2, 3 and 4, we inform you of the following:

 

Coronaviruses are a group of viruses that commonly cause respiratory infections, the severity of which varies in humans and animals. It is estimated that about one-third of upper respiratory infections in humans may be caused by coronaviruses. The SARS CoV-2 coronavirus is a strain isolated for the first time in humans.

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Based on the available epidemiological data, it appears that the SARS CoV-2 coronavirus is likely to be transmitted from person to person through droplets emitted by a sick person, through coughing or sneezing, or by direct or indirect contact with respiratory secretions (ie through contaminated hands). The incubation time of the disease is estimated at 2-14 days with an average incubation time of 5 days.

 

The transmission mechanisms of SARS CoV-2 exposure through the air are as follows:

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•  Transmission via large droplets / particles (>10 microns) in close contact where the released droplets land on surfaces within 1-2 meters of the infected person at most. People can become infected after touching contaminated surfaces and then touching their eyes, nose or mouth. But they can also be infected by directly inhaling infected droplets that come from sneezing or coughing or from the exhalation of an infected person, as long as they stand at a distance of 1-2 meters from him.

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•    Airborne transmission via small particles (<5 microns), which can remain in the air for hours and can be transported over long distances. These are also created by coughing, sneezing and talking. Such small virus particles remain airborne and can travel long distances and are carried by air currents in rooms or in the exhaust ducts of ventilation systems

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2. PROTECTION MEASURES 2.1.

 

OBJECTIVE The proposed protection measures aim to limit the mechanical spread of the virus through the air currents developed during the operation of the air conditioning units. It is clarified that it has not been established that the 3 air conditioning units per se do not act as foci of growth and multiplication of the virus (therefore in a house/office where the residents or workers are all healthy there is no risk of infection). Air conditioning units may, however, under conditions facilitate airborne transmission by mechanical means from persons who are already carriers. Depending on the type of unit the recommended measures may differ.

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2.2. RECOMMENDATIONS FOR TECHNICAL MEASURES Aiming to reduce as much as possible the residence time of air in a room, the following points are highlighted regarding the use of air conditioners in buildings, where this is possible:

 

•  Increasing the supply of fresh air to all central air conditioning units (CHUs)

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•  Complete avoidance of air recirculation

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•  Continuous operation of the PPEs (24/7) even if the part they supply is not working (to avoid the proliferation of microorganisms)

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• In PPEs with rotary air exchangers, their rotation should be stopped and if possible the air should be discharged without passing through the exchanger. Plate heat exchangers to be decommissioned if possible (although their degree of danger is not sufficiently documented)

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• In air recirculating air handling units, the mixing dampers should be closed and the return air discharged directly to the outside environment

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•  Discharge vents should be as far away from fresh air intake points as possible

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•  Fan coil units (FCU) where possible, to be taken out of service or when this is not possible to be put into continuous operation 24/7 (for reasons of avoiding resuspension of viruses in case of interruption and restart of units)

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• the domestic type units (split units) where possible, to be similarly put out of operation or when this is not possible to be put into continuous operation 24/7 with a parallel operation of natural ventilation

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• Set the ventilation to the speed indicated by the manufacturer at least 2 hours before the time of building use and change to a lower speed 2 hours after the time of building use

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•  At nights, weekends and holidays it is not recommended to turn off the ventilation, but to keep the ventilation systems running but at a lower speed

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•  Avoid changing set heating, cooling and potential humidity levels

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•  Avoid scheduling pipeline cleanup at this time. Airway cleaning should be encouraged if it is done by mechanical means (robots)

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•  For KCMs and split units, the filters will be replaced according to the normal procedure according to the scheduled maintenance. Regular filter replacement and maintenance operations will be performed using and taking all protective measures (personal protection, room ventilation, safe disposal of replaced filters) including respiratory protection.

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• Ensuring adequate ventilation of all spaces with outside air.

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3. OTHER INSTRUCTIONS

 

In the context of broader health protection, the following are highlighted:

 

•  Advise building users to empty toilet bowls with the lid closed. This is to limit aerosol transmission from the toilet at the time of emptying

 

•  Continuous operation of WC fans. In the case where the operation of the fan is connected to the operation of the light switch, disconnect it if possible

 

•  Systematic taking of all appropriate measures for the proper operation of air conditioning facilities and avoiding the creation of foci of contamination by other microorganisms

 

•  In any case, it is pointed out again that care should be taken for the continuous or at least systematic natural ventilation of the space through openings (windows, external doors) even with the parallel use of air conditioners.

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