My questions are about the safety of central air conditioning. The Guidelines mention that at some places like office buildings and hotels, central air conditioning can completely avoid the risk of virus transmission through the ventilation system. I want to know more about this. In addition, some places have stressed the sanitation of cooling water and condensate water in the use of centralized air conditioning, while others did not. How should the management of condensate water be strengthened? Thank you.
Thank you for your questions. These Guidelines are specifically for summer, so air conditioning is a very important aspect. We added guidance on the use of central air conditioning systems on the basis of the previous version. It should be said that central air conditioning alone cannot completely prevent the virus from spreading through the ventilation system. If there is a virus present, there will still be certain risks. However, we mentioned three aspects to contain the risks in the guidelines:
First, before turning on an air conditioner — which means before use — we should check the machine to see if it runs properly and has a proper distance between the air intake and outlet. We need to clean up the cooling tower and make sure the fresh air intake is clean.
Second, in the course of its operation, we should maximize the fresh air intake and reduce the return air. Completely shutting off the return air is very hard to achieve, so we advise reducing the return air as much as possible and increasing fresh air intake.
Third is strengthening the sanitation management of cooling water and condensate water. We must make sure to regularly clean, disinfect or replace necessary equipment and components, such as the air supply vents. This is based on the general situation. Of course, when there are confirmed cases of COVID-19, we should also clean and disinfect central-air conditioners, and they may only be restarted after hygienic evaluation.
Regarding the cooling water and condensate water we mentioned, some of the central air condition systems don't produce cooling water and condensate water during operation. These are mainly the multi-split type air conditioners, which have a system composed of an outdoor unit that connects several indoor units. This type of air conditioner performs the functions of heating and cooling with the help of refrigerant. In the process of operation, they don't produce cooling water and condensate water. That's how it works.
In this process, it is important to clean, disinfect and replace pieces of equipment like the air supply vents. Why do we propose to strengthen the sanitation management of cooling water and condensate water? Cooling water mainly comes from parts that include air-handling units and surface-air coolers in the fan coil units, which are prone to breeding microorganisms that can affect indoor air quality and pose potential risks. Therefore, we should clean and disinfect cooling water containers at regular intervals.