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AC Spread Covid-19? A Case in China.

The failure of the Air-conditioning system (AC) not ventilating and filtering the circulating indoor air of a restaurant in China.


In this case, ten seated at the back of the restaurant became sick, while those seated at the front were not affected. One infected person through respiration (normal breathing or sneezes) releases droplets in the air, carried along by the AC stimulated air movements, re-circulated within the gray area at the back, and people seated in proximity were exposed.


There were four ductless split units without fresh air features, with only one (1) air inlet at the far front end of the premise and one (1) exhaust outlet close-up inside the toilet.  So, there was no exhausting and fresh air to ventilate the indoor air.


The time-averaged ventilation rate per person in that restaurant was 0.9 L/s (less than 2 CFM). Based on ASHRAE’s 62.2 standards, the suggested minimum per person is 7.5CFM which was way too low.

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The sealed-up AC building traps pollutants indoors that need to be diluted with outdoor fresh air, O2 while exhausting the high pollutant (PM2.5, CO2, TVOC) indoor air, and balances the indoor air pressure to create air movements. 


Indoor air is presumably more polluted than outdoor in natural conditions, but not so in an urban industrialized environment. The rising concern is whether the outdoor fresh air has lesser discrepancy i.e., PM2.5, germs, humidity, and temperature when brought into an AC environment.


Fresh Air System, which is gaining attention from local authorities predominantly related to compliances for buildings and business premises related to Sick Building Syndrome and Covid precautions. It is an inevitable application for comfort and occupants’ health and safety. 


There are many applauded professionally written research out there that can be intimidating to the public and users. Hence, this presentation is a snippet overview of the Fresh Air System to assist in general decisions making.


Minimize the spread of Coronavirus. What can SMEs and Homeowners do?

  1. How Filters Trap Airborne Bacteria and Viruses?

  2. Are UV lights effective in killing germs?

  3. How Humidity Control Improves Indoor Air Quality?

  4. What is a Fresh Air System and ERV?

  5. Indoor Air Purification. What Options We Have?

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