CityU air vents foil virus

Top News | Mandy Zheng 4 May 2020

An innovative ventilation system that can reduce the risks of Covid-19 infection by supplying fresher air to medical staff in isolation wards has been developed by the City University.

The stratum ventilation system has an original design, with its air supply and exhaust vents being installed in different positions and heights, to minimize the possibility of fresh air mixing with air to be discharged. The commonly used mixing ventilation system usually has both vents at the ceiling.

In a hospital ward, the supply terminal's recommended placement is 1.5 meters above the floor, which is about the height of one's nose from the ground when a person is standing.

The exhaust terminal is to be put close to the floor near patients' headboards, so that the air prone to contain pathogens will be expelled right away.

"The system allows the fresh air to first reach the breathing zone of the health-care workers, and then to that of the patients," said developer John Lin Zhang.

"This not only positions health-care workers in the 'upstream' part of the supply airflow, but also dilutes and expels the airborne contaminants in the ward effectively," the professor said.

"In addition to personal protective equipment, the stratum ventilation system will provide double protection for health-care workers."

The professor's hope is for frontline workers fighting the epidemic to be protected.

Lin, who heads the division of building science and technology, found in simulation tests that his product was able to lower the concentration and distribution level of droplets after a patient coughed in an isolation ward, outperforming other devices.

His experiments also showed that when other systems were adopted, part of the routes people took in wards were contaminated, posing a high risk of infection for staff who stay or pass through this area.

The problem with the conventional design of vents was that it let the supply and exhaust airflow blend together.

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