Four of the 12 environmental samples collected from various locations at Heng Tai House, Fu Heng Estate where three COVID-19 patients live have tested positive, the Government said today.

The samples were collected from the two units where the patients live and the rooftop of Heng Tai House, as part of the Centre for Health Protection’s epidemiological investigations on the three confirmed cases there.

The four positive samples were collected near the water closet of the patients' units on the 32nd floor and 34th floor, and from inside the open end of the rooftop ventilating pipe for Unit 13’s foul water stack.

An interdepartmental meeting was conducted this morning to examine the test results.

The Government said Heng Tai House's building, drainage system and ventilating pipe designs comply with Buildings Ordinance requirements, related regulations as well as environmental and health safety standards.

According to the preliminary analysis, the virus found near the water closets likely remained after the patients had used the toilet.

As for the virus found inside the rooftop ventilating pipe, it is suspected that the height difference between Unit 13’s rooftop parapet and Unit 14 might be relatively conducive to cause a wake effect in the re-entrant of top floors in the building.

However, the combination of building orientation, roof design, wind speed and direction is essential in bringing the virus into residential units from the rooftop ventilating pipe by air turbulence.

Even if the wake effect might have occurred, the concerned government departments consider the circumstances an isolated case and uncommon.

For safety's sake, the Government will set up an interdepartmental expert group as soon as possible to follow up on the issue.