No ventilation system in office? Open windows, turn off air-con

If your office does not have a mechanical ventilation system to provide fresh air, you should now open all the windows and doors as often as possible.

And the air-conditioning should be reduced or turned off when this is happening, said three government bodies in a set of updated guidelines on improving building ventilation and air quality to prevent the spread of Covid-19.

The new directive comes as Singapore sees an uptick in coronavirus cases in the community, with 21 locally transmitted cases reported yesterday.

In the five-page document, jointly issued by the Building and Construction Authority, National Environment Agency and Ministry of Health, the authorities noted that Covid-19 can be spread by virus aerosols in enclosed environments that are poorly ventilated.

"Thus, it is critical to mitigate this risk by improving ventilation and air quality in indoor environments," they said.

The guidelines set out measures that building owners and facility managers should undertake in three kinds of settings.

For air-conditioned spaces with mechanical ventilation - such as office blocks and shopping malls - those in charge should make sure that the ventilation systems are in good working order and maximise the intake of outdoor air.

Air should be purged at least once a day before the building is occupied, and indoor air recirculation reduced. To expel indoor air, exhaust fans should also be running at full capacity in areas such as toilets.

Spaces without mechanical ventilation - such as retail shops - should have their doors and windows opened as frequently as possible, and operators should consider installing window-mounted exhaust fans.

In enclosed spaces, where the risk of disease transmission is high, portable air cleaners with high-efficiency filters may be considered as an interim measure. Such spaces include dental clinics or premises where Covid-19 patients may be present.

For naturally ventilated premises such as coffee shops and dormitories, operators should keep the windows and doors open at all times, with outward-facing fans installed to increase air exchange. They should check other systems - including water seals in the sanitary system - to make sure there is no undesired air leakage into occupied spaces.

These measures should not exist in isolation, the authorities said. High-touch points should be regularly disinfected and building occupants should still abide by safe distancing measures and wear masks.

Public buses and trains are well ventilated, according to a study conducted last year by the Agency for Science, Technology and Research.

The study found that air in trains is exchanged every six minutes through ventilation systems, and when doors open and close at each station. In buses, fresh air enters when doors open and close. Buses are also ventilated at interchanges when their doors are kept open.

"The ventilation systems, combined with stepped-up cleaning and disinfection regimes - as well as commuters' observing the strict discipline of wearing good-efficiency masks and not talking - will minimise commuters' exposure to the virus," the authorities said.