SINGAPORE: Improving ventilation and the flow of fresh air inside buildings could help to prevent the concentration of aerosol particles, though experts that CNA spoke to had differing views on how effective this would be in reducing COVID-19 transmission.
On Tuesday (May 25), authorities issued updated guidelines for building owners and facility managers on enhancing ventilation and air quality in indoor spaces, aimed at helping to tackle a growing number of COVID-19 cases in the community.
It spelled out measures such as keeping windows and doors open at all times in premises that are not air-conditioned, and installing outward-facing fans to increase air exchange.
For premises that are air-conditioned, authorities said they should ensure that their ventilation systems are in good working order and set to maximise the intake of outdoor air. Air should be purged at least once a day, and more frequently at higher-risk areas.
Weighing in on the new guidelines, Professor Dale Fisher, a senior consultant at the National University Hospital’s division of infectious disease, said some transmission could be prevented with good ventilation and air quality.
“Imagine if there was a certain number of particles in a small space but there was good ventilation, the doors were open and the fans were blowing them out, that same number of aerosol particles (would) be more widely spread, diluting them instead of being concentrated in one area," he said.
“Then, the chance of an infective dose getting to a person is much reduced,” said Prof Fisher, who is also chair of the national infection prevention and control committee at the Ministry of Health (MOH).
Similarly, Professor Teo Yik Ying, dean of the National University of Singapore's Saw Swee Hock School of Public Health, agreed that improving air flow circulation in buildings, especially those which are currently poorly ventilated, could “certainly” reduce the risk of airborne transmission.
“In enclosed environments that rely on mechanical ventilation, there will be parts of the enclosed area where the circulation of air is poorer, and that can increase the risk of airborne transmission of Covid-19,” he said.
Having good ventilation could even “marginally” help to reduce the risk of transmission through droplets by drying them up, noted Prof Teo.
However, Professor Paul Tambyah, president of the Asia Pacific Society of Clinical Microbiology and Infection, was doubtful that it would make much of an impact.
“I think that the benefit will be very limited,” he said, adding that there is no evidence, currently, that airborne transmission is a "major route" of transmission.
“But perhaps if individuals get fresh air, they are less likely to cough or sneeze and thus less likely to spread the virus to others around them,” he said, adding that getting some fresh air could also make current restrictions a bit more tolerable.
Prof Teo also said that more insights from ongoing epidemiological investigations will be needed, as it is currently unclear how common Covid-19 transmission is attributed to poor ventilation, rather than from close interactions between people or from contaminated surfaces.
At Tan Tock Seng Hospital, wards have also been fitted with HEPA filters and exhausted fans to enhance ventilation and airflow, following an outbreak of COVID-19. The hospital said previously that it can achieve at least six to 12 air changes per hour with the new features, preventing a build-up of stagnant air in cubicles.
READ: Authorities studying possibility of airflow and ventilation issues at Tan Tock Seng Hospital ward
Such measures may be less relevant in a domestic setting, the experts said.
“By and large, the spread in households (is) mainly attributed to contact, droplets, and surfaces,” said Prof Teo.
“It is really difficult to prevent transmission within people living in a same household, and this is why worldwide, we have seen household transmission to be the dominant mode of transmission,” he explained.
“It is also why it has been so difficult to break the chains of transmission in the migrant worker dormitories,” said Prof Teo, adding that such premises typically house a large number of people sharing common facilities.
“The honest truth is, if someone in your household has COVID, then it's probably not going to make a big difference because there's going to be so many other opportunities to catch COVID If it's your husband, wife, mother, father, just from contaminated environments and droplets spread and things like that,” said Prof Fisher.
“The main measure at home is to not go out unless you really have to,” he added.
“WHOLE PACKAGE” NEEDED TO REDUCE COVID-19 TRANSMISSION
Ultimately, curbing the spread of COVID-19 cannot rely solely on good air quality, said Prof Fisher.
Instead, what is needed is the “whole package”, he said.
“Whether it's mask wearing or testing, or QR codes or all the other various measures, I think we just need to be doing what we have to do and make sure we do it very, very strictly,” he said.
“Don’t sneak off and have lunch with all your friends, because that’s really contrary to the spirit of what we're trying to do now.”
“If we can think of other things that could help, then, we should do everything that is possible and feasible,” he added.
Good respiratory etiquette, such as how to cough and sneeze, strict hand hygiene as well as limiting social gatherings can also help to achieve a significant reduction in transmission, said Prof Teo.