Are workplaces safe from airborne Covid-19 transmissions?


KUALA LUMPUR – When was the last time the ventilation and air-conditioning system in your workplace was serviced?

The issue pertaining to the proper maintenance of indoor cooling and ventilation systems has become all the more pertinent now in the wake of international scientific proof that SARS-CoV-2 – that causes COVID-19 – can spread through the air.

In Malaysia, a team of researchers from Universiti Kebangsaan Malaysia (UKM) has carried out studies showing that the killer coronavirus can remain suspended in the air for up to eight hours in enclosed spaces without proper ventilation and can spread as far as six metres in aerosol particles.     

The studies on suspended particles as potential carriers of the COVID-19 virus were led by senior lecturer at UKM’s Department of Earth Science and Environment Associate Prof Dr Mohd Shahrul Mohd Nadzir, whose team comprised virologists Associate Prof Dr Nazlina Ibrahim, Dr Norefrina Shafinaz Md Nor and Dr Yip Chee Wai.

The first study was carried out between April and May 2020 and the second study from August to October 2020.

A report on the findings from their first study was published in the international scientific journal Nature Scientific Reports in January this year.   

“Based on our (second) study, we found that enclosed spaces without any circulation of fresh air and with air-conditioning operations that recycle the same air can facilitate the transmission of the virus in the air via aerosols.

“This is why it is so important for buildings to have a good ventilation system. Houses should have their doors and windows kept open; in the case of offices and factories, their air-conditioning and ventilation system must be maintained regularly,” said Mohd Shahrul. 

He told Bernama the lack of good ventilation and poor maintenance of the air-conditioning system can trigger workplace clusters if any employee is infected by the COVID-19 virus.   


Last month, Health director-general Tan Sri Dr Noor Hisham Abdullah had said that medical publication The Lancet had reported the possibility of COVID-19 being airborne and not just spreading through droplets.

Many COVID-19 clusters linked to the workplace have emerged since the start of the pandemic in January 2020. As of May 26, a total of 1,085 workplace clusters – with a total of 129,322 cases – has been reported in Malaysia.

The trend has been worrying in recent months as 287 workplace clusters, totalling 17,087 cases, were reported between April 1 and May 26. To date, 233 of these clusters are still active, accounting for 16,785 cases.

The risk of airborne transmission of the virus is one of the reasons why employees are advised to wear a face mask while at work.

However, according to Mohd Shahrul, other standard operating procedures (SOP) such as frequent washing of hands and observing physical distancing may not provide adequate protection against the airborne microparticles that carry the virus transmitted by COVID-19 infected individuals.

“Currently (during the full Movement Control Order), only 20 percent of public service staff and 60 percent of private-sector employees are allowed to work at the office but even if they are seated far from each other, there is still a chance of them being infected by the virus if their office is not well ventilated,” he pointed out.


Elaborating on the findings of their studies – which were done in collaboration with Universiti Tunku Abdul Rahman indoor air simulation expert Associate Prof Dr Bernard Saw Lip Huat and Universiti Malaya toxicologist Dr Leo Bey Fen – Mohd Shahrul said the COVID-19 virus can remain in the air for several hours, which makes it more difficult to control transmissions, more so in buildings that have poorly maintained air-conditioning and ventilation systems.    

In such enclosed spaces, droplets released via coughing, sneezing or talking by a COVID-19 positive person can get caught in the tiny suspended one-micrometre-sized air particles.

(When a person breathes, talks, coughs or sneezes, droplets of various sizes are released. While the larger droplets of up to 10 micrometres fall to the ground, the finer ones can remain suspended in the air.)

The worrying part is, the researchers found that the much smaller COVID-19 virus, which is between 65 and 125 nanometres in size, can remain in the air for more than eight hours if there is no change in the airflow.              Saw, meanwhile, said their second study was conducted in a closed hospital ward with a COVID-19 positive patient. This ward used cassette air-conditioning units that could only recirculate the air within the enclosed space, with no air flowing in from outside.

“Based on our study using computational fluid dynamics, we found that the SARS-CoV-2 virus did not go outside the ward concerned.

“It remained suspended in the air in the ward because there was no flow of fresh air to cleanse the virus,” he explained.

The study found that about 50 percent of the virus in the ward spread within a diameter of one metre while the remaining half spread to over two metres up to six metres to the end of the ward.


In view of the findings of Malaysian and international scientists on the potential danger posed by the airborne COVID-19 virus and with the highly transmissible variants from India, South Africa, United Kingdom and Nigeria having been detected in Malaysia, it is imperative that employers pay attention to their indoor air quality.

“There is no other way. Employers must take into account the importance of indoor air quality,” said Saw, adding that since most employers use centralised air-conditioners, they must also put in place a system that allows fresh air to flow into the building at regular intervals.    

“This is done in China where the air-conditioning system is controlled in such a way that for 30 minutes three times a day, fresh air is allowed into the building to flush out the indoor air. However, not many employers are willing to implement such a system because of the (high) costs involved.”

Saw also pointed out there is no point in sanitising the office without maintaining its air-conditioning system regularly because the risk of transmission will arise again if a COVID-19 infected person comes to work two days after the space has been disinfected.

He also opined that employers can improve their indoor air quality by using air purifiers that possess the HEPA (high-efficiency particulate absorbing) filter. 

“It (air purifier) will not give 100 percent protection but can help to reduce the transmission of the virus in the air.

“The air purifier’s effectiveness also depends on where it is placed. Based on research, it is found to be less effective if placed below the air-conditioner or on the floor. It should ideally be placed at a higher point (in a room),” he added.


On the use of face masks inside buildings, UKM public health specialist Prof Dr Sharifa Ezat Wan Puteh said whether they like it or not, all employees must wear a mask while at work.

However, the type of mask they use can make a big difference when it comes to protecting them against the COVID-19 virus.

Dr Sharifa Ezat said the normal fabric mask can prevent large droplets from being inhaled but not the smaller particles that can penetrate through the fabric.

“The N95 mask or any mask recommended by the Health Ministry is recommended for employees working inside buildings. There are no exceptions because anyone neglecting this (SOP) is exposed to the risk of COVID-19 infection,” she said.

She said it is high time that employers provide a safer working environment for their workforce because “it is not only the risk of COVID-19 infections they are facing but also a host of other health issues related to the Sick Building Syndrome which we have been talking about for a long time”.