Editor’s note: This series is produced in collaboration with the World Health Organization (WHO).

With the winter season in the northern hemisphere, the cold weather conditions force people to stay indoors. In connection with children returning to school and reopening their offices, there is concern about a second wave of coronavirus in Europe, North America and other parts of the world.

COVID-19 is a highly contagious respiratory disease. In closed and crowded indoor spaces, there is a higher risk of spreading than outdoors, where the flow of fresh air can dilute and disperse the virus particles.

According to the WHO, the coronavirus is mainly transmitted through droplets that spread through direct or close contact with an infected person and indirect contact with contaminated surfaces, also known as fomite transmission.

However, there is also the possibility of airborne transmission in crowded indoor spaces with poor ventilation such as restaurants, gyms, nightclubs, and offices.

A number of measures can be taken in such closed environments to reduce the risk of infection.

Natural ventilation

Ventilation is the introduction of fresh air into an interior space while the stale air is pushed outside.

Whether at home or in public buildings such as schools and offices, ventilation can be improved by simply opening windows and doors whenever possible.

Luca Fontana, a Water, Hygiene and Hygiene (WASH) adviser to WHO, said Al Jazeera’s ventilation was “part of the big package of measures to prevent and fight infection,” along with physical distancing, hand hygiene and face masks .

“The general suggestion for building ventilation is to provide healthy air to breathe, by both diluting the pollutant from the building and removing the pollutant from the room itself,” he said in a recent live Q&A on Facebook.

HVAC systems

In public spaces, ventilation through mechanical measures such as heating, ventilation and air conditioning systems can help improve the quality of the indoor air.

According to the WHO, a well-maintained and operated HVAC system can reduce the spread of COVID-19 indoors by increasing the air exchange rate, decreasing air circulation and increasing the use of outside air.

The air should preferably not be recirculated, and the HVAC systems should be regularly checked, maintained, and cleaned by professionals.

The WHO has set technical specifications for the operation and maintenance of these systems as part of COVID-19.

Air blown directly from one infected person to another in an enclosed space can increase the transmission of the virus from one person to another.

Maria Neira, WHO

Filters and fans

Highly efficient particulate filters (HEPA), commonly used in airplanes and hospitals, are another useful tool for removing viruses and germs from the atmosphere.

These can minimize the length of time exposure to potentially infectious materials caused by coughing or sneezing.

HEPA filters, commonly used in aircraft, can filter up to 99 percent of the particles in the air [File: Kai Pfaffenbach/Reuters]
The use of fans can in certain ways improve air circulation and reduce stagnant air bubbles in an enclosed space.

“A desk or pedestal fan is safe for air circulation among family members living together who are not infected with the virus that causes COVID-19,” said Maria Neira, director of public health and the environment at WHO.

“Fans should be avoided, however, when people who are not part of the immediate family [are present]as some people could have the virus even though they don’t have symptoms, ”she added.

“Air blown directly from one infected person to another in an enclosed space can increase the transmission of the virus from one person to another.”

When using a ceiling fan, Fontana said it was important to maintain good ventilation – for example by opening a window – in order to efficiently improve the exchange of air between inside and outside.

UV lighting

Ultraviolet (UV) radiation can generally be used to disinfect air, water and surfaces. However, its effectiveness in inactivating the SARS-CoV-2 virus that causes COVID-19 is not fully established.

According to the US Food and Drug Administration (FDA), UV radiation has been shown to destroy the outer protein coating of the SARS coronavirus. However, there is limited published data on the wavelength, dose, and duration of UV radiation required for rendering to be inactive.

According to WHO Fontana, UV lamps should always be used with HEPA filters and not as a stand-alone solution.

In the meantime, the UN Department of Health has issued an urgent warning against using UV light to disinfect hands or other areas of skin, as this can cause skin irritation and eye damage.

[Photo courtesy: WHO]

Redesign buildings

The pandemic is also pushing architects, engineers and urban planners to rethink the design of buildings, especially public spaces.

On its website, the US Environmental Protection Agency (EPA) recommends, “Reorienting neighboring workplaces so that employees don’t face each other could be an important part of an overall plan to fight the virus.”

In places like Mauritius, Italy, and Ghana, intensive care units (ICUs) and COVID-19 screening facilities have been purposely built to allow natural ventilation.

“In … the future, defining a clean design could strengthen the use of natural ventilation in various healthcare settings,” said Fontana, adding that WHO was working to identify key design criteria not only for COVID-19 but other potential respiratory diseases as well .

Check air quality

Simple devices are available on the market with which the air volume and direction can be measured.

Measuring the carbon dioxide (CO2) content is a good indicator of indoor air quality, explained Fontana.

“The more crowded the place is, the more CO2 is produced in the room. and the more effective the ventilation, the lower the CO2 levels, ”he said.

Companies are also looking for more sophisticated and innovative ways to fight the pandemic.

PathogenDx, a US-based company, has developed a DNA / RNA-based microarray test technology to specifically detect the new coronavirus in the air and on surfaces.

Human specimen diagnosis has yet to be approved by the FDA, but the company is already selling its kits for environmental testing.

Milan Patel, co-founder and CEO of PathogenDx, told Al Jazeera this hybrid technology could be beneficial in airplanes, gyms, call centers and other enclosed spaces.

The Cherokee Native American Nation is one of their largest customers, performing 200 to 300 tests on their population every month.

“This is not a home test. It’s one that a lab does because it’s ultimately a molecular type of test and all of the lab equipment is needed … and the sensitivity of that type of equipment, ”said Patel.

Follow Saba Aziz on Twitter: @saba_aziz


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