Ventilation is key to controlling Covid

We need a national project to improve the air we breathe in buildings and vehicles

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Making sure windows are open on public transport is a vital way to reduce the risk of the spread of infectious diseases like Covid and tuberculosis. Photo: Ashraf Hendricks

Though vaccines seem less effective against the Omicron variant of Covid, they still protect us from serious harm and everyone should get vaccinated. But vaccination is not enough. A multi-layered strategy, including ventilation of indoor spaces, will reduce transmission and is urgently needed.

If we can reduce the average number of people that each person with Covid infects to less than one for just a few weeks, we can stop the epidemic. We have the tools to do this.

By now, we know the coronavirus is airborne. This means that small particles emitted by infected people when they breathe transmit the virus both up close and at distances greater than one metre. We also know transmission is rare from contaminated surfaces.

Effective ways to prevent transmission, therefore, are to wear a high quality, well-fitted mask over your nose and mouth, and to remove the contaminated air. In other words, improve the ventilation of indoor spaces where viruses in aerosols accumulate. Ventilation means removing indoor stale air and bringing outdoor fresh air into the room.

Mask wearing in indoor spaces is essential and effective, but relies on constant adherence to a prescribed behaviour that many people are uncomfortable with. There is, at last, more public messaging and awareness of the importance of ventilation as the additional key intervention. “Open the windows and doors” is good advice. This still relies on human behaviour, but improves ventilation and is less onerous than mask wearing.

Sometimes it’s obvious a space is poorly ventilated – a crowded and stuffy bar or tavern, an interior office with no windows, a fully occupied taxi with windows all shut. In other cases, it’s less clear. Air conditioners may recirculate the contaminated air, cooling it for thermal comfort but not cleaning or dispersing it, while creating the illusion of freshness. In larger, newer buildings, windows may not open, but mechanical ventilation systems, which form part of a building’s structure, can be very effective.

Ventilation is about the flow of air from high pressure to low. No pressure difference, no flow. Natural ventilation can be excellent, but somewhat unreliable, as there is not always an outdoor breeze, or pressure difference, to generate flow. Open windows may not be enough unless they are on opposite sides of a room, and big enough. Otherwise sufficient air exchange, replacing stale re-breathed air with fresh air, may not occur.

In the context of ventilation, occupancy and activity are key factors. Two people sitting apart quietly in a large, poorly ventilated space is much less risky than 20 loud, unmasked friends socialising over a meal in the same space. So reduced occupancy often makes sense, but only in relation to the actual amount of ventilation in the room, people’s activity and the wearing of masks.

Banning outdoor stadium events is less sensible. Outdoors, there’s still the chance of being infected by a person right next to you breathing or coughing directly in your face, but little chance of super-spreading, where the virus is transmitted to many other people at a distance. Super-spreading is very important. No super-spreading, no pandemic. But super-spreading occurs only in enclosed occupied spaces like restaurants, offices, buses or taxis.

A hundred years ago, during the Spanish flu pandemic, the city of Chicago formed an army of inspectors to examine all buildings to ensure they were well ventilated based on clear standards and measurement. Landlords were ordered to install and pay the running costs of heating so that windows could be open during the harsh winter. Chicago avoided the large second wave that other US cities experienced.

We need our own project focused on checking and improving the air quality of all occupied indoor spaces so that Covid and other respiratory diseases are no longer spread. Project Umoya (Xhosa for air) could be our Chicago project. In Project Umoya, all buildings, especially larger ones with mechanical ventilation systems, would be inspected and owners required to make them safe for occupancy during the pandemic, or made off limits if that is impossible.

The inspection of office buildings, factory floors, classrooms, restaurants, malls, and auditoriums, by experts, and an army of people they could train and deploy, would reveal whether ventilation systems are actually turned “on”. When was the last maintenance? Are fresh air intakes on the outside of the building open? Are systems set to “automatic” so they only come on when the temperature changes? Are the various indoor grilles and vents for extraction and inflow open, or rusted shut? Are filters in place or clogged? What is the measured flow of fresh air? Ventilation depends on the size of the space and its occupancy, both easy to measure, while other aspects of ventilation require more expertise to assess.

Standards exist for ventilation but until now have been focused not on health but comfort, for example reducing levels of “bio-effluents” - that is, body odour (!) - which make indoor spaces unpleasant. A fresh air flow of at least ten litres per person per second is now accepted as required to reduce contamination of the air with viruses (such as SARS-COV-2) bacteria (such as TB) and other harmful contaminants. This is much higher than the current South African building standards which desperately need revision.

Measurement can tell us the maximum number of people that can be safely accommodated in an indoor space. Carbon dioxide levels show how much rebreathed air is in a room or vehicle.

Taxis, trains and buses can be fitted with simple mechanisms to keep windows open. Vehicle air conditioners can be set to fresh air mode.

In Project Umoya, each building and vehicle would be certified and this certification will be visible to the public. The GreenFlag Association has developed an accreditation system for this purpose.

South Africa is fortunate to have a mild climate. We can use natural ventilation to make indoor spaces safer and healthier, but we also need to ensure our buildings’ mechanical ventilation systems are working properly and that people working, learning, playing and living in them know they are protected from Covid and other infectious diseases. This effort will deliver a large return on investment, in both health and restored economic activity. A concerted national effort to improve the air we breathe in buildings and vehicles is therefore worthwhile.

Kantor is with the University of Cape Town, Insight Actuaries and Consultants, and Institute for Healthcare Improvement. Khoza, Hunter and Chester are with the GreenFlag Association.

Views expressed are not necessarily GroundUp’s.

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TOPICS:  Covid-19

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