5 tips for ventilation to reduce COVID risk at home and work



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Mary-Louise McLaws, UNSW

As many of us return to the office, and congregate indoors over dinner and drinks during the summer holidays, we need to think about ventilation to minimise the indoor spread of COVID-19.

SARS-CoV-2, the virus that causes COVID, is spread mostly by larger particles called droplets, but also by smaller particles called aerosols, and by touch from contaminated surfaces.

Aerosol particles are lighter than droplet-sized particles, and can be suspended in the air for longer. The suspension and therefore transmission of aerosols is facilitated by poor ventilation.

Increasing ventilation indoors, with fresh outdoor air, is a key method of dispersing viral particles. Ventilation can reduce the risk that just one COVID-positive person (who might not yet know they’re infectious) will infect others.

There are some simple measures you can take, both at home and at work, to improve ventilation over the holiday period and beyond.




Read more:
Poor ventilation may be adding to nursing homes’ COVID-19 risks


1. Open windows and doors

The best strategy at home and at work is simply to open windows and doors.

If you’re having friends and family over for a meal, or your office Christmas party, consider moving tables and chairs closer to open windows and open up a door to create a through breeze.

Or, if weather permits, eat outside.

2. Set your air conditioner to pull fresh air from outside

Air conditioners can help, but they must be on the right setting.

At work or home you don’t want to recirculate indoor air, as this just fans the same air around the room (but now colder or warmer).

Instead, always make sure your air conditioner is set to bring in 100% fresh air from outside. There are settings in offices that allow the system to increase air change per hour, meaning it can reduce the time it takes for all the air inside the room to be completely replaced with outside fresh air.

A person using a remote for their air conditioner
Aircons can help ventilate rooms, but only if they’re inserting fresh air from outside, rather than recirculating indoor air.
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But the direction of the airflow is also important. For example, airflow from an air conditioner (that was recirculating air rather than pulling it from outside) was implicated in spreading the virus to a number of diners at tables downstream in a restaurant in China.

Offices welcoming back staff should prepare their air conditioners by having their engineers service the system to pull in fresh air faster than the pre-COVID setting (which may have been around 40 litres per second per person) at no less than 60 litres per second, per person.

In hospitals, aged-care facilities and hotel quarantine, qualified engineers should be brought in to assess the adequacy of the air conditioner’s airflow. This is particularly crucial for any “hot zones” accommodating people who are COVID-positive.

The World Health Organisation recommends hot zones have 12 airflow changes per hour (that’s 80 litres per second per person), meaning the air is totally replaced 12 times every 60 minutes. This is the gold standard for ventilation, and can be very hard to achieve in many buildings.




Read more:
Many of our buildings are poorly ventilated, and that adds to COVID risks


3. Use fans

Guidelines released last week by the US Centers for Disease Control and Prevention recommend placing fans near open windows to enhance airflow. The recommendation is to keep fans on at all times when a room is occupied, for example at restaurants.

As with aircons, fans can be dangerous if they push the air directly from one person to another, and one is infectious. You should place the fan so it increases the flow of fresh air into the room, and shouldn’t be placed so the air moves from the room towards the open window or open door.

4. Don’t bother with HEPA filters at home

High-efficiency particulate air (HEPA) filters have been marketed as a way to reduce the concentration of SARS-CoV-2 particles in the air.

Their effectiveness is dependent on the airflow capacity of the unit, the configuration of the room, the number of people in the room, and the position of the filter in the room.

But there’s no evidence to suggest a portable HEPA filter unit will help in your home. So don’t rush out and buy one for Christmas.

They may be effective in some areas of health care, such as a COVID ward in a hospital or in aged care homes, particularly when used in negative-pressure rooms. The combination of the HEPA filter and negative air pressure reduces the risk of aerosol particles escaping into the corridor.

5. In public transport, taxis and Ubers

COVID outbreaks have been traced back to exposure on public transport. For example, a young man in Hunan Province, China, travelled on two buses and infected multiple people who were sitting in different areas of the buses. A study of this cluster was carried out by Chinese researchers, who put forward one theory regarding air flow:

The closed windows with running ventilation on the buses could have created an ideal environment for aerosol transmission […] the ventilation inlets were aligned above the windows on both sides, and the exhaust fan was in the front, possibly creating an airflow carrying aerosols containing the viral particles from the rear to the middle and front of the vehicle.

The study’s authors recommend all windows be open on public transport to help disperse viral particles. If you’re on a tram or a bus, you should open them if you can.

However, on some forms of public transport it might be impossible, like trains. In these instances, you should wear a mask.

Likewise, it’s ideal to have the windows down in Ubers and taxis. But if you can’t or don’t want to, turn on the air conditioner and have it pull fresh air from outside. And still wear a mask!The Conversation

Mary-Louise McLaws, Professor of Epidemiology Healthcare Infection and Infectious Diseases Control, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Many of our buildings are poorly ventilated, and that adds to COVID risks



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Geoff Hanmer and Bruce Milthorpe, University of Technology Sydney

The virus that causes COVID-19 is much more likely to spread indoors rather than outdoors. Governments are right to encourage more outdoor dining and drinking, but it is important they also do everything they can to make indoor venues as safe as possible. Our recent monitoring of public buildings has shown many have poor ventilation.

Poor ventilation raises the risks of super-spreader events. The risk of catching COVID-19 indoors is 18.7 times higher than in the open air, according to the US Centers for Disease Control and Prevention.




Read more:
Poor ventilation may be adding to nursing homes’ COVID-19 risks


In the past month, we have measured air quality in a large number of public buildings. High carbon dioxide (CO₂) levels indicate poor ventilation. Multiple restaurants, two hotels, two major shopping centres, several university buildings, a pharmacy and a GP consulting suite had CO₂ levels well above best practice and also above the absolute maximum mandated in the National Construction Code.

Relative humidity readings of less than 40% associated with both heating and cooling air are also of concern. Evidence now suggests low humidity is associated with transmission.

If anyone had COVID-19 in these environments, particularly if people were in them for an extended period, as might happen at a restaurant or pub, there would be a risk of a super-spreader event. Less than 20% of individuals produce over 80% of infections.




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Many aged-care deaths were connected

It appears a relatively small number of super-spreader events, probably associated with airborne transmission of SARS-CoV-2, the virus that causes COVID-19, were responsible for most of the deaths in Victorian aged-care facilities.

Of the 907 people who have died of COVID-19 in Australia, 746, or 82% of COVID-19 deaths, were associated with aged care. In Victoria, there were 52 facilities with more than 20 infections. Three had over 200 infections. As a result, 639 of the 646 aged care residents who died in Victoria were located in just 52 facilities.

But official advice hasn’t changed

Aged-care operators and the states based their infection control on the advice of the Commonwealth Infection Control Expert Group (ICEG). As of September 6, the Coronavirus (COVID-19) Residential Aged Care Facilities Plan for Victoria stated:

Coronavirus (COVID-19) is transmitted via droplets, after exposure to contaminated surfaces or after close contact with an infected person (without using appropriate PPE). Airborne spread has not been reported [our emphasis] but could occur during certain aerosol-generating procedures (medical procedures which are not usually conducted in RACF). […] Respiratory hygiene and cough etiquette, hand hygiene and regular cleaning of surfaces are paramount to preventing transmission.

In early August, more than 3,000 health workers had signed a letter of no confidence in ICEG. The letter noted that aerosol transmission was causing infections in medical staff, many of whom worked in aged-care facilities.

On September 7, we wrote to the federal aged care minister, Richard Colbeck, drawing attention to our August 20 article in The Conversation, which referenced a July 8 article in Nature. The Nature article identified an emerging consensus that aerosol transmission of SARS-CoV-2 is probable in low-ventilation environments.




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How to prevent COVID-19 ‘superspreader’ events indoors this winter


The director of the Aged Care COVID-19 Measures Implementation Branch wrote back on Colbeck’s behalf on September 28 saying:

Current evidence suggests COVID-19 most commonly spreads from close contact with someone who is infectious. It can also spread from touching a surface that has recently been contaminated with the respiratory droplets (cough or sneeze) of an infected person and then touching your eyes, nose or mouth.

In other words, Commonwealth authorities were still playing down the significance of airborne transmission nearly two months after the letter of no confidence was sent to ICEG and three months after the article in Nature. By the end of September, Victorian aged-care facilities had reported over 4,000 cases of COVID-19, about half of them in staff.

On October 23, ICEG was still saying:

There is little clinical or epidemiological evidence of significant transmission of SARS-CoV-2 (the virus that causes COVID-19) by aerosols.

Focus on the ‘3 Vs’ to reduce risks

The key thing we need to do until a vaccine is rolled out is to try to prevent indoor super-spreader events. According to the University of Nebraska Medical Centre, we should remember the “three Vs” that super-spreader events have in common:

Venue: multiple people indoors, where social distancing is often harder

Ventilation: staying in one place with limited fresh air

Vocalization: lots of talking, yelling or singing, which can aerosolize the virus.

Measuring indoor ventilation is quick and easy using a carbon dioxide detector. Any CO₂ reading of over 800 parts per million is a cause for concern – the level for air outside is just over 400ppm.

There is no excuse for governments, health authorities and building owners not to monitor ventilation levels to help ensure members of the public are as safe as is reasonably practicable when indoors.

There is also no excuse for the Australian Building Control Board not to change the National Construction Code to require fall-back mechanical ventilation systems be fitted and CO₂ and humidity monitored in all buildings frequented by the public, particularly aged-care facilities.

With the knowledge we have now and a low rate of community infection, Australia should be able to make it through to vaccine roll-out with relatively few further infections and deaths. But that depends on being vigilant about the quality of ventilation indoors and the associated possibility of super-spreader events. This is especially important in aged-care facilities and quarantine hotels.

It’s probably a good idea for us all to open the windows and let the fresh air in.The Conversation

Geoff Hanmer, Adjunct Professor of Architecture and Bruce Milthorpe, Emeritus Professor, Faculty of Science, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Poor ventilation may be adding to nursing homes’ COVID-19 risks


Geoff Hanmer and Bruce Milthorpe, University of Technology Sydney

Over 2,000 active cases of COVID-19 and 245 resident deaths as of August 19 have been linked to aged care homes in Victoria, spread across over 120 facilities. The St Basil’s cluster alone now involves 191 cases. In New South Wales, 37 residents were infected at Newmarch House, leading to 17 deaths.

Why are so many aged care residents and staff becoming infected with COVID-19? New research suggests poor ventilation may be one of the factors. RMIT researchers are finding levels of carbon dioxide in some nursing homes that are more than three times the recommended level, which points to poor ventilation.

An examination of the design of Newmarch in Sydney and St Basil’s in Melbourne shows residents’ rooms are arranged on both sides of a wide central corridor.

The corridors need to be wide enough for beds to be wheeled in and out of rooms, but this means they enclose a large volume of air. Windows in the residents’ rooms only indirectly ventilate this large interior space. In addition, the wide corridors encourage socialising.

If the windows to residents’ rooms are shut or nearly shut in winter, these buildings are likely to have very low levels of ventilation, which may contribute to the spread of COVID-19. If anyone in the building is infected, the risk of cross-infection may be significant even if personal protective equipment protocols are followed and surfaces are cleaned regularly.

Why does ventilation matter?

Scientists now suspect the virus that causes COVID-19 can be transmitted as an aerosol as well as by droplets. Airborne transmission means poor ventilation is likely to contribute to infections.

A recent article in the journal Nature outlines the state of research:

Converging lines of evidence indicate that SARS-CoV-2, the coronavirus responsible for the COVID-19 pandemic, can pass from person to person in tiny droplets called aerosols that waft through the air and accumulate over time. After months of debate about whether people can transmit the virus through exhaled air, there is growing concern among scientists about this transmission route.




Read more:
Is the airborne route a major source of coronavirus transmission?


Under the National Construction Code (NCC), a building can be either “naturally ventilated” or “mechanically ventilated”.

Natural ventilation requires only that ventilation openings, usually the openable portion of windows, must achieve a set percentage of the floor area. It does not require windows to be open, or even mandate the minimum openable area, or any other measures that would ensure effective ventilation. Air quality tests are not required before or after occupation for a naturally ventilated building.

Nearly all aged care homes are designed to be naturally ventilated with openable windows to each room. In winter most windows are shut to keep residents warm and reduce drafts. This reduces heating costs, so operators have a possible incentive to keep ventilation rates down.

From inspection, many areas of typical nursing homes, including corridors and large common spaces, are not directly ventilated or are very poorly ventilated. The odour sometimes associated with nursing homes, which is a concern for residents and their visitors, is probably linked to poor ventilation.

Carbon dioxide levels sound a warning

Carbon dioxide levels in a building are a close proxy for the effectiveness of ventilation because people breathe out CO₂. The National Construction Code mandates CO₂ levels of less than 850 parts per million (ppm) in the air inside a building averaged over eight hours. A well-ventilated room will be 800ppm or less – 600ppm is regarded as a best practice target. Outside air is just over 400ppm

An RMIT team led by Professor Priya Rajagopalan is researching air quality in Victorian aged care homes. He has provided preliminary data showing peaks of up to 2,000ppm in common areas of some aged care homes.

This figure indicates very poor ventilation. It’s more than twice the maximum permitted by the building code and more than three times the level of best practice.

Research from Europe also indicates ventilation in aged care homes is poor.

Good ventilation has been associated with reduced transmission of pathogens. In 2019, researchers in Taiwan linked a tuberculosis outbreak at a Taipei University with internal CO₂ levels of 3,000ppm. Improving ventilation to reduce CO₂ to 600ppm stopped the outbreak.




Read more:
How to use ventilation and air filtration to prevent the spread of coronavirus indoors


What can homes do to improve ventilation?

Nursing home operators can take simple steps to achieve adequate ventilation. An air quality detector that can reliably measure CO₂ levels costs about A$200.

If levels in an area are significantly above 600ppm over five to ten minutes, there would be a strong case to improve ventilation. At levels over 1,000ppm the need to improve ventilation would be urgent.

Most nursing homes are heated by reverse-cycle split-system air conditioners or warm air heating systems. The vast majority of these units do not introduce fresh air into the spaces they serve.

The first step should be to open windows as much as possible – even though this may make maintaining a comfortable temperature more difficult.




Read more:
Open windows to help stop the spread of coronavirus, advises architectural engineer


Creating a flow of warmed and filtered fresh air from central corridor spaces into rooms and out through windows would be ideal, but would probably require investment in mechanical ventilation.

Temporary solutions could include:

  1. industrial heating fans and flexible ventilation duct from an open window discharging into the central corridor spaces

  2. radiant heaters in rooms, instead of recirculating heat pump air conditioners, and windows opened far enough to lower CO₂ levels consistently below 850ppm in rooms and corridors.

The same type of advice applies to any naturally ventilated buildings, including schools, restaurants, pubs, clubs and small shops. The operators of these venues should ensure ventilation is good and be aware that many air-conditioning and heating units do not introduce fresh air.

People walking into venues might want to turn around and walk out if their nose tells them ventilation is inadequate. We have a highly developed sense of smell for many reasons, and avoiding badly ventilated spaces is one of them.The Conversation

Geoff Hanmer, Adjunct Professor of Architecture and Bruce Milthorpe, Emeritus Professor, Faculty of Science, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.