Masks, ventilation, vaccination: 3 ways to protect our kids against the Delta variant


Shutterstock

Katrina McLean, Bond University and Natasha Yates, Bond UniversityLast year in the COVID-19 pandemic, children were not catching or spreading the virus much. The main focus was on protecting our elderly and vulnerable.

But the Delta strain has changed things. Children around the world are contracting Delta in high numbers and some frontline doctors believe they may also be getting sicker from this strain.

Many parents and schools have concerns about how to best protect children from COVID-19. There’s also the worry children will catch the virus at school and take it back to their families and communities.

While many children are now well-accustomed to washing and sanitising their hands, this is simply not enough to tackle the spread of COVID-19, especially now we know the virus is airborne. We need a whole toolbox of strategies.

There are three key areas to focus on that we believe are evidence-based, easy to implement and will help protect our children: masks, ventilation and vaccination.

1. Masks

In certain Australian states, children aged 12 and above are currently required to wear a mask in public areas (schools included).

Meanwhile, Victoria’s chief health officer Brett Sutton has recommended children aged five and up wear masks in the face of rising Delta transmission among children.

As GPs, parents often ask us if it’s safe for children to wear masks. While we understand concern from parents, we reassure them masks have been found to cause no harm in children over the age of two. When children wear masks it doesn’t affect their breathing or reduce their oxygen levels.

Importantly, when worn properly, masks are effective at reducing the spread of COVID-19, for adults and children alike.




Read more:
Under-12s are increasingly catching COVID-19. How sick are they getting and when will we be able to vaccinate them?


A few quick tips. Fabric masks should be treated like underwear: wash them regularly, ensure they cover everything, and don’t share. These are a better option for the environment.

Label fabric masks like school hats — they will go missing!

Surgical/disposable masks are single use. Like using a tissue to blow your nose, make sure it goes in the bin once used and then wash your hands.

And masks should fit snugly — the less gaps there are the better they will work.



Like anything new, getting used to masks can take time. Children may initially be anxious, especially if their parents are too. Though most kids adapt really quickly (much quicker than adults, in our experience).

While the majority of children will adapt quickly there will be some who have specific and legitimate concerns, for example disabilities and sensory issues. GPs and paediatricians can help work out what the safest approach is for these children.

2. Ventilation

SARS-CoV-2, the virus that causes COVID-19, can float in the air like smoke. If you’re inside in a small enclosed room with other people and the ventilation is poor, it will only be a matter of time before you’re all breathing in each other’s air.

Schools have lots of children inside enclosed classrooms, often for hours, so what can be done?

Ventilation is something schools can and should address. Some simple strategies include:

  • get outside as often as is practical. Call children into the classroom only once the day has started. Hold some lessons outside the classroom. During breaks and lunch time children should be outside whenever possible too
  • open doors and windows
  • set air conditioning or heating systems to bring in as much outdoor air as possible
  • check the air with carbon dioxide monitors. This is occurring overseas.

Why do we care about CO₂? Well, we breathe in oxygen and breathe out CO₂. In confined spaces with lots of air that has been “breathed out”, monitors will detect higher levels of CO₂.

All that “breathed out” air could be full of viral particles, so if the monitor is measuring high, airflow needs to be improved immediately by opening a door or window.

In stuffy rooms, or rooms that measure high for CO₂ (indicating the ventilation is poor), a longer-term plan to clean the air should be considered. What’s encouraging is that the technology already exists to address this.

Air cleaners, also known as air purifiers, scrubbers, or HEPA filters, can actually help to “clean” the air we breathe. Lots of schools around the world are now actively improving ventilation systems and air quality monitoring.

Improving the air quality in schools may also prevent some of the other colds and flus kids pick up at school, and reduce asthma and allergy symptoms.

3. Vaccination

At this stage in Australia the Pfizer vaccine is recommended for vulnerable children aged 12-15, including those registered on the National Disability Insurance Scheme.

Vaccinations for all children 12 and over are now under way in New Zealand.

New Zealand GP Dr Sarah Hortop shared this photo of her daughters who received their first dose of the Pfizer vaccine recently.
Sarah Hortop, Author provided

Many other countries have been giving vaccines to children for several months now. For example, in the United States, more than one-third of 12 to 15-year-olds are fully vaccinated and nearly 50% have had at least one dose.

We know the vaccines work well in this age group and just like in adults, there is very close monitoring of adverse events from these vaccines in children. It’s reassuring to see very few serious reactions, and even those that are (for example myocarditis — inflammation of the heart) are treatable.

Vaccine trials are under way in children under 12 in the US (for Pfizer and Moderna), and once we have the safety and efficacy data we can start making decisions around vaccinating them too.




Read more:
We should install air purifiers with HEPA filters in every classroom. It could help with COVID, bushfire smoke and asthma


The Conversation


Katrina McLean, Assistant Professor, Medicine, Bond University and Natasha Yates, Assistant Professor, General Practice, Bond University

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

Poorly ventilated schools are a super-spreader event waiting to happen. It may be as simple as opening windows


Shutterstock

Geoff Hanmer, University of Technology Sydney and Bruce Milthorpe, University of Technology SydneyInfections of the Deltra strain are increasing across Australia. A significant number of recent outbreaks have been in schools.

In the earlier waves of the COVID outbreak, in 2020, evidence showed children were getting COVID at much lower rates than adults, and the advice from experts was to keep schools open. But a series of papers later showed children were at similar risk of infection to adults.

This is even worse with Delta. According to the US Centers for Disease Control, the Delta variant is about twice as infectious as the earlier strains. And preliminary data suggest children and adolescents are at greater risk of becoming infected with this variant, and transmitting it.




Read more:
Is it more infectious? Is it spreading in schools? This is what we know about the Delta variant and kids


The World Health Organization has recognised SARS-CoV-2, the virus that causes COVID-19, is airborne. The evidence for aerosol transmission is now enough for the Australian Infection Control Expert Group (ICEG), which advises the federal government, to have recently amended its earlier advice that COVID-19 was only spread by contact and droplets:

ICEG has also recognised broader circumstances in which there may be potential for aerosol transmission […] ICEG […] notes the risk may be higher under certain conditions, such as poorly ventilated indoor crowded environments.

“Poorly ventilated indoor crowded environments” accurately describes conditions at many schools. Even in lockdown, schools are still open for children of essential workers and classrooms in use can have relatively high occupancy.

In or out of lockdown, poorly ventilated schools are a super-spreader event waiting to happen.

How are schools ventilated?

Most schools are naturally ventilated. This means windows must be open to deliver fresh air which will dilute and disperse airborne pathogens.

It is not a coincidence the current Australian outbreaks are happening in winter, when naturally ventilated buildings, including most schools, are more likely to have their windows shut to keep the heat in.

Some schools, particularly those with open learning spaces, have buildings too deep for natural ventilation and are mechanically ventilated. This may involve air conditioning, but not all air conditioning includes ventilation. For instance, a split system air conditioner typically recirculates air inside a space whereas ventilation introduces fresh air into the building.




Read more:
The pressure is on for Australia to accept the coronavirus really can spread in the air we breathe


Mechanically ventilated buildings are supposed to have around 10 litres per second (l/s) of fresh air per person. But the temptation to throttle back fresh air to save energy and money is ever present. And even with 10 l/s per person coming in, there may be places with poor ventilation. This includes stairwells, lifts, corridors and assembly spaces.

As aerosols may persist in the air for hours, schools with poor ventilation become a high risk for transmission and kids can take it back to their families.

We have been measuring ventilation in schools and other buildings in Sydney, Canberra, Brisbane and Adelaide using a carbon dioxide (CO2) meter. This is because C02, which is exhaled by humans, is a good proxy for the level of ventilation in a space.

Outside air is about 400-415 ppm (parts per million) of CO2 and well-ventilated indoor environments are typically below 800 ppm with best practice around 600 ppm.

CO₂ monitor in school showing 417ppm
This measurement of a classroom in an older-built school shows safe CO2 levels.
Author provided

Our informal measurements show many newer mechanically ventilated buildings are not well ventilated. Perhaps counter-intuitively, older style naturally ventilated school buildings with leaky wooden windows on both sides of the room and high ceilings often appear to perform well.

Just looking at a building is not a reliable guide to how well ventilated it is.

What schools need to do

We can do several things to ensure schools are well ventilated. The first is to ensure the school has access to a CO2 meter and takes action where CO2 is above 800 ppm.

If the building has windows and doors, open them. This may require kids and teachers putting on an extra layer of clothing, turning up the heating, providing supplementary heaters and making revised security arrangements.

Anything required to keep people safe and thermally comfortable in a well ventilated space is likely to be much cheaper than dealing with an outbreak.

Serviceable standalone NDIR sensor-type CO2 meters can be bought online for less than A$100. More sophisticated networkable devices are available for under A$500.




Read more:
Australian children are learning in classrooms with very poor air quality


If the space is mechanically ventilated, a school will need to get a mechanical engineer to work out how the system can be improved. In the meantime, staff could try opening doors, using fans to mix air in large volume spaces or move activities outside.

Where improvements in ventilation are not immediately possible, portable air purifiers can reduce the amount of virus in the air. An air purifier will need at least a HEPA (high-efficiency particulate absorbing) filter to be effective and has to be matched to the size of the room. A typical classroom may need two devices to work and a large open plan space may need several.

In future, we will need to change building regulations to deliver safe, clean air in schools. For now, we just need to do the best we can. It may be as simple as opening the windows.The Conversation

Geoff Hanmer, Honorary Professional Fellow, University of Technology Sydney 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.

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



Shutterstock

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.
Shutterstock

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



ambimages/Shutterstock

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.




Read more:
A few superspreaders transmit the majority of coronavirus cases


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.




Read more:
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.