While towns along the east coast battle the blazes threatening to devour their homes, Sydney is fighting a different enemy: the pall of smoke that's choking the city.

The air quality is already three times worse than at any moment in the past five years — and it's not showing signs of slowing down.

Cue the familiar jibes about something not being taken seriously until it reaches Sydney. But fire ecologist Professor David Bowman says the city's woes are a sign of the state's bigger problem.

"The classic disaster narrative is disaster, [and then] disaster ends," he says.

"But this [fires] is not behaving like that. This has been going on for six weeks or two months."

We're familiar with the climate-change warnings of heatwaves, bushfire risk and coastal flooding, but this week Sydney has had a reality check about another danger: our air.

The message from authorities is simple: stay indoors and limit your exposure. But while that might work for a day or two, what happens when it becomes the new norm?

According to Dr Lewis, many regions across Australia are already experiencing more frequent fire weather. ( AAP: Darren Pateman )

Cities aren't built for the heat

It's been a shocking reminder as to just how vulnerable the country is to the power of the environment. Hundreds of houses have been lost in these fires alongside swathes of heritage-listed bushland.

While Sydney continues to function, if predictions for how the climate will change in the future bite harder it isn't difficult to imagine catastrophic consequences for urban life across the country.

UNSW Canberra climate scientist Sophie Lewis says our big cities are already being challenged by extreme temperatures — and our infrastructure simply isn't prepared for it.

"When we have heatwaves hit, we know that certain urban infrastructure doesn't cope very well, things like rail lines, transporting large numbers of commuters across Melbourne and Sydney is a real challenge," she says.

"Buildings really trap in that heat and make it difficult for people to escape."

According to the CSIRO's State of the Climate 2018 report, Australia is projected to experience increases in sea and air temperatures, with more hot days and marine heatwaves, and fewer cool extremes.

"Some of the record breaking temperatures we've had over summer in eastern Australia are likely to become mild or average in a few decades time," Dr Lewis says.

"We'll get more frequent heatwaves, but when we do get heatwaves, they'll be more intense."

According to Dr Lewis, many regions across Australia are already experiencing more frequent fire weather with more catastrophic or extreme fire days — and it's something that's projected to continue.

"So we really have to be preparing now for more fires in more locations to be occurring throughout the year," she says.

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"That's going to have consequences not just on those in rural or regional areas who are directly affected by the fires, but in terms of things like air quality and smoke pollution and how that affects things like respiratory illness and asthmatics."

Smoke comes with a healthcare cost

Prepare to get used to hearing the acronym AQI — air quality index.

Along with the danger to lives and homes, there's a mortality rate associated with the poor AQUI due to the subsequent smoke haze — and Professor Bowman says we need to be taking it more seriously now and into the future.

"People will have died and more will die from the air pollution. It's extremely serious," he says.

"There's a pretty significant strata of people who are going to be flooding hospitals with respiratory and cardiovascular disease, and that has a pretty big price tag

"There's a misapprehension among healthy people that the smoke is a nuisance, but that's not true. It's a threat if you're a baby or pregnant or elderly."

Otherwise healthy people aren't immune from the impacts. Sotiris Vardoulakis, a professor of global environmental health at the ANU National Centre for Epidemiology and Population Health, says a sore throat and nose are the most common complaints.

"And potentially some difficulty breathing, but these symptoms are typically reversible and go away once air quality levels return to normal," he says.

"When air pollution is visible you might expect to have some psychological impacts as well, people looking at the haze and feeling sick because of that.

"But having visual impacts, having the smell of air pollution, that can help us realise we're exposed and take some precautionary measures."

Prepare to accept masks as fashion

They're hard to find on Sydney's shelves, but ask someone where they got their high-quality mask in Sydney this week, and you'll keep hearing the same muffled answer: China.

Tactics to survive in smog and smoke have become part of everyday life in a country that has battled what is wryly termed the airpocalypse, or airmageddon, for years.

The health effects of bad air have encouraged a booming industry in consumer items designed to minimise the impact of air pollution.

For residents of Beijing, first on the anti-pollution must-have list is a face mask to wear outdoors that can filter the most dangerous air pollution particles.

The key here is that the mask must be rated to filter at least 95 per cent of the tiny particulate matter known as PM2.5. These pollution particles are just 2.5 micrometres or less in diameter, 20 times smaller than a human hair. They are most dangerous because they are capable of crossing into the bloodstream.

Lise Floris and her husband Francesco moved from Europe to Beijing with their three children in December 2015.

"When we first arrived in Beijing, we hadn't even stepped off the plane before we had our masks on," Floris says. "We landed on a day where the AQI was 300 and we did take it very seriously in the beginning. We decided that the kids had for wear masks as soon as the AQI was over 100."

A woman wears a Mehow pollution mask ( MeHow )

Dozens of international retailers now offer air pollution masks — from disposable versions that leave you looking like you've just stepped out of surgery — to an embroidered and jewel-encrusted fashion statement from MeHow.

For an item that is worn so prominently on the face it is no surprise that "smog chic" is now big business.

International brands like VogMask markets itself just like fashion clothing brands, complete with top-end ad campaigns and fashion parades to launch their seasonal mask ranges that trade on fun, colourful designs. They also have a range for children and toddlers.

These masks are no good if you are a jogger or like exercising outdoors. In that case brands like Respro and Totobobo, offering a tighter seal that won't move during high impact sport, have you covered.

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Beware the outdoors

Across NSW, there have been widespread cancellations of sporting matches and other public events this weekend.

In the next decade, an indoor plan B will become central for planning, not just for barbecues beset by summer storms or total fire bans, but for the danger brought by air quality spikes too.

Professor Vardoulakis says staying indoors is still the best bet of limiting your exposure to the smoke — but that doesn't mean you should become a hermit.

"During long periods of poor air quality, it's important people carry on with their normal lives and exercise as well," he says.

"Of course, when the levels are hazardous we advise people to refrain from strenuous physical exercise outdoors, so exercise indoors, in a gym."

Lise Floris and her husband Francesco wore masks when they first arrived in Beijing. ( Supplied )

But a mask is not always enough to reduce the risks of outdoor exercise and weighing up the risks and benefits of exercise versus exposure to pollution is constantly debated in cities with air pollution problems.

In Beijing, Floris's husband Francesco runs marathons in his spare time and belongs to the running club Hey Running. The club cancels outdoor training sessions when AQI rises above 160 — a figure that Sydney and much of the NSW coast has seen regularly over the past week.

The World Health Organisation's air quality guidelines state air pollution should remain below 50.

"Many people believe that when the AQI is below 160 the benefit of doing sports and exercise outweighs the danger of being exposed to air pollution," Floris says.

This philosophy is backed up by US-based doctor Richard Saint Cyr who spent 10 years working at Beijing United Family Hospital and writes regularly about managing air pollution.

Dr Saint Cyr believes that up to a point outdoor exercise offers "much more benefit than harm" when a mask is worn.

Sydney has been blanketed in thick smoke for days. ( ABC News: Catherine Taylor )

What about children?

The developing lungs of small children can be most vulnerable to pollution and smoke.

Some Sydney schools — including Newport and Stanmore Public Schools — have kept students inside during recess and lunch in recent days in an effort to reduce their exposure to smoky pollution.

And many weekend sporting clubs for children advised parents to be prepared for matches to be cancelled over the weekend if pollution rises.

China's most expensive schools now market their ability to deliver near perfect air quality in classrooms.

"My children's school has a state-of-the-art air purifying system," says Floris. "Whenever a door is open the 'bad air' is pushed outside. This guarantees an indoor AQI of about 1."

These elite schools also offer one or even two sporting "domes" — giant inflatable structures that contain tennis or basketball courts and even soccer pitches and are pumped full of purified air so children can breath clean air while they exercise.

Once air pollution hits 200 on the air quality index a series of bell combinations signals to students that they are not to go outside, or that they can walk from main buildings to the sports domes.

Same view from Lise Floris's Beijing apartment on different days ( Supplied: Lise Floris )

For Floris, managing pollution has become a routine part of life and "is not defining our everyday lives in Beijing". But she is wary of moving to another polluted city when the family's expat contract ends next year.

"We do miss clean air and occasionally dream about the forests and parks back in Europe," she says. "We had the opportunity of applying for a position in Delhi after Beijing but for me, that was a no-go simply because we've seen a huge improvement in air quality in Beijing over the past four years. From what we hear, the Indian government is not taking the same measures."

But what about the air inside?

So you've followed the advice and have stayed in doors all day. Yet closing the windows and doors is not enough to stop those tiny air pollution particles from finding their way inside.

A A device like this will record the air pollution level inside the house. A figure of 42 means you can breath easy. ( Supplied: Kaiterra )

As indoor air quality monitors — another appliance that most middle-class Beijing families have at home — make clear, smoke and pollution particles can sneak inside.

"Air purifiers are the most valuable item we own for making life with pollution bearable," says Floris. "We live on the seventh floor of a city apartment block so as soon as we wake up we can gauge the level of pollution depending on which skyscrapers are covered in smog. We know when to turn on the purifiers. We have six of them in our apartment and on bad days they will be running on high all day."

Floris says on days when pollution is bad she will often work at home and not leave the house.

Dodging air pollution causes such anxiety in Beijing that restaurants and cafes are now starting to market their air quality credentials. And one of Beijing's most high-end malls, Parkview Green, spruiks its filtered air to attract shoppers.

If pollution descends for several days at a time Chinese authorities issue a "red alert" which closes schools and restricts traffic.

How will buildings need to change?

We're already talking about how to better bushfire-proof regional homes. But how do we future-proof our houses if the haze is here to stay?

According to the experts, the best way to stop smoke from getting in is to ensure that, well, nothing can.

They point to the Passivhaus design as a model we should — and probably will — be looking at more closely in the future.

The Fern in Redfern is the first Passivhaus apartment block in the southern hemisphere. ( Facebook: Steele Associates )

The German concept uses high-performance glazing, insulation and an airtight building envelope to control the internal temperature.

Think of it like a vacuum seal, with no heater, air conditioner or afternoon breeze required.

"Highly developed countries [have] all gone down the route of air-sealing buildings for energy efficiency and having controlled ventilation systems to make sure you've got good air quality all the time," says Jesse Clarke, an engineer and building science manager with Pro Clima.

"And we're just a few decades behind."

The Fern had to be about 40 times more airtight than the average NSW home. ( Facebook: Steele Associates )

It's something Oliver Steele knows all too well. The Sydney developer designed the first Passivhaus apartment block in the southern hemisphere — The Fern in Redfern — to combat air pollution problems.

"Getting the level of air tightness required... you have to have it 40 times more airtight than the average NSW home, and that was something that had never been done in apartments before," he said.

Mr Steele — who used the Passivhaus design when building his own home — said the recent smoke pollution had shown it was a viable option.

"In these bushfires, I walked out the door and was just struck, it smelt like I was standing next to a campfire, whereas inside I couldn't smell anything," he said.

How does fire management need to change?

Researchers credit the comparatively low level of fatalities this fire season to emergency services, and improvements in their warning systems in the decade since Black Saturday.

But Richard Thornton, CEO of the Bushfire and Natural Hazard Cooperative Research Centre, says there's always more that could be done — including a national fire rating system that's currently in the works.

"We're going to be struggling for a few years, so that does mean that as a community, we need to think about what we want to do about that," Dr Thornton says.

"There are things we can do in terms of fuel reduction... [but] those windows for safely doing prescribed burning are getting more difficult."

According to Professor Bowman, the current smoke haze is an indicator of "something that's wrong with our fire management".

He says while planned burning is an important tool in managing fire hazards, the inevitable side effect is more smoke pollution.

"Planned burning is also injurious to people and it can actually cause more harm than flames from bushfires, so you've got a paradox," he says.

"It's a very complicated trade off."

Professor Bowman says the answer going forward likely lies in alternative forms of fuel management.

Professor Bowman says planned burns are an important tool, but it does create smoke pollution. ( Supplied: NSW Rural Fire Service )

"Where we try to reduce the amount of smoke emissions, particularly around our suburbs and cities... so really, a complete redesign of [our] thinking."

Dr Thornton says it's a discussion that will need to take place, one way or another.

"It's a matter of do we have smoke from prescribed burning or smoke from uncontrolled wildfires during the summer? That balance is something we still need to have a conversation around."