Sponsored social media advertisements promoting gas masks could be the first sign of a “new horrible normal” in Sydney as the city chokes on toxic smoke.

The unusual targeted advertising comes as rural fire brigades in New South Wales ask for donations to pay for more firefighting masks as they tackle major bushfires raging across the state.

But an environmental health expert has warned masks can “create a false sense of security” against dangerous air pollution, and urged people to avoid heavily relying on them.

So far, six people have died and more than 720 homes have been destroyed over the unprecedented fire season.

Bushfires along the east coast are still burning from the south coast of NSW right up to the border of Queensland.

While bushfire smoke is nothing new for rural firefighters, Sydney residents are struggling to cope with the thick layer of toxic air that has enveloped their seaside city.

On Tuesday, air pollution was so bad that Sydney’s air quality index (AQI) catapulted as high as 12 times hazardous levels in some areas.

The Bureau of Meteorology is predicting the smoke will linger all week.

Many Sydneysiders have aired their concerns on social media, with one woman expressing horror at finding new sponsored ads promoting gas masks on her Instagram feed.

“Getting these ads on Instagram is the new horrible normal,” Una Butorac tweeted.

https://twitter.com/unabutorac/status/1204364275533266944

Another hazardous air quality today in Sydney. I’ve never seen it like this before. Stay safe and indoors. #AustraliaBurns #bushfiresNSW #nswbushfire #sydneysmoke pic.twitter.com/ViznXNPprJ

— Crazy Is The New Black (@JimVillamor) December 10, 2019

Sydney resident Isabelle Osborne said the air had been so thick and hazy that on some days she couldn’t even see the building next door from the window of her workplace.

“(The smoke) really irritates your eyes, throat and nose … I am avoiding going outside at all costs,” Ms Osborne told The New Daily. 

“It’s starting to feel like it’s never going to end. Now I’m concerned, is it going to be like this all summer?”

She said it was common to see people wearing masks outside.

Bunnings regional operations manager Robyn Hudson said the hardware store had been working hard to restock stores with masks to keep up with increased demand.

“We’ve had great support from our suppliers and we’ve been working closely with them to get more masks into impacted areas,” Ms Hudson told The New Daily. 

“Team members are unpacking deliveries as quickly as possible and moving masks to the front of stores to make them easier for customers to find.”

But a public health expert has urged people in Sydney to avoid relying on masks for protection from air pollution.

Sotiris Vardoulakis, a professor of global environmental health at the Australian National University, said only professional face masks that fitted tightly around the wearer’s mouth and nose were effective at reducing smoke inhalation.

“Don’t over-rely on masks though because sometimes they create a false sense of security and can cause terrible discomfort or difficulty breathing,” Professor Vardoulakis told The New Daily. 

“Face masks are important for people who have to work outside, but ideally people should avoid exposure by staying indoors.”

He said NSW’s “explosive” bushfire season was undeniably related to climate change, and warned drier conditions would cause more “severe bushfire episodes” in the future.

The best thing to do during periods of prolonged air pollution is to stay inside, use an air cleaner with an HEPA filter, and avoid strenuous exercise, he said.

Young children, the elderly, pregnant women, smokers and people with existing conditions like heart and lung disease are more vulnerable than others to the effects of smoke.