On the heels of record smog in Hong Kong comes a novel idea for clearing the air: Make buildings the “lungs of the city.”
In effect, they may already be performing that function, said Elia Sterling, president of Theodor Sterling Associates Ltd. in Vancouver, a pioneer in the field of indoor air quality.
Recent tests inside four Hong Kong skyscrapers revealed that the indoor levels of particulate matter were 70 percent lower than outdoor levels, Sterling said. The buildings, with their massive ventilation systems, were acting as oases from the smog.
Why not expel their clean, filtered air into the smog at street level instead of off the rooftop? Sterling wondered.
“There’s an opportunity we’re not taking advantage of,” he said. “A lot of the main floors of buildings in Hong Kong are open to the air, like a pedestrian mall. You could just supply the cleaner air into that space and create a clean-air bubble zone around buildings and in adjacent public spaces.”
According to the Clean Air Network, a Hong Kong-based nonprofit group, the air in Hong Kong, a city of 7 million, is three times more polluted than the air in New York, a city of 19 million. Hong Kong’s smog during the recent fall and winter quarters, ending in March this year, was the worst on record. Sandstorms from China played a role in the thick haze, but so did traffic exhaust and the smoke from factories and power plants in Hong Kong and the nearby Pearl River Delta region, a major export hub.
Particulate matter, among the most harmful of all air pollutants, is a mixture of tiny particles from car exhaust, wood-burning stoves, construction dust, industrial smoke and the dust from open lands. When inhaled, the particles can evade the natural defenses of the respiratory system and lodge deep in the lungs. Particulate matter can cause and aggravate bronchitis and may increase the number and severity of asthma attacks.
Typically, fresh air forms at least 20 percent of the indoor air supply of large buildings. It gets filtered when it enters a building and passes through many more levels of filtering before it is expelled as much cleaner air from the rooftop.
“People spending their time in buildings are significantly less at risk than people who are outside on the streets of Hong Kong,” Sterling said.
And not only in Hong Kong. In reviewing seven years’ worth of air quality data from 200 buildings across Canada, Mike Glassco, the operations manager of Sterling Associates, found that, on average, the levels of indoor particulate matter were between 45 percent and 62 percent lower than outdoor levels.
Glassco estimates that 100 well-ventilated buildings in Canada can remove about 1,700 pounds of particulate matter from the air every year, roughly the amount produced by 4,300 cars. In Hong Kong, where the outdoor air is much dirtier, he said, 100 well-run buildings would have an even greater impact on air quality.
There’s obviously no substitute for cleaner cars and factories, but making better use of the clean air from buildings could help, Sterling said. It’s worth testing the “lungs of the city” hypothesis over a larger number of buildings in multiple cities, he said.
“Particularly in China, where urbanization is happening at a rapid pace and industrial emissions are a large part of the air quality challenge, applying the ‘lungs of the city’ effect for town planning could be very beneficial for human health,” Sterling said.