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ME professor interviewed by New York Times on Effectiveness of Smog Mask in Combating Pollution

Prof. Wallace Leung, Chair Professor of Innovative Products and Technologies in the Department of Mechanical Engineering (ME) has been interviewed by New York Times on smog mask in combating pollution as it has been a serious, hot issue especially for major cities in China. The following is an excerpt of the NY Times article and the full article can be read from:



When smog descends on Beijing or other Asian cities, people rush to buy face masks. But how effective are the masks at filtering out tiny, harmful particles of pollution? Prof. Leung’s tests found that at a standard airflow velocity, basic masks captured only 20 to 25 percent of tiny particles of 50 to 500 nanometers — a size common in diesel vehicles’ exhaust. Such particles, less than 1 percent of the width of a human hair, are of particular concern because they can get buried deep in the lungs and end up in the bloodstream. The figures do not include any gap between the mask and the face that allows air to come in, further reducing efficiency.

“What it means is, if you wear a face mask, you get 75 to 80 percent into the body,” Prof. Leung said. “So that’s not good.” A better bet is respirators that guard against at least 95 percent of small particles. Sometimes known as N95 respirators, they use thick layers of polypropylene and are designed to fit tightly to the face. But respirators that guard against small particles can make it more challenging to breathe.

To improve breathability and increase filtering efficiency at the same time, Prof. Leung wants to create masks and respirators that use multiple layers of nanofibers. He received a United States patent last year, and “a number of companies have approached us,” he said.

Another issue is that while N95 respirators guard against small particles, they do not combat another form of traffic-related pollution: gases like nitrogen oxides or volatile organic compounds. Some companies have created cartridges that can connect to certain respirators to block some gases. But they are expensive and cumbersome —not a good choice for the public in Asia.

Prof. Leung hopes to create a system that uses sunlight and oxygen to turn nitrogen oxides and volatile organic compounds into “harmless substances, like carbon dioxide or water.” Eventually, he hopes to be able to join it to a regular, particle-filtering respirator.