Last month visibility in Harbin dropped to below three metres because of heavy smog. On days like these, no surveillance camera can see through the thick layers of particles, say scientists and engineers.
Existing technology, such as infrared imaging, can help cameras see through fog or smoke at a certain level, but the smog in some Chinese cities is a different story. The particles are so many and so solid, they block light almost as effectively as a brick wall."
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