"Beijing has invested heavily to build up a nationwide surveillance network that lets police watch every major street and corner in main cities.
But with smoggy days becoming more frequent, the effectiveness of the system has been greatly compromised. Some fear terrorists may choose a smoggy day to launch attacks."
Chinese experts are working feverishly on a solution: "Our preliminary research shows that the smog particles are quite different from the small water droplets of fog in terms of optical properties. We need to heavily revise, if not completely rewrite, algorithms in some mathematical models. We also need to do lots of computer simulation and extensive field tests."