fixedchina is cloaked in smog and the number of particles in the air are 20 times the level considered safe by the world health organization. reporter: in beijing, it has become part of daily life, checking how fit it is to spend time outside. chinese authorities have advised people to stay indoors and for .chools to stop classes >> we are concerned about the large impact it will have on held early people -- elderly people and children. children want to go out and play. i think the government needs to put more effort into solving this. have a bigl actually impact on the schoolteaching timetable. students and parents are all concerned as to when we can finish a teaching assignment and whether the holidays will be pushed back. an almost complete lack of wind means the smog lingers over the city. the deadliest airborne particles are more than 20 times the level considered safe. >> according to our forecast, the concentration of pollutants in the air will rise to severely polluted levels on saturday afternoon or evening and continue until tuesday. the air quality is expected to become bett