Beijing, Sep 28. AQI has soared from yesterday's blue-skies-'good' to a grey-and-gloomy-'unhealthy'. My neighbours are doing some sort of extraordinary construction project which seems to entail them trying to pull down half of the balcony they've built on the rooftop of the building. The national holiday next week has to be 'earned' by working the weekend so the kids at the school out the front are doing their thing. Which means this smoggy sunday morning is soundtracked with clanging, scraping and banging, alongside chanting children and calls from teachers. I'm going back to North Korea the day after tomorrow.