air clean clean air clouds cloudy concept cool day hot Morning nature pollution sky sphere summer sun architecture brick bricks chimney duct emission emissions exhaust pipe high industrial industry pollute production red smog smoke smokeshaft tall trees exhaust pipe industrial smokestack smokestack atmosphere climate contamination cranes energy environment exhaust fumes factory fume funnel gas industrial workplace plant reek steam toxic work chimney-stalk cloud crevasse ecology green habitat smoke-stack stack vent boats china city dirty ferry Hong Kong island ocean sea ship sunny tourism travel blowing blue carbon chemical dioxid effect greenhouse heaven oxygen warmth white wind