Ключевые слова: air, atmosphere, blue, blue sky, carbon, carbon dioxide, chemical, chimney, climate, cloud, coal, contamination, damage, danger, dirty, ecology, electricity, emission, energy, environment, environmental, environmentally friendly, exhaust, factory, fuel, fume, gas, global, industrial, industry, manufacturing, nature, ozone, pipe, pollute, pollution, problem, production, refinery, sky, smog, smoke, smokestack, steam, technology, toxic, tree, white, white smoke,