Ключевые слова: air, background, burn, chemical, chimney, city, coal, danger, ecology, energy, environment, factory, fireplace, firewood, foundry, fuel, furnace, gas, heat, heavy, hot, industrial, industry, landscape, light, manufacturing, metal, oil, old, orange, oven, pipe, plant, pollution, power, production, red, refinery, silhouette, sky, smog, smoke, steam, steel, sun, sunrise, sunset, technology, work, yellow,