Ключевые слова: background, blue, boiler, building, clean, conservation, construction, ecology, energy, engineering, environment, environmental, factory, full, gas, green, heat, industrial, industry, iron, liquid, machine, maintenance, metal, nobody, pipe, pipeline, plant, pollution, power, process, purification, purified, purity, service, sewage, sewer, sewerage, steel, storage, structure, system, technology, treatment, tube, valves, waste, wastewater, water,