Complex sentence: The first practicable scroll compressors therefore did not appear on the market until after World War II when the development of higher precision machine tools permitted their construction and were not commercially produced for air conditioning until the early 1980s.
Split into simpler sentences: The first practicable scroll compressors did not appear on the market until after World War II higher-precision machine tools permitted their construction. They were not commercially produced for air conditioning until the early 1980s.