These new industrial cleaners are much lower in ammonia and other dangerous chemicals than before.这些新型的工业用清洁剂中，氨和其他危险的化学物质含量都较以前的低很多。Office vacancy rates have reached a low, pushing rents up sharply for office and industrial space.办公室空置率降到很低，使得办公室与工业用房的租金急剧上涨。