Work period of current is big, copper wire high temperature (550 degrees), if the working section has air exist, copper and oxygen in heating conditions produce copper oxide.

工作段电流大，铜线温度高(550度左右)，如果工作段内有空气存在，铜和氧气在加热的条件下就产生氧化铜。

youdao

A 1 per cent loss in productivity by employees who are dissatisfied with work conditions equates to almost four times the average cost of heating or air-conditioning the entire building.

由于员工对工作环境不满而导致每1%的生产率下降就近乎给整栋大楼提供暖气或空调所花去平均费用的四倍。

youdao