in fact, that is the concentration of carbon dioxide you regularly breathe if you work in a new energy-efficient office building, for that is the level established by the engineering group that sets standards for heating and ventilation systems.

이 문장에서 for는 접속사인거같은데 because 의 의미로는 해석이 안되서요 for를 어떻게 봐야되는거죠? 알려주세요 ~