空気 and 酸素: air and a component of it
Distinguish air as a whole from oxygen as a component, and physical air from figurative atmosphere.
Air as a whole
空気, read くうき, means air. 窓を開けて空気を入れ替えました。 means opening a window to exchange the air.
空気の流れを調べました。 means investigating airflow. It does not mean measuring the concentration of a particular component.
Oxygen as a component
酸素, read さんそ, means oxygen. 空気には酸素が含まれています。 says that air contains oxygen.
酸素の量を測りました。 means measuring the amount of oxygen. Do not change the measurement target to all the air.
Figurative atmosphere
会議の空気が変わりました。 can mean that the atmosphere of the meeting changed. Do not necessarily interpret this as a change in gas composition.
空気を読む means reading the mood. Substituting 酸素を読む does not preserve the idiom.
Can 酸素を読む replace 空気を読む with the same meaning?
Show the answer and why
No. The idiom for reading the mood uses 空気.