Regulating indoor or equipment air—temperature, humidity, and ventilation—or the systems/devices used for that; often used synonymously with 'air conditioning' (空調).
夏は空気調節のために窓を閉めることが多い。
In summer, we often close the windows to regulate the air.
オフィスの空気調節が故障して、みんな暑そうだった。
The office's air-conditioning was broken and everyone looked hot.
新築のビルは最新の空気調節システムを導入している。
The new building has installed the latest air-conditioning system.