air level

air level (plural air levels)

1. (dated) A spirit level.
2. Used other than figuratively or idiomatically: see air,‎ level.

   When diving, take care to monitor not just your air level, but that of your partner.

• “air level”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.

• Valliere