In the Hornbostel-Sachs classification system, it is a membranophone. Drums consist of at least one membrane, called a drumhead or drum skin, that is stretched over a shell and struck, either directly with the player's hands, or with a drum stick, to produce sound.
Heat production can be calculated from a measurement of VO 2 and/or CO 2. Doubly-Labeled Water Doubly-labeled water contains isotopes of oxygen and of hydrogen. The technique involves the consumption by the patient of the doubly-labeled water then the measurement of the amount of isotope in the person after a washout period of 7- 14 days. Most of the hydrogen and oxygen isotopes are lost through excretion and evaporation, but some of the oxygen isotope equilibrates with carbon dioxide and is expired in air.
Of course not water doesn't go bad. Having a freshness date on a bottle of water makes about as much sense as having an expiration date on sugar or salt. There are several reasons why water bottles come with an expiration date. The main one is government bureaucracy: water is a consumable food product, and as such, it is subject to laws requiring expiration dates on all consumables, from bologna to lemonade.