Diving organizations such as PADI® or NAUI provide certified recreational scuba divers with a dive table to determine how long a diver can stay underwater at a given depth, both for the initial and subsequent dives. The reason for the dive planner is to ensure that the amount of nitrogen your body absorbs during a dive remains within acceptable limits.
Dive tables do not tell you how much nitrogen has accumulated in your body after a dive; they simply tell you how long you can stay at a given depth without having to have a mandatory decompression stop.
Recreational dive tables come in the form of a plastic coated card, and for many recreational divers these cards are daunting and look very complicated. For example, the PADI® dive card has tables on both sides of the card, containing over a thousand numbers.
At Wolfram|Alpha we have removed the complexity of trying to read the NAUI and PADI® dive tables.
Psychrometry deals with the thermodynamic properties of gas-vapor mixtures. Air-water vapor mixtures are the most common systems studied because of their importance in heating, ventilating, air conditioning, and weather reporting.
Students of engineering are introduced to the subtleties of psychrometry in their thermodynamics courses. But we are all exposed to psychrometry any time we watch weather reports on television. Your favorite meteorologist probably speaks about the relative humidity, dry bulb temperature, and dew point temperature.