After The Deep Sea Desperados received their equipment from www.divingislife.com, it was time to make the final preparations for the dive. Before a dive takes place, Mac and Chanel determine the air tank sizes they are going to use and also calculate their Surface Air Consumption rates also known as "SAC Rates." Surface Air Consumption or sometimes called surface gas consumption is the measure of your rate of gas usage expressed in pounds per square inch or psi. This essential calculation often leads to the most popular question divers ask, "How long will an air tank last?"