Atmospheres absolute (ATA) is a standard way to measure the amount of air pressure in a hyperbaric chamber. The common starting point is 1.0 ATA, which is the weight of the earth’s total atmosphere we experience while standing at sea level. If we were to dive into 33 feet of seawater, the sum of both the water and atmosphere’s weight would equal 2.0 ATA. At 66 feet it would be 3.0 ATA, and so on. In a hyperbaric chamber, this phenomenon is replicated through the combination of an airtight container and a continuous inflow of pressurized air.