Delta P, shown as ΔP, is a symbol that simply denotes changes in pressure. However, when found underwater, Delta P can be deadly, and even minute lapses of judgment have caused fatal accidents. When two bodies of water come together and one has a higher pressure than the other, the high-pressure water will always try to move to the lower-pressure water to create equilibrium. This basic idea has created many problems with divers working underwater. If a diver is in a high pressure body of water and a connection to a lower pressure body of water suddenly opens, the diver will be pulled along with the force of the readjusting water. If the connection between the two bodies of water is small, the diver can get sucked onto whatever is connecting the bodies of water; since potentially thousands of pounds of pressure are trying to go through the connection, the diver is pinned and unable to move before they drown.
There are numerous, devastating examples of divers working underwater and losing their life to Delta P. Many times, the diver is cleaning blockage between two bodies of water, but when the blockage is cleared a connection is opened up and the diver is trapped as water rushes through. In 1989, three divers in Maine had been working on clearing a filter inside a dam, and when the filter was cleared out water instantly began to rush through and one of the divers was pinned onto the filter. A second diver swam to attempt to rescue the first diver when they also got trapped on the filter. Eventually, the third diver was able to pull up the other two to the surface but enough time had passed for both to have drowned.
While laws have been passed to prevent future accidents, historically, Delta P has caused injuries and death – even in recreational pools. People happened to be near uncovered holes that had water flowing into them due to pumps and their bodies would cover up the hole and get stuck due to suction. Delta P is a terrifying, yet uncommon killer. Proper safety precautions are imperative when diving, and Delta P is only one of the threats to look out for.
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