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Charles' Law
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Charles' Law “At a constant pressure, the volume of a gas varies directly with the Kelvin temperature”
Charles' Law is expressed by the equation:
"William Browning" was a successful businessman. To this day his Southern Oregon winery rivals even the finest Napa Valley vineyards. Unfortunately William isn’t able to enjoy the success of his labor, since an unfortunate diving incident took his life over two decades ago. Always an independent type, William enjoyed the fact that the Army Corp of Engineers considered him the local expert when it came to underwater work. They knew that if anyone could do the job, it was he. So when the Corp approached him to do some deep work in a new lake formed by their latest dam project, he jumped at the opportunity. The job entailed attaching dock cables to pre-poured moorings on the bottom of the boat ramp at the new McGregor Park. The approach was quite steep and while it ended in approximately 150 feet of water, the bottom tapered down from that point to the over 300 foot deep riverbed below. Visibility was near nil, “I can’t even read my gauges”, as are most newly filled lakes, and the bottom was reported to be quite cold. Since the lake was filled by melting snow and runoff from North Americas’ deepest lake, the temperature was estimated to be hovering just a few degrees above freezing at the 150 foot depth. William was prepared with the appropriate coldwater exposure suit and lots of weight to keep him in place while working on the steep incline. It was a beautiful, hot day as William was finishing up the project. Rarely one to employ a safety diver, he was utilizing the assistance of friends and bystanders to fetch his tanks and equipment whenever he surfaced. Prior to one of his last descents, he complained of a “screaming headache”, and stated he needed to hurry up and get the job done before it worsened. One of the kids helping him noticed that the tank he was sent to the beach to fetch was hot to the touch from sitting in the sun. It showed less than 500 lbs. on the gauge. Indicating that he only had 5 minutes or so left to do at the 100 + foot depth, William stated that there would be plenty of air for him to complete the mission. Witnesses watched his bubbles trail out to the end of the dock and cease less than 4 minutes after he entered the water. An exhaustive two-week search ensued utilizing both local and regional divers as well as the latest in underwater video equipment from Canada. Equipped with over a million candlepower floodlights, the most the underwater rover could see was 2 to 3 feet ahead. To this day, nearly 20 years later, no traces of William’s body or equipment have been found in Lost Creek Lake. What Happened? A lot of debate has occurred since that day regarding what happened, and what was done wrong. Numerous factors have been suggested as possibly contributive including: Not diving with a buddy or safety diver, the bends, air emboli, entanglement, hypothermia, nitrogen narcosis, fresh water diving at altitude, the list goes on. Of course these are all speculation. One thing we know for sure is what Charles’ Law says about gasses and temperature. 500 lbs. of air in a tank on the beach, in 100 degree F heat is going to equal something significantly less at a depth of 100 feet in 40 degree F water. That, coupled with the decreased visibility inhibiting William’s inability to check his gauges, and the fifty+ pounds he was hefting preventing a rapid ascent couldn’t have helped his odds much. What Can I Learn From This? I won’t harp to you regarding the merits of buddy diving and following the appropriate dive tables and/or computers. I think those subjects are covered relatively well in most certification classes these days. However, with summer upon us I cannot stress enough the effects heat has on the volume of gas available in your scuba tank. Shore diving often involves utilizing tanks that have been either sitting in the sun, or the trunk of someone’s vehicle, where temperatures can soar to well over ambient. The readings you get regarding available air can not only be deceptive, they can be downright dangerous. Keep your tanks in the shade whenever possible to avoid overheating, (which can also pop diaphragms and ruin your whole day). When that isn’t possible, pre-cool your tanks by immersing them in the water where you will be diving, and check your gauges more frequently than normal when you know there is a significant difference in temperature between the surface and your diving depth. by Gordon Brown |
