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At 10:53 AM 7/18/00 +0000, stuart.morrison@sw*.co*.uk* wrote: Hello Stuart, >So my question is, is the speed of altitude change important even if the >altitude itself is "safe"? If I can feel a rapid pressure change in my >ears, is it doing anything to my tissues? > >I've never seen the rate of change mentioned anywhere but I'd imagine it >must play some part. If the maximum altitude you'll reach after the dive is < ~2000 feet, you *probably* don't have anything to worry about. In general, you don't have to modify your tables for altitude dives at less than 2000 feet above sea-level since the pressure difference from top-to-bottom is very small... equivalent to just a few millimeters of water. The rate of change wouldn't be a significant factor either for the same reason; the pressure differential from 2000 feet to sea-level is about the same as from the surface of the water to a few millimeters below the water. You traverse those few millimeters of water in a fraction of a second yet traverse the 2000 feet through the air at a much slower rate. It's safe to traverse the gradient in the water so it's safe to do so through the air as well. In fact, a weather system that changes the barometric pressure by one inch of Hg changes the pressure altitude by ~1000. -Mike Rodriguez <mikey@mi*.ne*> http://www.mikey.net/aue Pn(x) = (1/(2^n)n!)[d/dx]^n(x^2 - 1)^n -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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