Comments on: Keep my hot tub at 98.6F, please!

Question: Keep my hot tub at 98.6F, please!

gregvr — Thu, 29 Jun 2006 13:36:18 -0800

I've been reading a fiction book set in Antarctica, which goes into a lot of detail on frostbite, severe cold, etc. One of the characters gets caught in an underground hot spring, but thinks that he is safe because the water is relatively warm. His companion says that "human beings can die of hypothermia even in a bath at 90F if they are immersed long enough." Could this really happen?

It seems that even though, yes, you will be losing heat to the environment at a much higher rate than you would in air, the delta T just seems so slight!

What temperature water is generally considered REALLY dangerous to be immersed in for a long period of time?

By: Tubes

Tubes — Thu, 29 Jun 2006 13:43:39 -0800

I know a guy who got hypothermic in his outdoor hot tub. Fell asleep in it, in the winter, and the tub heater couldn't keep ahead of the cold indefinitely. Eventually it dropped below body temp and dragged his temp down with it, to about 92 if I recall. I don't remember if someone found him there, or if reflexive shivering and chattering finally woke him up.

By: edd

edd — Thu, 29 Jun 2006 13:48:53 -0800

That's borderline, but yes according to this link.

By: adamrice

adamrice — Thu, 29 Jun 2006 13:49:32 -0800

Yes, it can happen, or something like it—I don't think it's hypothermia per se, but basically you are in a medium that wicks away heat. It was a concern for Diana Nyad when she swam Florida-Cuba, despite the fact that the Carribean waters were quite warm.

You're right that the delta-T is slight, but if you stay there long enough, it becomes significant.

According to the wikipedia article on hypothermia, "Children can die of hypothermia in as little as two hours in water as warm as 16°C, typical of sea surface temperatures in temperate countries such as Great Britain"

By: frogan

frogan — Thu, 29 Jun 2006 14:31:27 -0800

Water is something like 1000 times denser than air, and therefore wicks away heat at an astonishing rate. When it feels "warmer" in cold water than in cold air, what you're feeling in the cold air is the evaporation of water on the surface of your skin (the same thing as sweating). You don't feel that evaporation when submerged, so you *think* you're warmer than you are.

By: prjo

prjo — Thu, 29 Jun 2006 14:32:57 -0800

I remember hearing that you are in danger of hypothermia if the air tempeture and water tempeture add up to less than 150.

By: SassHat

SassHat — Fri, 30 Jun 2006 00:57:48 -0800

When I was in high school, we did a whole unit on winter hiking and hypothermia. The general rule I think everyone has learned is hypothermia is a combination of wet, wind and cold. And if the conditions are wet and windy, eventually your body temperature will drop, no matter if it's the heat of summer or the dead of winter.

But I think if you were immersed in a bath at 90 degrees, it would take a while, since I'm assuming only your head would peek out...but then you lose the most heat from your head, I guess. Yeah, it could happen. But it would take a while, I bet.

By: azuma

azuma — Fri, 30 Jun 2006 20:13:14 -0800

gregvr - could you tell us the name of the book? I wouldn't mind reading it.