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JHH60 wrote:

Buz Groshong wrote:Not quite true. The gage pressure will be the same, but the absolute pressure, which determines the boiling point will be correspondingly lower. It will cook slower at altitude than at sea level, but faster than an open pot at sea level.

Example: If the pressure cooker maintains 15 psi (103 kPa) gage pressure, absolute pressure will be 30 psi (206 kPa) at sea level and about 23 psi (158 kPa) at 14 k (4300 m).

I stand corrected. But unless I'm wrong (and sources I quickly checked on the internet are also wrong ) the increase in cooking time at altitude vs. sea level will be a lot less in a pressure cooker than in an open pot. If your cooker raises the pressure by about 1 bar gage, then if you're up at 3000m where the pressure is .7 bar (70% of what it is at sea level), then the absolute pressure inside the cooker will be 1.7 bar (85% of what it is at sea level). Checking some handy engineering tables, I find that the boiling point of water inside the cooker at 3000m should be 114C (vs. 120C at sea level), whereas it would be 80C in an open pot (vs. 100C at sea level).