# Why 15 psi max on pressure cookers? **URL:** \ **Category:** Factual Questions\ **Created:** [December 30, 2006, 10:20pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149 "2006-12-30T22:20:14Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![nolonger\_lurking](https://avatars.discourse-cdn.com/v4/letter/n/41988e/32.png) [@nolonger\_lurking](https://boards.straightdope.com/u/nolonger_lurking)\ **Post date:** [September 29, 2011, 3:23am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/21 "2011-09-29T03:23:28Z")
> [@Rocketeer](#): > > Your air compressor isn’t full of superheated steam, either. A steam explosion is much much worse than a compressed-gas explosion. There is a reason for the backronym for [BLEVE](http://en.wikipedia.org/wiki/Boiling_liquid_expanding_vapor_explosion) “Blast Levels Everything Very Efficiently” ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 29, 2011, 2:24pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/22 "2011-09-29T14:24:16Z")
> [@minor7flat5](#): > > Robustness of the vessel aside, the difference would be the saturation temperature of water at the target pressure. > > Your 15psig (g=gage pressure, add 14.7psi for absolute pressure) pot has a saturation temperature (boiling point) of around 250F. Bumping the pressure up to 90psig gets you a saturation temperature of 331F. > > I’m not sure what effect that would have on the food you are cooking, but that would be the physical difference. Imagine a pressure cooker 12 inches in diameter. At 15 psig, the force trying to remove the lid is about 1662 pounds. Not only does the lid need to be strong, but the retention mechanism as well. Plus the bottom of the pot, which experiences the same total force, needs to remain relatively flat. bump up the gauge pressure sixfold, and you need some very thick material to ensure that the bottom remains flat and the lid stays on. Given the safety concerns with respect to a potential BLEVE, a cooking vessel rated for 90 psi would be very heavy and very expensive, and will include a surcharge to provide the manufacturer with a hefty liability insurance policy against the inevitable fatal cooking accident that will occur when a user does something wrong or the cooker suffers a mechanical failure (sell 100,000 units, and someone somewhere somehow will have a problem). ---
**Author:** ![muldoonthief](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muldoonthief/32/3188_2.png) [@muldoonthief](https://boards.straightdope.com/u/muldoonthief)\ **Post date:** [September 29, 2011, 2:27pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/23 "2011-09-29T14:27:24Z")
> [@Malacandra](#): > > What temperature kills zombification spores, anyway? No kidding, I was shocked then saddened to see **David Simmons** post to this thread. ---
**Author:** ![Borzo](https://avatars.discourse-cdn.com/v4/letter/b/43a26b/32.png) [@Borzo](https://boards.straightdope.com/u/Borzo)\ **Post date:** [September 29, 2011, 2:51pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/24 "2011-09-29T14:51:12Z")
> [@AaronX](#): > > My friend managed to open a pressurized pressure cooker once… Why would someone do such a thing? ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [September 29, 2011, 3:10pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/25 "2011-09-29T15:10:17Z")
> [@AaronX](#): > > My friend managed to open a pressurized pressure cooker once, I heard there was food left on the ceiling. His hand and face got burnt, but he recovered ok (some scars, no loss of function). Another anecdote. My mother used to can using a pressure cooker. One time she did something wrong, I don’t know what, but the safety cap blew and left a dent in the ceiling. If that could happen with a standard kitchen pressure cooker, what kind of damage could have happened with a malfunctioning/user error high pressure cooker? ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [October 5, 2011, 2:02am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/26 "2011-10-05T02:02:08Z")
> [@Borzo](#): > > Why would someone do such a thing? He didn’t know how pressure cookers work, or that you’re supposed to depressurise them before opening. ---
**Author:** ![Saintvamp](https://avatars.discourse-cdn.com/v4/letter/s/c89c15/32.png) [@Saintvamp](https://boards.straightdope.com/u/Saintvamp)\ **Post date:** [January 22, 2015, 4:43am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/27 "2015-01-22T04:43:26Z")
I would think it has to do more with what was capable back when the recipes were invented (cost to make for the general population to purchase) and that the FDA found that cooking at 220 235 250 degrees F. for specific times killed specific bacterias found in foods making them safer for human consumption. Safety laws involving pressurized vessels came into effect after pressure cooking / canning was put into general practice so any laws were probably made to exclude pressure cookers and canners. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [January 22, 2015, 2:44pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/28 "2015-01-22T14:44:50Z")
> [@Jinx](#): > > Actually, anything above 15 psig would be considered a pressure vessel by ASME Code and require to be regulated (inspected) under state and/or Federal law. Small vessels receive a “UM” stamp, IIRC, and large vessels over some threshold require a “U” stamp. Also, pressure vessels require a pressure relief valve which has its own cycle of required ASME certified inspections. Oh, and Napier, yes the pressure rating is for a specified temp as temps above the rated temp will weaken the pressure vessel wall material, Those stamps are for \*\*Unfired \*\*Pressure Vessels. The pressure cooker is a fired vessel. ---
**Author:** ![FRE0](https://avatars.discourse-cdn.com/v4/letter/f/9de053/32.png) [@FRE0](https://boards.straightdope.com/u/FRE0)\ **Post date:** [October 21, 2015, 10:49pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/29 "2015-10-21T22:49:06Z")
I have unsuccessfully attempted to find a pressure cooker that can be operated at more than 15 psi, perhaps 30 psi. Obviously it would cook faster, but they don’t seem to be available. 30 psi is not especially high; I have an air compressor that goes up to 125 psi and it does not require any special permits. Pressurized water nuclear reactors operate at around 1,500 psi. Charles Darwin, the scientist who wrote about evolution, discovered the need for pressure cookers when he was on an expedition at high altitude. Potatoes remained hard even after being boiled for 24 hours. In the early days of pressure cookers, pressures greater than 100 psi were tried. I don’t want anything that high, but it would be nice if I could cook brown rice at 30 psi because that would make it cook faster. It is unclear why we cannot buy pressure cookers that operate at greater than 15 psi. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [October 22, 2015, 1:43am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/30 "2015-10-22T01:43:57Z")
> [@FRE0](#): > > It is unclear why we cannot buy pressure cookers that operate at greater than 15 psi. Really? Have you read this thread? ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [October 22, 2015, 9:23am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/31 "2015-10-22T09:23:44Z")
> [@FRE0](#): > > It is unclear why we cannot buy pressure cookers that operate at greater than 15 psi. While the chef is trying to get thanks, and would be utterly amazed at applause and would die if there was a standing ovation, he is really not interested in \*bringing the roof down \*. ---
**Author:** ![Your\_Great\_Darsh\_Face](https://avatars.discourse-cdn.com/v4/letter/y/ac8455/32.png) [@Your\_Great\_Darsh\_Face](https://boards.straightdope.com/u/Your_Great_Darsh_Face)\ **Post date:** [October 22, 2015, 10:07am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/32 "2015-10-22T10:07:38Z")
> [@Malacandra](#): > > What temperature kills zombification spores, anyway? A higher temperature than we had four years ago, clearly. ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [October 22, 2015, 7:16pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/33 "2015-10-22T19:16:19Z")
The BLEVE link explains “When a liquid boils it turns into a gas. The resulting gas takes up far more space than the liquid did.” For superheated water flashing to steam at atmospheric pressure, that ratio is about 7000:1 That is, 1 cubic foot of superheated water will flash to 7,000 cubic feet of steam. Not fun to be standing next to that reaction. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [October 22, 2015, 7:37pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/34 "2015-10-22T19:37:49Z")
> [@FRE0](#): > > I don’t want anything that high, but it would be nice if I could cook brown rice at 30 psi because that would make it cook faster. My, but you’re an impatient one. My Panasonic rice cooker on quick-mode can ready a batch of brown rice in about 30 minutes. I don’t know how much faster rice could be cooked at 274F (the temp corresponding to 30 psig boiling). Pressure cookers are good for taking hours-long cook times and reducing them to just an hour or two; a pressure cooker that reduces my cook time from 30 minutes to 20 minutes doesn’t add a lot of value. I wonder what [would happen to your cooked rice when you bled off all the pressure at the end of the cook cycle:](https://en.wikipedia.org/wiki/Puffed_rice#Production) > [@Wikipedia](#): > > Another method of puffing rice is “gun puffing”, where the grain is conditioned to the correct level of moisture and pressurised to around 200 PSI. When the pressure is suddenly released, the pressure stored inside the kernel causes it to puff out. This method produces a puffed rice which is spongy in texture. > [@FRE0](#): > > It is unclear why we cannot buy pressure cookers that operate at greater than 15 psi. Heavy (= difficult to use), expensive to make/transport, expensive to insure the manufacturer against product liability suits, and low demand. TL,DR: not profitable. ---
**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\ **Post date:** [October 22, 2015, 8:54pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/35 "2015-10-22T20:54:41Z")
> [@FRE0](#): > > I have unsuccessfully attempted to find a pressure cooker that can be operated at more than 15 psi, perhaps 30 psi. Obviously it would cook faster, but they don’t seem to be available. 30 psi is not especially high; I have an air compressor that goes up to 125 psi and it does not require any special permits. Pressurized water nuclear reactors operate at around 1,500 psi.(snip)It is unclear why we cannot buy pressure cookers that operate at greater than 15 psi. The air compressor is an unfired pressure vessel, while the pressure cooker is fired, it may be that that’s the difference. Vessels with a design temperature less than 210 degrees Fahrenheit are exempt. ASME code Section VIII specifically exempts vessels having an internal or external pressure not exceeding 15 psi (100 kPa). I don’t know why 15 psi was selected rather than 16 or 20, it’s about one atmosphere of pressure, and that may be it. ---
**Author:** ![Earl\_Snake-Hips\_Tucker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/earl_snake-hips_tucker/32/3269_2.png) [@Earl\_Snake-Hips\_Tucker](https://boards.straightdope.com/u/Earl_Snake-Hips_Tucker)\ **Post date:** [October 22, 2015, 10:44pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/36 "2015-10-22T22:44:24Z")
> [@Jinx](#): > > Actually, anything above 15 psig would be considered a pressure vessel by ASME Code and require to be regulated (inspected) under state and/or Federal law. Small vessels receive a “UM” stamp, IIRC, and large vessels over some threshold require a “U” stamp. Also, pressure vessels require a pressure relief valve which has its own cycle of required ASME certified inspections. Oh, and Napier, yes the pressure rating is for a specified temp as temps above the rated temp will weaken the pressure vessel wall material, OK, fess up! Who hacked Jinx’s account? ---
**Author:** ![Flyer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/flyer/32/7298_2.png) [@Flyer](https://boards.straightdope.com/u/Flyer)\ **Post date:** [October 22, 2015, 11:06pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/37 "2015-10-22T23:06:26Z")
> [@Dag\_Otto](#): > > The BLEVE link explains “When a liquid boils it turns into a gas. The resulting gas takes up far more space than the liquid did.” > > For superheated water flashing to steam at atmospheric pressure, that ratio is about 7000:1 > > That is, 1 cubic foot of superheated water will flash to 7,000 cubic feet of steam. Not fun to be standing next to that reaction. That would be one way to steam-clean things. Might not be in usable condition afterward, but hey–nothing’s perfect. ---
**Author:** ![Dag\_Otto](https://avatars.discourse-cdn.com/v4/letter/d/439d5e/32.png) [@Dag\_Otto](https://boards.straightdope.com/u/Dag_Otto)\ **Post date:** [October 23, 2015, 3:17am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/38 "2015-10-23T03:17:33Z")
> [@Earl\_Snake-Hips\_Tucker](#): > > OK, fess up! Who hacked Jinx’s account? I laughed. ---
**Author:** ![Kenm](https://avatars.discourse-cdn.com/v4/letter/k/bc79bd/32.png) [@Kenm](https://boards.straightdope.com/u/Kenm)\ **Post date:** [October 23, 2015, 3:43am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/39 "2015-10-23T03:43:03Z")
> [@AaronX](#): > > My friend managed to open a pressurized pressure cooker once, I heard there was food left on the ceiling. His hand and face got burnt, but he recovered ok (some scars, no loss of function). My mother refused to use a pressure cooker because a friend had been badly hurt by an explosion. I guess my parents were made for each other because my dad wouldn’t screw in a light bulb without making sure the switch was off. A friend of his had a new light bulb blow up in his face. Had that guy not been wearing glasses, he could have been blinded. So I won’t use a pressure cooker and I won’t replace light bulbs (I still have fluorescents for outdoor and basement use) without making sure the switch is off. I think that’s how religions start. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [October 23, 2015, 1:49pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/40 "2015-10-23T13:49:25Z")
> [@Machine\_Elf](#): > > … > I wonder what [would happen to your cooked rice when you bled off all the pressure at the end of the cook cycle:](https://en.wikipedia.org/wiki/Puffed_rice#Production) > > > [@](#): > > > > [excerpt from Wiki cite:]…When the pressure is suddenly released, the pressure stored inside the kernel causes it to puff out… > > … I don’t understand what is meant by “pressure stored,” even though experientially that is as good a way as any to describe it. But it seems kind of just-so-ish. Before I go off to Wiki “compression,”–which is where I think I should go–after which I’ll probably come back anyway, can someone put “storing pressure” into some more discrete terms? Also, I’m guessing here, as well the thermodynamic aspects under discussion here, does the term “continuum mechanics” apply to the area of physics I think I’m getting at? - off to check what c.m. means while he’s there… \* [Previous page](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149.md?page=1) [Next page](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149.md?page=3)