# Why 15 psi max on pressure cookers?
**URL:** https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149
**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:** 1
### Author:  [@kanicbird](https://boards.straightdope.com/u/kanicbird)
#### Post date: [December 30, 2006, 10:20pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/1 "2006-12-30T22:20:14Z")
All the pressure cookers I have seen have 15 PSI as their max pressure, which is the ‘normal’ pressure one would cook with in a pressure cooker. Many have no other setting. The ones that do have other choices usually have 5 PSI as a option.
My questions are:
Why 15 PSI?
Why don’t they make ones that go to 25, or for that matter 90 PSI?
Does anyone make one that exceeded the 15 PSI limit?
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### Author:  [@Rick](https://boards.straightdope.com/u/Rick)
#### Post date: [December 30, 2006, 11:43pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/2 "2006-12-30T23:43:50Z")
I would guess that it has to do with the amount of material that it would take to reinforce it to withstand a higher pressure. For example look at the clamps on this [spray paint tank](http://ads.easyinfo.co.za/htm/custom/toolmart/images/airtools/paint-tank-40l.jpg)
Can imagine the potential danger if a pressure cooker at 90 PSI failed and sprayed shrapnel, and dangerously hot food all over your kitchen? :eek:
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### Author:  [@minor7flat5](https://boards.straightdope.com/u/minor7flat5)
#### Post date: [December 31, 2006, 12:27am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/3 "2006-12-31T00:27:03Z")
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.
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### Author:  [@Napier](https://boards.straightdope.com/u/Napier)
#### Post date: [December 31, 2006, 4:09am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/4 "2006-12-31T04:09:38Z")
I bet it’s historical tradition or lawyers.
Check out Autoclave Engineers in Erie, PA. When I visited them a few years ago they made stock vessels that handled up to 160,000 psi and custom vessels that went higher. I think they managed pretty high temperatures, too.
I remember working out one time conditions that made supercritical water miscible with silica.
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### Author:  [@casdave](https://boards.straightdope.com/u/casdave)
#### Post date: [December 31, 2006, 12:24pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/5 "2006-12-31T12:24:25Z")
I would expect that you’ll find that above a certain pressure (and also a certain volume), it would come under pressure vessel legislation, which requires regular maintenance inpections, such as safety valve testing and overpressure tests.
Differant countries have differant requirements, but when you take into account manufacturing tolerances, and the general srewup factor, the potential safety margin pressures might mean that although 15 p.s.i is hugely under the limits, this other factors might push it somewhat closer.
According to _[Wikipeadia_
The pressure was set by USDA way back in 1917, probably under the _Food control and production acts_
> **[Pressure cooking](https://en.wikipedia.org/wiki/Pressure_cooker)**
>
> Pressure cooking is the process of cooking food under high pressure steam and water or a water-based cooking liquid, in a sealed vessel known as a pressure cooker. High pressure limits boiling and creates higher cooking temperatures which cook food far more quickly than at normal pressure.
> The pressure cooker was invented in the seventeenth century by the physicist Denis Papin. It works by expelling air from the vessel and trapping steam produced from the boiling liquid. This is used to raise th...
In the UK pressure vessels means anything above around 7 p.s.i with a volume greater than 250 bar litres, but as the pressure goes up, the allowable volume decreases.
[http://www.devonline.gov.uk/text/index/information\_and\_services/environmental\_health/eh-healthandsafety-intro/eh-hs-guidance/eh-hs-pressuresys.htm](http://www.devonline.gov.uk/text/index/information_and_services/environmental_health/eh-healthandsafety-intro/eh-hs-guidance/eh-hs-pressuresys.htm)
I would expect that to construct a pressure cooker that fell into these classifications would result in something prohibitively expensive, and realistically it not actually worth it in terms of pratical use, higher pressure+higher temperature with the accompanying risks of safe venting.
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### Author:  [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)
#### Post date: [December 31, 2006, 2:46pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/6 "2006-12-31T14:46:09Z")
It looks like this question calls for factual answers rather than opinions, so I’m moving this thread from IMHO to General Questions.
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### Author:  [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)
#### Post date: [December 31, 2006, 3:17pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/7 "2006-12-31T15:17:03Z")
I believe casdav has the reason that higher pressure ones are not in most retail stores. You would have to have regular inspections all the stuff that goes with it. When a high pressure vessel explodes everybody can end up dead.
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### Author:  [@rowrrbazzle](https://boards.straightdope.com/u/rowrrbazzle)
#### Post date: [December 31, 2006, 9:51pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/8 "2006-12-31T21:51:15Z")
[QUOTE=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.
[/QUOTE]
Home canning was once widely practiced. According to this page [HealthLink BC - 24/7 Health Advice You Can Trust](http://www.bchealthguide.org/healthfiles/hfile22.stm) 240F is the minimum temperature to destroy botulism spores, reached at 10psig. It’s necessary when canning low acid foods like meat and most vegetables. This page [http://muextension.missouri.edu/xplor/hesguide/foodnut/gh1490.htm](http://muextension.missouri.edu/xplor/hesguide/foodnut/gh1490.htm) has a chart that says to use 15psig for weighted gauge pressure cookers for altitudes 1000-2000 feet.
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### Author:  [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)
#### Post date: [January 2, 2007, 4:10am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/9 "2007-01-02T04:10:03Z")
[QUOTE=kanicbird]
Why 15 PSI?
[/QUOTE]
To answer this specifically:
Because there is no consumer demand for anything more than 15psi.
- all the recipes out there are designed for 5, 10, or at most 15psi.
- all the cooks out there have experience using these psi’s.
- food cooks quickly at 15psi, without significant damage to flavor or texture. Higher psi’s would tend to result in mush-like food.
- more than 15psi would require a sturdier cooker, thus more expensive.
- more than 15psi would be riskier, thus more expensive product liability insurance.
- more than 15 psi would be more expensive to use; you have to heat it up to a higher psi, all that is lost when you open it to take out a set of jars, then you have to get it back up to that high psi again for the next load.
So basically, a max of 15psi is what everybody’s used to using, and it’s **good enough** to do the job.
Such info is one of the benefits of having a mother who has done home canning all her life. And still is doing so in her mid-80’s. For Xmas, I received a box of home canned items, mostly grown in her home garden.
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### Author:  [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)
#### Post date: [January 2, 2007, 8:24am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/10 "2007-01-02T08:24:50Z")
[QUOTE=casdave]
I would expect that you’ll find that above a certain pressure (and also a certain volume), it would come under pressure vessel legislation, which requires regular maintenance inpections, such as safety valve testing and overpressure tests.
[/QUOTE]
Maybe, but I have an air compressor that goes to 150 psi for which I don’t need regular inspections. Government safey regulations don’t seem to apply as long as the public and any employees are not involved with the compressor.
As a complete WAG I would go along with **minor7flat5** and **[t-bonham@scc.net](mailto:t-bonham@scc.net)** that 15 psi gets you to as high a boiling point as is needed or desirable for cooking purposes.
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### Author:  [@SuperNelson](https://boards.straightdope.com/u/SuperNelson)
#### Post date: [January 2, 2007, 1:57pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/11 "2007-01-02T13:57:20Z")
Is there any relationship between 15 PSI in the pressure cooker, and 15 PSI being the ambient pressure at sea level? I would guess that the pressure cooker value is relative pressure, but is there a particular significance to the pressure inside the cooker being roughly double the pressure outside?
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### Author:  [@Napier](https://boards.straightdope.com/u/Napier)
#### Post date: [January 2, 2007, 5:08pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/12 "2007-01-02T17:08:29Z")
\>Is there any relationship between 15 PSI in the pressure cooker, and 15 PSI being the ambient pressure at sea level?
Good question, and this seems oddly significant, but I can’t think of any relationship at all. Temperatures depend in a nonlinear way on pressures so it’s not like this should let you cut cooking times exactly in half, easier to calculate. Nothing special happens at 15psig = 30 psia to my knowledge. I do a lot of work in thermodynamics, but nothing looks important about this pressure to me.
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### Author:  [@casdave](https://boards.straightdope.com/u/casdave)
#### Post date: [January 2, 2007, 5:48pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/13 "2007-01-02T17:48:42Z")
The UK pressure vessel regulations certainly cover compressed air vessels, however here we are dealing with steam, which has the added ingredient of temperature.
Pressurised air vessels would still require safety valves, and above a certain volume and pressure, would certainly require testing.
Control of pressure could also be achieved by ensuring that the pump could not supply above a certain limit.
I can think of plenty of applications where fairly small steam pressure vessels come under the regulations, things such as instrument autoclaves, the total volume of some of these isn’t a huge leap from that of a large pressure cooker.
Some industrial cooking systems also fall under the regulations, so all in all, it isn’t too great a stretch.
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### Author:  [@wilderkind](https://boards.straightdope.com/u/wilderkind)
#### Post date: [September 28, 2011, 8:13pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/14 "2011-09-28T20:13:18Z")
AMSE code states that any vessel exceeding 15 psig must be inspected periodically for safety reasons. This law is inacted to regulate boilers primarily.
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### Author:  [@Folacin](https://boards.straightdope.com/u/Folacin)
#### Post date: [September 28, 2011, 8:18pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/15 "2011-09-28T20:18:53Z")
> [@wilderkind](#):
>
> AMSE code states that any vessel exceeding 15 psig must be inspected periodically for safety reasons. This law is inacted to regulate boilers primarily.
But I wonder if that level was set because most pressure cookers are 15 psi? Possibly a chicken/egg sort of thing?
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### Author:  [@Malacandra](https://boards.straightdope.com/u/Malacandra)
#### Post date: [September 28, 2011, 8:24pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/16 "2011-09-28T20:24:16Z")
What temperature kills zombification spores, anyway?
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### Author:  [@Rocketeer](https://boards.straightdope.com/u/Rocketeer)
#### Post date: [September 28, 2011, 9:16pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/17 "2011-09-28T21:16:55Z")
> [@David\_Simmons](#):
>
> Maybe, but I have an air compressor that goes to 150 psi for which I don’t need regular inspections. Government safey regulations don’t seem to apply as long as the public and any employees are not involved with the compressor…
Your air compressor isn’t full of superheated steam, either. A steam explosion is much much worse than a compressed-gas explosion.
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### Author:  [@Jinx](https://boards.straightdope.com/u/Jinx)
#### Post date: [September 28, 2011, 11:36pm UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/18 "2011-09-28T23:36:05Z")
> [@Napier](#):
>
> I bet it’s historical tradition or lawyers.
>
> Check out Autoclave Engineers in Erie, PA. When I visited them a few years ago they made stock vessels that handled up to 160,000 psi and custom vessels that went higher. I think they managed pretty high temperatures, too.
>
> I remember working out one time conditions that made supercritical water miscible with silica.
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,
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### Author:  [@drachillix](https://boards.straightdope.com/u/drachillix)
#### Post date: [September 29, 2011, 12:42am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/19 "2011-09-29T00:42:54Z")
> [@Rocketeer](#):
>
> Your air compressor isn’t full of superheated steam, either. A steam explosion is much much worse than a compressed-gas explosion.
Sure…until you have a tank of chlorine gas go…
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### Author:  [@AaronX](https://boards.straightdope.com/u/AaronX)
#### Post date: [September 29, 2011, 2:22am UTC](https://boards.straightdope.com/t/why-15-psi-max-on-pressure-cookers/386149/20 "2011-09-29T02:22:50Z")
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).
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