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What are “standard” and “non-standard” pressure cookers?

common pressure cooker high and low pressure settingsTo facilitate the writing of pressure cooker cookbooks and sharing recipes, there is an un-official standard.  This standard includes the maximum operating pressure for American Pressure Cookers (15 psi)  and the maximum operating pressure for most modern European Cookers (which is about 13 psi for spring-valve type cookers).

Any pressure cooker that does not fall within this range  – or used in a high-altitude situation (see below) – is “non-standard.”

There is no international pressure cooker  organization that sets a global standard.  Pressure cooker UL Rating, which is an American Appliance Testing standard, only states that a domestic pressure cooker “operate at a nominal pressure of 15 psi (103 kPa) or less.” While in Europe the CE rating, the equivalent to the American certification, state that a “simple pressure vessel” can be above .5 bar (7.2 psi) and below 50 bar (720 PSI) . American manufactured pressure cookers adhere to a standard for pressure canners set by USDA in 1917 – 15 psi.

While some European pressure cookers are sold world-wide many of these manufacturers make a separate model specifically for the American market that reaches 15 psi.  Some European manufacturers are switching to a single model distributed world-wide that reaches 15 psi. At the writing of this article,  American pressure cooker manufacturers only sell their pressure cookers in the United States.

How do “non-standard” pressure cookers affect cooking time?

pressure cooker time adjustmentsThere is no set rule or formula. Pressure cooking time really depends on the size and density of the food. Most refined grains and quick-cooking vegetables do not need pressure cooking time adjustments, while tough legumes, whole grains and thick roasts will need several minutes more cooking time. In other words, the denser or larger the food, the more time a cooker operating at a lower pressure (thus lower temperature) will need to achieve the same results as a standard cooker.

All recipes and cooking time charts on this website are written to accommodate both “standard” and “non-standard” pressure cookers.  When necessary,  times are written in a range – standard pressure cookers should use the shorter cooking time (13 minutes) and non-standard pressure cookers the longer (20 minutes).

More Info: Pressure Cooking Times for standard and non-standard pressure cookers

Do all pressure cookers actually reach 15 psi?  

This comes down to the difference in measuring systems between the United States (imperial) and the rest of the world (metric).  Pressure in the rest of the world is measured  in kilopascals (kPa) and bars while the U.S.it is measured with pounds per square inch (psi).

European manufactured pressure cookers are designed to cook at 1 bar or 100 kpa (metric pressure measurements) and that translates to 14.5 psi (this is rounded up to 15 psi) but American manufactured pressure cookers are designed to reach a full 15 psi (see below, for information on electric pressure cookers).

How does an increase of pressure affect the cooking temperature?

The rise in pressure inside the pressure cooker directly correlates to the rise in boiling point – the maximum cooking temperature that can be achieved at a given pressure.

pressure cooker temperature per peressure

Using the Antoine Equation we  also produced more detailed charts. 

More Info: Pressure and Boiling Points of Water – The Engineering ToolBox
More Info: Water Vapor Pressure and Boiling Points (Antoine Equation)

How are pressure cooking times affected by “high altitudes”? Isn’t atmospheric pressure already 15 psi?

The pressure cooker adds pressure above the current atmospheric pressure. Since there is a pressure difference in the atmosphere between one altitude and another, the pressure cooker’s pressure will vary accordingly.

atmospheric pressure by altitudeAt sea level, the atmospheric pressure averages 14.7 psi – add 15 psi of pressure generated by the pressure cooker and the food in the cooker is cooking at 29.7 psi of absolute pressure.

Moving up in the atmosphere, or going to higher altitude, the atmospheric pressure decreases.  So in Denver Colorado (about 5,000 feet) the atmospheric pressure averages only 12.2 psi- add 15 psi of pressure generated by the cooker and there the food is cooking at just 27.2 psi of absolute pressure -almost 3 psi less pressure than pressure cooking at sea level!

No matter where you are, a pressure cooker will always add pressure to the current atmospheric pressure.

The same 15 psi pressure cooker will cook 15 psi in San Francisco, California (sea level) but only 12.5 psi in Denver, Colorado (5,000 feet).  Now, “standard pressure cooker” has become “non-standard” in Denver.  This means that the recipes will need the same timing adjustments used  for non-standard pressure cookers (see pie chart, above).

adjusted cooking pressure by altitude

formula to adjust high-altitude pressure cooking times

Increase pressure cooking time by 5% for every 1000 ft above 2000 ft elevation (see table, below). Multiply the recommended cooking time by the number on the table. The result will likely be a decimal value just round that up to the next minute.

above...increase by..or multiply by..
3,000 feet5%1.05
4,000 feet10%1.1
5,000 feet15%1.15
6,000 feet20%1.2
7,000 feet25%1.25
8,000 feet30%1.3
9,000 feet35%1.35
10,000 feet40%1.4

More Info:  Air Pressure and Altitude Above Sea Level – The Engineering ToolBox

Why do American, European and Asian pressure cookers all reach different pressures?

presto war effort vintage ad
“The manufacturing facilities of the makers of PRESTO COOKERS are now devoted to war production. Once victory is won – there will be Presto Cookers for everybody. Until then, if you own one, share it, won’t you? It’s a good neighbor policy.”

The transformation from a Renaissance “bone digester” invented by French scientist Denis Papin (in 1689) to pressure canners (1905)  and finally to the pressure cooker we know today began in 1926. The Home Exhibition in Paris introduced the first model for home use. The pressure cooker made it out of Europe and into the United States via the 1939 New York Fair where the National Pressure Cooker Company launched the first U.S. model.

Aluminum pressure cookers took off in the U.S. and many companies began producing them. Then, America’s involvement in WWII halted the production of pressure cookers and their factories were dedicated to producing munitions for the overseas war.

Once the war ended, European and American pressure cooker manufacturers began to develop and produce pressure cookers independently from each other. While in America unscrupulous factories made and sold sub-standard pressure cookers – that eventually went on to mar the cooker’s reputation and halt innovation- European manufactures continued to develop, perfect and innovate their designs adding multiple redundant safety mechanisms, selectable pressure levels and more features.

The 90’s started the trickle of European manufactured pressure cookers, and their features into America. It’s also when the patent for the first electric pressure cooker was filed by Chinese scientist, Mr. Yong Guang Wang.  The electric pressure cooker was developed independently from stovetop pressure cookers in that they were based on the ever-popular electric rice cookers (hence the resemblance) and are manufactured in a range of pressures – depending on the manufacturer or design team.

Is there an electric pressure cooker that cooks 15 psi?

At the time of the writing of this article, most electric pressure cookers reach 15 psi but they do not cook at 15 psi.  As illustrated by the graphic below – electric pressure cookers reach 15 psi briefly during the warming process.

Electric pressure cookers build pressure up to 15 psi but then maintain a lower pressure during the cooking.  In the  graph below the “operating pressure” is 11.6 even though the cooker reaches 15 psi while it’s building pressure. “Operating Pressure” is the true pressure at which an electric pressure cooker cooks.

electric pressure cooker heat cycles

More Info: How Electric Pressure Cookers Work – Instant Pot

How can I find out what pressure my pressure cooker reaches?

Most instruction booklets have this information written in them. The number may be written in kPa, bar or PSI (use the table in this page to decode the approximate PSI).  There may be several terms used in conjunction with those numbers and they include:

  • Operating Pressure –  the pressure at which the pressure cooker cooks the food.
  • Valve Release Pressure – the pressure at which the main regulating valve releases pressure (2 to 4 psi more than the operating pressure depending on the manufacturer).
  • Warping Pressure – the pressure at which the base or components of the pressure cooker deform.
close-up of Instant Pot pressure valve
Instant Pot pressure valve with “105kp” (15.2 psi) valve release pressure. But the “Operating Pressure” at which this cooker cooks food is 11.6 psi.

Stove top pressure cookers may also have this information written on the base, and the maximum valve release may be written on or near the valve.

Electric pressure cookers will have the “valve release pressure” written in very small text on the underside of the pressure release valve either on the plastic housing, or the metal part of the valve.

More Info: Free Pressure Cooker Manual Library

More Questions?
Leave a comment below, and we’ll do our best to find the answer.

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92 Comments

  1. I greatly enjoyed this article; it’s the best that I have ever read on this topic. The comments are also very informative.

    I watched the ATK PC review a year or so ago and felt that there was something inherently wrong with it, but didn’t know enough to say exactly what it was. So thanks for clarifying what went wrong there. I find it enlightening that they are using commercial, rather than regular domestic, ranges.

    I do see one very minor typo under “Why do American, European and Asian pressure cookers all reach different pressures?” I think that “The transformation form” should be “The transformation from”?

    Again thanks for such an excellent article.

    Bev in TX

    1. Welcome Bev, I’m so glad to read you found this article informative! I corrected the type-o, you were right it should have been “from” thanks for letting me know.

      Ciao,

      L

  2. Very helpful article, thank you. I am still using my classic Presto I have had for 35 years, with the rocking weight,(charmingly damaged by my now 42 year old son, when he dropped it in the disposal when he was 13). However, I decided to add an electric pressure cooker for more versatility, and I got confused by all the references to PSI. I moved from a low altitude to Denver recently, and the boiling point of water here is 203. High altitude is a challenge. I had to start using a rice cooker to get fully cooked rice. Thank you for the reliable reviews. BTW, you should have seen the pressure cooker contraption I had when I lived in Romania…so complicated!

    1. Are you able to safely can fruits and vegetables at this altitude?

  3. Excellent article. I am researching various stovetop pressure cookers and am having trouble finding out the EXACT cooking pressure for the various models.

    But I would like to know if it makes a lot of difference? I grew up with the classic SEB stovetop pressure cookers from the 1970’s in France and would like one that gives a similar performance. However I am not able to discover exactly what pressure the SEBs operated at. I am wondering if a 11.6/12 psi operating model would require significantly longer cooking times than a 14.5/15 psi operating model?

    1. Welcome, Marcus! Take a look at our cooking chart (which also notes the PSI) to see the timing difference between the two pressure cooker types. Most likely, your old SEB operated at the same pressure as modern electrics. : )

      https://www.hippressurecooking.com/pressure-cooking-times/

      Ciao,

      L

  4. I am now in a position to add some information and opinions for the benefit of your subscribers. After a lot of research, I found out that the pressure cooker I had been using for several years (Arcosteel 5.5 litre, now discontinued) had a cooking pressure of 14 psi. I found that it cooked meals extremely fast, and was happy with it; however I was eventually forced to abandon it because the seal was failing and, since the product has been discontinued for many years, replacement seals were no longer available.

    Eventually I decided to buy the 6-litre Tefal Secure Neo 5 pressure cooker. The technical department informed me it had a cooking pressure of 12 psi (and a lower setting of 7 psi). I have experimented with it and found the following:

    1) The lower pressure (12 psi vs 14 psi) means I need to cook meats for an average of 3 minutes longer (chuck steak cut into pieces: 18 minutes compared with 15 minutes for the Arcosteel).

    2) The lower pressure means that the steel is thinner, which means that the cooker heats up much faster (both for browning meats and to reach pressure).

    3) The lower pressure means it releases pressure much faster.

    4) The lower pressure means that the vegetables come out a lot less mushy, and the meat comes out tastier.

    So, as you can see, on the downside the lower pressure results in a marginally higher cooking time, which is more than offset by the shorter heating and depressurizing times, and the better food quality.

    The only negative aspect of the Tefal cooker concerns the steam release valve. It ejects a constant jet of steam, which makes it a little difficult to gauge when it is just “simmering” (other models have metal valves which wobble or spin to signify adequate pressure); and the steam is ejected vertically upwards, which means you have to be a little bit careful reaching your hand directly over it, as you may get scalded (other models eject steam sideways, which is less hazardous).

    (I never managed to find out the operating pressure of the original SEB cookers which I used in France; someone told me they operated at 8 psi, but I find it hard to believe that they operated at such a low pressure.)

    1. Marcus, thanks for sharing your experience – very interesting and accurate observations. Except for one (though it could have been a mis-type):
      “2) The lower pressure means that the steel is thinner, which means that the cooker heats up much faster (both for browning meats and to reach pressure).”

      The steel does not get thinner, but it is true that since the cooker needs to reach a lower temperature it takes less time to reach it. : )

      Ciao,

      L

  5. Laura, maybe I didn’t make myself clear, sorry. What I meant was:

    “2) The lower pressure means that the steel does not have to be as thick as with higher pressures, and thinner steel allows the cooker to heat up faster (both for browning meats and to reach pressure).”

    Admittedly the thinner metal may not have a large influence on the rate of heating up once the cooker is closed, but it definitely has an influence on initial heating time for browning meats.

    And it is a fact that my Arcosteel cooker is noticeably heavier (due to thicker metal) than my Tefal cooker, despite the fact that the Tefal cooker has a slightly larger capacity.

    Cheers, Marcus

  6. one thing i noted on reading many reviews was that those that were replacing an old weighted type ally ps with a stainless ps all seemed to be saying that the new ss was lighter (for the same capacity) and faster to reach pressure but tended to burn stuff to some degree.
    stainless steel is actually heavier than ally so the weight loss has to be it’s higher strength allowing thinner material, which would of course heat up faster (locally) but stainless is a poor thermal conductor compared to ally and is known to develop hot spots because of this.
    if you look at the high end stainless pots n pans you will find they have usually a copper base this is to overcome the hotspots and poor thermal conductivity, any thin material will develop hot spots but coupled with poor thermal conductivity makes it worse.

    one of the electrics claims to have a multi layer base on their stainless inner pot which is probably to address this, i think it was the instant pot duo that claimed a 3ply base on the inner stainless pot.

    so perhaps reducing the initial heat input would help to stop the burning although it would slow the getting to pressure, i dont have any experience to offer but thought i would post this as a possible cure, i’m sure laura will have a better idea than me whether or not it would help.
    though this is similar to her advice on using induction as a heat source.

    for those that are a bit concerned about all the safety hype over pressure cookers.
    if you drive a car or travel in one you’ve been riding with a pressure cooker, how was it?
    i have always thought the cooling system was at 4-8 psi but it seems it’s higher, according to superstreetonline.com factory caps are at 14-15 psi, so around the same as your pressure cooker!

    if laura doesn’t mind i’ll add the link to the page discussing engine cooling,
    http://www.superstreetonline.com/how-to/engine/61718-cooling-systems/

    this link helps to understand the differences between ally and stainless, and supports what i said above.

    1. Ian, I don’t know about gas or diesel engines, but the pistons on steam engines – the very ones that sparked the Industrial Revolution with trains and factories – were actually designed from the first pressure cooker valve. : )

      All stainless steel pressure cookers have an aluminum disk fused to the bottom to distribute heat evenly. Stove top manufacturers have always boasted on the thickness or width of this disk. I’ve never been able to get a straight answer from Instant Pot about the thickness or width of theirs. I don’t doubt it’s there, but I probably think it is just a minimal token amount based on my experience in browning on high-quality stove top vs. the Instant Pot with stainless steel insert – the main “heat distribution” in electric pressure cookers comes for the base-wide ceramic heat disk.

      Ciao,

      L

  7. laura
    i wasn’t aware of the historical association between pressure cookers and steam engines, something i’ll have to investigate, thanks for the info, as a child i had a couple of steam engine models so always been interested in them.
    i thought that aluminum/aluminium (the main reason for using ally:)) was also used but couldn’t be bothered to check.
    the ip duo inner was said to not be suitable for induction perhaps this was due to a potential for damaging the the fusing of the two? or perhaps the type of stainless used is non magnetic as some stainless is, i suspect the former as it could mean the stainless expanding before the aluminum.
    the information on the thickness may be licenced so the manufacturer may not be able to give details.
    as they state 3 ply the aluminum may just be the filling in a stainless sandwich a method used in some products.
    this would make sense given the hype about aluminum as it would be sealed in so not able to contaminate your food, not so important to a stovetop as an inner pot.
    my post was more in relation to stovetop than electric, as i see it the only real advantage of electric is push the button and walk away, power cuts permitting:-)
    although given the demands on time now, it can be a major advantage!

  8. At 8200′, I greatly appreciate the research and information. +35% it is, but still better than regular cooking!

  9. Laura,

    If cooking times are increased for elevation (lower ambient pressure at elevation, and thus a lower cooking temperature), then how do we adjust cooking times for an electric pressure cooker that cooks at 9 PSI (e.g, the new Fagor 360) or 11 PSI (e.g, the Instant Pot Duo Plus). It seems that most recipes that I have are designed around a 15 PSI conventional cooker? Concerns about safe cooking are preventing me from purchasing an electric pressure cooker. I emailed Fagor and Instant Pot, and have yet to hear back…Thoughts?

    1. Use the elevations charts “backwards”. Find your pressure in the chart and use that as your “altitiude” for adjusting timing. If you really live at altitude, add in the real altitude then use the new combined altitude for your timing corrections.

      Other ideas:
      Use Laura’s recipes. She gives timing for both stovetop and electrics.
      Get the Breville Fast Slow Pro. It has an altitude correction built in for its preprogrammed settings

  10. Thank you. I did order Laura’s book. I am not sure that the reverse altitude calculation works. If I go to the calculator: https://www.mide.com/pages/air-pressure-at-altitude-calculator and put in a sea level pressure of 14.7 psi, and a (weather) temperature of 70 degrees…then an air pressure of 8.7 psi (15 of standard minus 9 of Fagor = 6, and 14.7-6 equals 8.7), then the altitude would be 14,106 feet. If the rule is 5% for every 1000 feet above sea level, well…cooking time would increase by I think way too much (70%). I also get the feeling that the heat up and cool down time would lead to things being further overcooked. So the equation isn’t linear. Now, I could break down and do a PV=nRT calculation (haha remember that), but following Laura’s book seems easier to me for now.

    1. Kayla, what Fagor model do you have? I’m no aware of any of their stovetops going under 15 psi or any of their electrics going under 11 psi.

      Ciao,

      L

      1. Laura,
        From the Fagor Lux manual ( I couldn’t find the 360/LCD manual):
        “HIGH-Use this function to cook at high pressure, 9 psi (pounds per square inch)”

        However, it also says
        “High Pressure 240°F-248°F”
        Which from your charts above would roughly equate to 10…14psi.

        Have you tested one of their electrics to find which is true?

        Kayla,
        1. The formula you cite proves the relationship is linear. It says for a given volume, Pressure is proportional to temperature.

        2. Pressure cooking is inherently safer than “normal” cooking at ANY pressure. This is because it is cooking at higher than boiling point for any given altitude. For a given time, more bugs will be killed. If you are comparing Electrics to Stovetops, then to achieve the same bug kill rate, you will need to increase the cooking time. But cooking is not about killing bugs. It is about making food more appetising. Safe cooking is about the entire workflow. Not just the temperature the food reaches. If you 7D sterilise a piece of meat, then cut it with a dirty knife, it will probably be less safe than a piece of raw meat cut with a clean knife. Something every good Sashimi chef knows.

        1. Well, I suspect that’s an error or extreme modesty.

          I’ve used both the LUX and LUX LCD using normal “electric” pressure cooking times and have not noticed anything under-cooked. The spring valve on their lids appear to be the same they use on stovetop pressure cookers. I don’t have the equipment to calibrate a spring but it is the exact same size, height, width and thickness as the spring used for their 15psi stovetop pressure cookers. So there is an expectation that when it initially builds and reaches pressure, just like all electrics, it will at least go over 15psi (I think the stovetop spring is actually calibrated at about 17psi). Comparatively, the weight on the Instant Pot says it is 105kpa which is equivalent to 15psi.

          Since all electric cookers operate at a range of pressure – and most report the higher number in the range – it could just be that Fagor is reporting the lower number.

          I will measure the internal temperature when I review the cookers but at this point, I have not noticed any difference between the Fagor Electrics and Breville’s Fast Slow Pro or Instant Pot in terms of “high pressure” cooking temperatures.

          I think the Fagor LUX valve is superior to all other electrics because it is the NEXT generation technology (that stovetops have been using for decades). In fact, all the LUXes reach pressure in half the time and just need 1/2 cup of liquid to reach and maintain pressure compared to other electrics that I’ve personally used (and likely on the market, too).

          Ciao,

          L

          1. It is great that Fagor are using spring valve technology. Now all they need to do is add a PID controller (as used in Sous Vide appliances) in place of the thermostat to get precision control of temperature. Now that would be an Electric to buy.

  11. Good points, Greg and thank you. I do think that for now I will just use Laura’s book to guide me. The gas formula as written is linear, but the real deal is that cook cool down and warm up time messes up that neat linear equation. Full disclosure is that I recently had a worm infection from undercooked meat and thus am gun shy about killing bugs. I do also think that for some items, I still like dry cooking methods and an instant read thermometer. Over and out for now!

  12. Living at 7.000 feet, I’ve found this article extremely helpful. I love my instant pot, but it’s shocking to know it’s only doing 7.5psi up here. Even with the plethora of stovetop 15 pound canners, I can’t reach safe temperatures for low acid foods. Do you know off any that come with 20lb weights, or more? Google and Amazon have been very unhelpful. Thank you in advance!

    1. Hi Robyn, look into the All American pressure canners – their pressure gauges go up to 30psi. Make sure to get it calibrated before each canning season at your local extension. Also, take a look at all the links that I have at the bottom of this article – including the USDA Complete Guide to Canning (which has adjustments for canning up to 8,000 feet in altitude).
      https://www.hippressurecooking.com/pressure-canning-faq-put-em-up/

      Ciao,

      L

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