Trial Magazine

Physicist Denis Papin invented the pressure cooker in the 17th century.¹ With the introduction of the “Flex-Seal Speed Cooker” in 1938, and the “Presto” pressure cooker in 1939, pressure cookers quickly became common in the family kitchen.²

In those early days of pressure cookers, no published safety regulations applied to them. As a result, sometimes the pressure cooker was opened by a consumer who believed that the pressure had been released—or worse, the pressure cooker exploded like a bomb. These events could and did cause serious, sometimes fatal, injuries to anyone nearby.

Copyright © Claxtonphotography/Getty Images.

Recently, electric pressure cookers with a self-contained electric heating element and programmable cooking cycles have become popular kitchen appliances. Modern electric pressure cookers, if properly designed and manufactured, should not explode or open under pressure and cause injuries.

However, many of these modern pressure cookers have caused injuries when the lid opens while the pot is under pressure.³ Sometimes the lid explodes off the pressure cooker spontaneously.⁴ In other instances, the pressure cooker is in the process of being opened by consumers who believe that pressure has been released—however, as they begin to rotate the lid it suddenly blows off, and the scalding contents erupt out of the pot.

As consumers continue to be injured, some pressure cookers have been recalled,⁵ and some have been the subject of successful class actions related to their defects.⁶ If you seek to represent a client injured by a defective pressure cooker, you must understand how these products operate, the applicable standards, potential jurisdiction challenges, and what to seek in discovery.

Pressure Cooker Basics

How a pressure cooker works is basic high school physics: At the atmospheric pressure of sea level, water boils at 100°C (212°F), but when under pressure it boils at a higher temperature. For example, at 30 pounds per square inch (psi), or 2 standard atmosphere (atm), water boils at 121°C (250°F). When water reaches its boiling temperature, it instantly changes from a liquid to a gas (steam).

No matter how high you turn up the flame on a stove burner, the water in an open pot of water will never heat to more than the temperature at which water boils, because once it reaches that temperature, it instantly becomes steam. In a pressure cooker, liquid is “super-heated” to above its boiling temperature. Solids boiled in a pressure cooker versus in an open pot of water heat to a much higher temperature as well.⁷

If the lid of the pressure cooker is opened while the contents are still under pressure, suddenly the pressure in the pot is reduced to the room’s atmospheric pressure. The compressed gas—the steam—is quickly released. Additionally, all the super-heated water in the pot suddenly becomes steam. That instant conversion from liquid to gas is literally an explosion. Because the solids in the pressure cooker contained water in them, they are blown apart as the water in them instantly converts to steam, and the super-heated contents of the pot erupt out of it.

When a pressure cooker explodes, anyone nearby may be scalded by steam and sprayed with super-heated solids, which stick to their face, arms, chest, and legs, causing second-degree, and often third-degree, burns. The solids are hot enough to burn through clothing.

Safety Requirements & Industry Standards

People are injured by pressure cookers because the product either was not designed or not manufactured to perform over time in compliance with the required safety standards. All pressure cookers should be designed to not over-pressurize to the point of the lid blowing off or the pot exploding.

Older pressure cookers had a vent valve on the lid and a weight that fit on that vent valve to seal it. Eventually the pressure rises to the point of lifting the weight, venting the pot and preventing the lid from blowing off or the pot exploding.

Modern pressure cookers, both stovetop and electric, do not have a weight on the lid but instead have a mechanical pressure-sensitive vent valve. If the pressure reaches a certain level, the vent valve opens, releasing pressure and preventing the pressure cooker from over-pressurizing to the point of blowing off the lid or exploding. However, if that vent valve is defective or becomes blocked or clogged, there is a risk of over-pressurizing.

Modern pressure cookers must have two basic safety features. First, they must be designed and manufactured so they will not build up so much pressure that the lid blows off or the pressure cooker pot itself explodes. Second, they must be designed and manufactured so that if the pot is pressurized it cannot be opened until the pressure has dissipated—equalized with the atmospheric pressure of the room.

Modern pressure cookers typically have a locking mechanism built into the lid that prevents it from being opened while there is pressure in the pot. (See Figure 2.) The lid, once on the pot, is rotated to the pressure cooking position, and flanges on the lid and the pot prevent the lid from being lifted off the pot. Then as the pressure builds in the pot, a device called a “float valve” rises and seals a vent on the lid of the pot. The float valve remains in the “up” position as long as the pot is pressurized. When the float valve is in the up position, the lid cannot be rotated to the open position.

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However, due to the inadequate design of the lid locking components, or manufacturing variations, some pressure cooker lids can be rotated to the open position while the pot is under pressure. When this happens, as the flanges on the lid-pot interface disengage, the lid suddenly blows off the pot, and the super-heated contents erupt out of the pot.

Standards in the industry (generally accepted practice) and published standards both apply to these products. Specifically, two UL standards are on point for pressure cookers.⁸ However, UL standards are voluntary. They are not mandatory consumer product safety standards. They have neither the force of law nor are they entitled to the presumption of validity that would be accorded administrative regulations.⁹ Nonetheless, in my experience, experts writing reports and testifying—for both injured consumers and manufacturers—cite applicable UL standards as a statement of what is the generally accepted standard in the industry.

UL 1026 Standard for Safety: Household Electric Cooking and Food Serving Appliances. UL 1026 sets forth general safety standards for “household electric cooking and food serving appliances.” It does not address pressure cookers specifically, nor does it address safety issues related to the opening of pressurized vessels. UL 1026 also does not appear to apply to stovetop kitchen products, such as stovetop pressure cookers. However, as electrically self-powered pressure cookers are the subject of a significant amount of recent pressure cooker litigation, UL 1026’s general safety standards are often still relevant.

UL 136 Standard for Safety: Pressure Cookers. UL 136 is on point when it comes to pressure cooker safety. Section 9 directly addresses the issue of lid locking safety, requiring that when under pressure, the lid of a pressure cooker must not be able to be opened with less than 100 pounds of rotational force. It also requires that when the lid is opened, there is no eruption of the scalding contents out of the pot. All pressure cookers must be designed to meet this standard—and in fact, most do meet it.

However, UL 136 states in its Introduction, 1.1:

These requirements cover household-type cooking utensils known as pressure cookers or pressure sauce pans which operate at a nominal pressure of 15 psig (103 kPa) or less. They are intended for use over gas- or electric-top burners of residential-type cooking ranges.

For this reason, UL 136 arguably does not apply to self-powered electric pressure cookers. However, whether it applies by the express language of the standard or not, it is still on point because it’s the industry standard. Some major manufacturers of electric pressure cookers test and certify their electric pressure cookers to meet the requirements of UL 136. I have found in discovery for my cases that Section 9, for instance, is used for the certification of some electric pressure cooker appliances.

If UL 136 does not apply to electrically self-powered pressure cookers, why do some manufacturers have their pressure cookers tested and certified by UL as complying with UL 136? One interpretation is that the introduction to UL 136 was intended to make it clear that even though they are not electrical appliances, UL 136 is intended to also apply to stovetop pressure cookers.

Further, if UL 136 does not apply to self-powered electric pressure cooker products, then there is no applicable UL standard for electrically self-powered pressure cooker lids. That does not make sense.

All pressure cookers should be designed to not over-pressurize to the point of the lid blowing off or the pot exploding.

Standards in the industry. Experts that I work with tell me that regardless of whether the UL 136 expressly applies to electrically self-powered pressure cookers, the standard in the industry is that electrically self-powered pressure cookers need to be as safe and comply with the same industry safety standards as stovetop pressure cookers. The industry standard is that lids must not be able to be opened when under pressure—and when a lid is opened, the contents must not erupt from the pot and cause injury.

That some companies certify their electrically self-powered pressure cookers to comply with UL 136 is evidence that compliance with UL 136 is the standard in the industry. These companies cannot reasonably argue that UL 136 does not apply to their products.

If a product does not comply with published or generally accepted industry standards, this may be evidence of negligence¹⁰—and an unreasonably dangerous product.¹¹ By not complying with industry standards, particularly if claims of safety are made in marketing materials or instruction manuals—including claims of UL certification—the manufacturer is in breach of both express warranties and implied warranties of merchantability.

If a product does not comply with published or generally accepted industry standards, this may be evidence of negligence—and possibly an unreasonably dangerous product.

Causes of Action

In most states, the usual products liability causes of action are available in a pressure cooker case. These include the following:

• Negligent design. The product was not designed to meet the prevailing standards in the industry. Under those standards, pressure cookers must be designed so that the lid cannot be opened with little effort when pressurized. And when the lid is opened, pressure in the pot must be reduced so contents do not erupt, causing injury.
• Negligent manufacturing. While the product was designed to meet the industry standard, one or more components were manufactured or assembled out of specification—which allowed the product to be opened under pressure.
• Strict liability. A pressure cooker that can be opened under pressure does not comply with industry standards, is unreasonably dangerous, and does not meet consumer expectations.
• Breach of implied warranty. A pressure cooker that does not comply with the published or generally accepted standards in the industry for safety is not merchantable.
• Breach of express warranties. Look for a written warranty in the instruction manual related to defects in manufacture.¹² There also may be claims about safety on the pressure cooker’s box or in printed or web marketing materials. If you find language stating that the lid cannot be opened when the product is under pressure, then the lid doing so is a violation of these express warranties.
• Negligent or intentional misrepresentation and fraud. These causes of action are merited when defendants made affirmative statements about the inability of the lid to be opened under pressure. And if the company knew that products were being opened under pressure and consumers were being injured, these claims may support punitive damages.

I do not recommend pleading causes of action based on defective or inadequate warnings. To prevail on such claims, you must prove that the accompanying warnings did not adequately caution a customer not to open the product under pressure. More significantly, you’d have to convince a jury that your client did not know that there was any risk of opening the product under pressure and intentionally opened it under pressure believing there was no danger yet would have read and heeded an adequate warning. This is a hard sell.

Jurisdiction Issues

Many brands of modern pressure cookers have been sold in the United States in the past several years. They are sold in big-box stores, traditional department stores, and online. I’ve found in my cases that many electric pressure cookers on the U.S. market are manufactured in China by several large consumer appliance manufacturers. They are made pursuant to supply agreements for companies that then have their brand name put on the product and arrange for the import, distribution, and sale of their branded product in the U.S. These products are primarily designed by Chinese manufacturers, with slight changes in the appearance, packaging, programs, and touchpads requested by the company that is branding the product as its own.

Often, the actual manufacturer of a pressure cooker is a foreign entity with no jurisdictional nexus to bring it into a case as a party. In these instances, many states have a statute that makes the retailer or distributor an entity liable for a defective product in place of the seller, even if it is otherwise an “innocent seller.”¹³ This usually is the law even in states where the retailer generally is not liable for a product for which it was an innocent seller.¹⁴ And over the past few years, the law has been moving toward holding online marketplaces liable for the defective products that they sell in some jurisdictions.¹⁵ But be aware that this is still in flux and is not the law in all jurisdictions.¹⁶

Discovery

When taking on a pressure cooker case, thorough discovery is key. Here are a few tips to get you started.

Exemplars. Buy these, new and used, from sites like eBay. Try to get the exact model and vintage of the pressure cooker that is the subject of your case. Take the models apart to understand how they work and to uncover potential differences in the lid locking mechanical components in different year models of the same product. (See Figure 3.) You also can use exemplar components from the models in depositions and at trial.

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X-rays. Get industrial X-rays of the subject evidence lid for a nondestructive look at its hidden components. Also X-ray the lids of any exemplar products you may acquire. Most forensic engineering experts will have access to industrial X-ray equipment in their examination lab. (See Figure 2.)

Experts. Hire experts who know the product and have done laboratory testing of exemplars. Contact other plaintiff counsel who have handled similar prior cases for recommendations. Have your expert, wearing protective equipment, use an exemplar to do a videotaped demonstration of the lid opening under pressure and the contents erupting out of the exemplar.

Prior claims. In the first set of requests for production served early in your case, ask for the defendant’s claims database and files on any instances when a consumer reported that the lid of its pressure cooker products opened while under pressure. Also ask for all reports that were the result of the company’s investigation of any of the consumer claims.

Do not accept the defense’s request to limit production to only documents or information for the model at issue in the case. If they refuse or severely limit their responses to just the exact model in your case, take the issue to the court as a discovery dispute—supported by an affidavit from your expert, a Rule 30(b)(6) deposition on the issue of substantial similarity, or both. In my experience, the lid locking technology is usually substantially similar, if not identical, across all models.

Be sure to ask the defendant to include reports on warranty returns, injury claims, and products returned as a term of a settlement. Also ask for products that have been returned to the defendant with claims that the lid of the product opened while the product was under pressure (for nondestructive inspection by you and your experts).

Collaborate. Conduct a federal docket search for any case filed against the manufacturer of the product at issue. Download the docket sheet, complaint, and any relevant documents. Then call the plaintiff attorneys and share information.

I also recommend joining AAJ’s Pressure Cooker Litigation Group.¹⁷ You can connect with other members handling these cases and download sample documents from the Litigation Group library. Then share your own knowledge by uploading your complaint and written discovery requests.¹⁸

Litigating a pressure cooker products liability case requires an expert familiar with these products to support your case, but the facts needed to prove liability are relatively simple and should be apparent from the initial client interview. Your client believed the pressure had been released and began to turn the lid with relatively little effort—and as they did so, the lid blew off, erupting scalding contents.

George E. McLaughlin is the founder of the McLaughlin Law Firm in Denver, Colo., and can be reached at gem@mcllf.com.

Notes

1. Sci. Museum Grp., Papin’s Steam Digester, Sci. & Soc’y Picture Library, https://tinyurl.com/47abs73v.
2. Tim Chin, How Pressure Cookers Actually Work, Serious Eats, Jan. 28, 2022, https://www.seriouseats.com/how-pressure-cookers-work.
3. Roland Ochoa, Pressure Cooker Explosion—Lid Opening Under Pressure, YouTube, Dec. 5, 2018, https://tinyurl.com/mr38dtsk.
4. Junaid Aftab, Pressure Cooker Explosion, YouTube, Mar. 2, 2021, https://tinyurl.com/h2w9xpe3.
5. U.S. Consumer Prod. Safety Comm’n, Crock-Pot 6-Quart Express Crock Multi-Cookers Recalled by Sunbeam Products Due to Burn Hazard, CPSC, Nov. 24, 2020, https://tinyurl.com/2bh646j7.
6. Motion for Class Action Settlement, Chapman v. Tristar Prods., Inc. (N.D. Ohio Jan. 18, 2018) (No. 1:16-cv-01114); Opinion and Order Approving Proposed Settle­ment, Chapman v. Tristar Prods, Inc. (N.D. Ohio Aug. 3, 2018) (No. 1:16-cv-01114).
7. When cooking in a pressure cooker, for every 1 psi above normal atmospheric pressure, the temperature at which water becomes steam is raised by 1 ⅔°C (3°F). For more on how pressure cookers work, see Chin, supra note 2.
8. UL, formerly known as Underwriters Laboratories, is an industry-supported third-party certification company that publishes product safety standards and conducts testing to certify that products meet those standards.
9. Pfeiffer v. Eagle Mfg. Co., 771 F. Supp. 1133 (D. Kan. 1991).
10. Noncompliance with an industry standard may be evidence of negligence. See, e.g., Diaz v. New York Downtown Hosp., 287 A.D.2d 357, 358 (N.Y. App. Div. 2001).
11. Noncompliance with standards may show a defect or unreasonably dangerous condition. See  Wallner v. Kitchens of Sara Lee, Inc., 419 F.2d 1028, 1032–33 (7th Cir. 1969). 
12. For instance, Instant Pot’s warranty reads:
This Limited Warranty is effective for one year from the date of original consumer purchase. Proof of original purchase date and, if requested by an authorized representative of Instant Brands Inc. (“Instant Brands”), the return of your appliance, is required to obtain service under this Limited Warranty. Provided that this appliance is operated and maintained in accordance with written instructions attached to or furnished with the appliance, Instant Brands will, in its sole and exclusive discretion, either: (i) repair defects in materials or workmanship; or (ii) replace the appliance. In the event that your appliance is replaced, the Limited Warranty on the replacement appliance will expire 12 months from the date of original consumer purchase.
 
Instant Pot, Warranty, https://instantpotme.com/warranty/.
 
13. See, e.g., Colorado Product Liability Act, Colo. Rev. Stat. §13-21-402 (retailer may be deemed to be the “manufacturer” of products that it distributed or sold if the manufacture is not subject to jurisdiction).
14. Id.
15. Loomis v. Amazon, 63 Cal. App. 5th 466, 475–83 (Cal. App. Ct. 2021); Bolger v. Amazon, 53 Cal. App. 5th 431, 452–54 (Cal. App. Ct. 2020). See also Michael Waters, Why Amazon’s Product Liability Risk is Growing, Modern Retail, July 22, 2021, https://www.modernretail.co/platforms/amazon-briefing-why-amazons-product-liability-risk-is-growing/; Thomas Murphy III, Is Amazon Liable for Third-Party Sellers’ Products? To Date, The Answer for E-Commerce Retailers May Depend on Where They Are, JD Supra, Aug. 10, 2021, https://www.jdsupra.com/legalnews/is-amazon-liable-for-third-party-9783896/; Eric Chaffin & Steven Cohn, A Stream of Liability, Trial, July 2021, at 20.
16. McMillan v. Amazon, 983 F.3d 194, 201 (5th Cir. 2021); Great N. Ins. Co. v. Amazon, 524 F. Supp. 3d 852, 858 (N.D. Ill. 2021); Oberdorf v. Amazon, 818 F. App’x 138 (3d Cir. 2020).
17. For more information, visit https://www.justice.org/community/litigation-groups/pressure-cookers.
18. AAJ’s Products Liability Section and Products Liability Law Reporter are also great resources. For more information, visit https://www.justice.org/community/sections/products-liability and https://www.justice.org/resources/publications/products-liability-law-reporter.