When you see "NSF certified" stamped on commercial kitchen equipment or listed in an air fryer's spec sheet, that mark most likely traces back to NSF/ANSI 51 - the foundational U.S. standard for food equipment materials. It's one of those certifications that sounds narrow but actually covers a wide swath of what ends up in your kitchen and near your food.
NSF International (formerly the National Sanitation Foundation) published the first version of Standard 51 in the 1970s. The standard has been updated regularly - most recently in 2023 - and is now jointly maintained by NSF and ANSI (American National Standards Institute). The formal title is NSF/ANSI 51: Food Equipment Materials, and its core job is to verify that the materials used to make food equipment won't contaminate food.
What NSF/ANSI 51 Actually Tests
The standard covers a deceptively broad scope. Any material that contacts food in commercial equipment - coatings, plastics, rubber seals, gaskets, solder, adhesives, metals, glass-like materials, and lubricants - must meet NSF/ANSI 51 requirements before it can be used in certified equipment. Here's what the testing evaluates:
Material formulation review. Every non-metal material (plastics, elastomers, coatings) must be made from substances permitted as indirect food additives under U.S. 21 CFR (Code of Federal Regulations), specifically the food contact sections CFR 174 through 179. NSF's technical team reviews the full formulation against those FDA-approved ingredient lists.
Extractables and migration testing. The standard evaluates whether a material will transfer harmful substances into food under realistic use conditions. This involves exposing the material to food simulants - standardized solutions that mimic acidic, aqueous, or fatty foods - at elevated temperatures for defined contact times. If chemical migrants exceed established thresholds, the material fails.
Heavy metals testing. NSF tests for lead, cadmium, and other regulated heavy metals. The 2023 update significantly expanded lead requirements: all materials in contact with water, coffee, or tea intended for human consumption must now be evaluated for weighted average lead content under NSF/ANSI/CAN 372 - not just products with brass or bronze components. Intentionally added lead is prohibited on all food contact surfaces, and unintentional lead impurities must remain below 0.06%.
Taste and odor evaluation. Materials are assessed to confirm they don't impart detectable off-flavors or odors to food. This protects both safety and food quality.
Coating adhesion and physical durability. Coatings must pass cleanability, corrosion resistance, impact resistance, abrasion resistance, and heat resistance tests. A coating that flakes, chips, or degrades under normal use conditions can both contaminate food physically and expose base materials that weren't intended to contact food.
Ongoing surveillance. Certification isn't a one-time event. NSF conducts annual facility audits and periodic product retesting. If a manufacturer changes a material formulation, the product must be re-evaluated. This is what separates certification from self-declaration.
An Important Nuance: Fluoropolymer Coatings
Here's where families researching air fryers and nonstick cookware need to pay close attention: NSF/ANSI 51 contains an exemption for fluoropolymer coatings applied to heated food zones.
Fluoropolymers - which include PTFE (Teflon) and related PFAS compounds - are exempt from the standard's usual extractables testing requirements. The rationale has historically been that cured PTFE polymer is chemically inert and won't migrate into food under normal use conditions. So a nonstick air fryer basket coated with PTFE can carry NSF 51 certification for its construction and lead content without having been tested for PFAS migration specifically.
This is the key gap that NSF 537 - the new PFAS-free certification launched in March 2025 - was designed to close.
NSF 537: The PFAS-Free Layer on Top of NSF 51
On March 24, 2025, NSF International launched Certification Guideline 537: PFAS-Free Products for Nonfood Compounds and Food Equipment Materials. It's the first third-party PFAS-free certification specifically designed for food equipment.
To qualify for NSF 537, a food equipment material must:
1. First hold NSF/ANSI 51 certification (the baseline material safety requirement), AND
2. Contain no intentionally added PFAS of any kind, AND
3. Test below 50 parts per million total organic fluorine (TOF) - the analytical threshold for confirming no PFAS contamination at any meaningful level, AND
4. Use no post-consumer recycled materials that could introduce PFAS traces
TOF testing must be repeated annually to maintain the certification. This matters because PFAS can enter a material through cross-contamination during manufacturing even if they aren't intentionally added.
The first company to receive NSF 537 certification was ROCOL, for food-grade lubricants. For families evaluating air fryers and cookware, NSF 537 is now the most meaningful third-party signal that a food-contact coating is genuinely PFAS-free - not just PFOA-free or marketing-claim free. Certified products are listed in NSF's public database at listings.nsf.org.
How NSF 51 Differs from NSF 42, 53, and 58
There's genuine confusion in the parenting community between NSF's food equipment standard and its water filter standards. They're distinct programs that test for entirely different things.
NSF/ANSI 51 - Food Equipment Materials: Applies to commercial and home food equipment. Tests the materials used to build equipment (coatings, metals, plastics, gaskets) for food safety. You'll see this on air fryers, commercial mixers, cutting boards, steam tables, and food prep surfaces. It does not test water filtration performance.
NSF/ANSI 42 - Aesthetic Effects: A water filter standard. Certifies that a filter reduces chlorine taste and odor, improving how water tastes and smells. It does not address health contaminants like lead or PFAS.
NSF/ANSI 53 - Health Effects: A water filter standard certifying reduction of specific health-risk contaminants including lead, cysts, and volatile organic compounds. Some NSF 53 certifications also cover PFAS reduction for long-chain compounds. Completely different scope from NSF 51.
NSF/ANSI 58 - Reverse Osmosis Systems: The most comprehensive water filter standard. Certifies that an RO system reduces a broad spectrum of dissolved contaminants - arsenic, nitrates, fluoride, PFAS - to safe levels. NSF 58 certified systems with PFAS claims achieve 95-99% removal. Not related to food equipment materials.
When you're shopping for a water filter, look for NSF 53 or NSF 58. When you're evaluating cookware or an air fryer's coatings, NSF 51 (and ideally NSF 537) is what matters.
How Manufacturers Get NSF 51 Certified
The certification process is rigorous, typically taking 4 to 18 months depending on product complexity. Here's how it works:
- 1.Application and documentation. The manufacturer submits full material formulations, product specifications, and manufacturing process documentation to NSF.
- 2.Formulation review. NSF's technical team cross-references every ingredient in non-metal components against 21 CFR food contact regulations. Any ingredient not approved as an indirect food additive triggers a reformulation request.
- 3.Testing protocol development. Based on the product's intended use, NSF determines which physical and chemical tests apply - extractables panels, heavy metals analysis, taste/odor evaluation, coating durability tests.
- 4.Laboratory testing. NSF-accredited labs test product samples under the conditions of the assigned protocol.
- 5.Facility audit. An NSF auditor conducts an on-site inspection of the manufacturing facility to verify production processes, quality control systems, and material traceability.
- 6.Certification decision. If testing and audit pass, NSF issues certification. The product is added to the public NSF certified food equipment database.
- 7.Annual surveillance. NSF retests products and audits facilities on a recurring schedule. Material changes require re-evaluation and re-certification.
Manufacturers pay ongoing annual fees to maintain certification. This cost is part of why NSF certification is more common among commercial equipment brands and premium consumer cookware lines than budget products.
Why This Matters for Air Fryer and Cookware Safety
For families making purchasing decisions around air fryers and cookware, NSF/ANSI 51 is a useful baseline - but not the whole story.
NSF 51 tells you that a product's construction materials have been independently reviewed for compliance with FDA food contact regulations, that lead content has been verified, and that the manufacturer is subject to ongoing audits. It's a real credential, not marketing language.
What NSF 51 does not tell you - because of the fluoropolymer exemption - is whether a nonstick coating contains PTFE or other PFAS. An air fryer basket with a PTFE coating can display NSF 51 certification without that coating having been tested for PFAS migration. This is why the PFAS-free claim on cookware requires additional scrutiny beyond NSF 51 alone.
The emerging standard of care for families who want to minimize PFAS exposure from food contact surfaces is to look for:
- NSF/ANSI 51 certification as the baseline (material safety, lead, extractables), PLUS
- NSF 537 PFAS-free certification as the additive layer (confirms no PFAS in the material at 50 ppm TOF threshold), OR
- An explicit PTFE-free and PFAS-free claim backed by third-party testing data, OR
- Uncoated materials - stainless steel, cast iron, ceramic - that are PFAS-free by chemistry and don't require coating certifications
For families in California, the context expands further. California AB 1200, which took full effect for product labeling in January 2024, requires cookware manufacturers to disclose on product labels and websites all intentionally added chemicals from a designated list - including PFAS - present in any food-contact surface. AB 1200 also prohibits brands from claiming a product is "PFAS-free" if it contains any PFAS compound, including PTFE. This means California-sold products now carry mandatory chemical disclosure that, in theory, gives consumers more information than NSF 51 alone provides.
How to Verify NSF Certification
NSF maintains a public, searchable certification database at listings.nsf.org. You can search by company name, product type, or certification standard. For food equipment, filter by NSF/ANSI 51 to see certified materials and products.
For NSF 537 PFAS-free certifications specifically, certified nonfood compounds appear in the NSF White Book and certified food equipment materials appear in the NSF Certified Food Equipment listing - both accessible through the same listings.nsf.org portal.
A few important caveats when using the database: certification is tied to specific product models and formulations, not brand names broadly. A manufacturer may have one NSF 51-certified coating and ten other products that aren't certified. Always search the specific product, not just the brand.
Also: the NSF mark on a product should match exactly what's listed in the database. "Tested to NSF standards" is not the same as NSF certified - a distinction NSF itself emphasizes. If a product claims certification but the listing can't be found in the database, that's a red flag worth pursuing with the manufacturer directly.
The Bottom Line for Families
NSF/ANSI 51 is the right starting point when evaluating food equipment materials - it means the materials have been independently tested against FDA food contact regulations, not just self-declared safe by the manufacturer. The 2023 update strengthened lead requirements meaningfully.
But NSF 51 alone doesn't answer the PFAS question for coated cookware and air fryer baskets. That's where NSF 537 (launched March 2025) steps in as the most credible additive certification. Until NSF 537 adoption becomes widespread, families who want to minimize PFAS from cooking surfaces are best served by choosing uncoated stainless steel or verified-PFAS-free ceramic alternatives - or verifying directly with manufacturers whether their coatings have been tested under NSF 537.