NSF/ANSI 51: What Food Equipment Materials Certification Covers
NSF/ANSI 51 is the American National Standard for the materials commercial food equipment is built from: work surfaces, gaskets, tubing, valves, and the sealants that join and seal all of it. Here is what the certification evaluates, how contact zones change what a listing allows, and the three claims buyers most often mistake for it.
Last updated: August 26, 2026
The short version
- NSF/ANSI 51, Food Equipment Materials, sets minimum public health and sanitation requirements for materials used to build commercial food equipment. It is a materials standard, not an equipment design standard and not a company credential.
- Certification is granted by contact zone. A food zone listing also covers splash and nonfood zones. A splash zone listing does not cover food zones.
- The standard says nothing about mold, mildew, or antimicrobial performance. Those claims come from separate test methods, when they are supported at all.
- FDA approved, USDA approved, and NSF registered are three different things, and none of them is NSF/ANSI 51 certification.
- Certification attaches to a named product with stated conditions. Check the listing for zone, type of food, and maximum use temperature before you write it into a spec.
What NSF/ANSI 51 covers
The standard is titled Food Equipment Materials. NSF International writes it through its Joint Committee on Food Equipment, using the consensus process described by the American National Standards Institute, which is what makes it an American National Standard rather than a house rule. NSF adopted it in 1978 and has revised it repeatedly since. The current edition is NSF/ANSI 51-2025.
Its purpose clause is narrow and worth reading literally. The standard sets minimum public health and sanitation requirements for materials used in the construction of commercial food equipment, so that the composition and surface finish of a material will not adulterate food or render equipment difficult to clean and sanitize. Everything else it does follows from those two ideas.
Scope runs to the materials and finishes used to manufacture food equipment, and to components including tubing, sealants, gaskets, and valves. NSF/ANSI 51 also acts as the reference document for the rest of the NSF food equipment standards, so a unit certified to one of the equipment standards already carries these material requirements underneath it.
| Requirement area | What it asks of a material |
|---|---|
| Material formulation | Food zone materials must be built from substances recognized or sanctioned as safe for the intended use under federal food additive rules |
| Smooth and easily cleanable | Surface finish that can be cleaned and sanitized in service |
| Corrosion resistance | Holds up to the food, cleaners, and sanitizers it will see |
| Abrasion, impact, and heat resistance | Applied as relevant to the material and its end use |
| Coating adhesion | For metallic and organic coatings, that the coating stays put |
What the standard leaves out matters as much. Its foreword states that it does not define extraction test methods or acceptance criteria for chemical migration from food contact surfaces, and cites federal regulations instead. It also excludes mechanical and electrical safety, which other bodies cover. And it certifies materials, not equipment design and not manufacturers.
Food, splash, and nonfood zones
Every NSF/ANSI 51 listing is granted for a zone, and the zone is the part of the listing that decides whether a material can touch food. The zones describe how likely food contact is on a given surface.
| Zone | What it covers | What a listing in this zone allows |
|---|---|---|
| Food zone | Surfaces intended for direct food contact, plus surfaces that consumable food or condensation may contact and then drain, drip, or splash back onto food or onto a food contact surface. | Also acceptable in splash and nonfood zones. |
| Splash zone | Surfaces exposed to routine soiling from splashes and spills during operation that are not intended for contact with consumable food. | Also acceptable in nonfood zones. Not certified for food zones. |
| Nonfood zone | Surfaces not exposed to food or splashes, though they may collect minor dirt and debris. | Nonfood zone only. |
The rule runs one way, and NSF prints it as a footnote on the listings themselves: food zone items are also acceptable in splash and nonfood zones, and splash zone items are also acceptable in nonfood zones. It does not work in reverse.
Zone also changes what the material had to pass. Everything certified to the standard is evaluated for smoothness, cleanability, and corrosion resistance as applicable to the material and its end use. Only materials certified for food zones meet the toxicological safety requirements. NSF describes that food zone evaluation as a formulary review against FDA requirements. Be precise about that wording, because the sister standard works differently: extraction testing is the evaluation method for NSF/ANSI 61 drinking water components, not for NSF/ANSI 51.
The trap: a listing that reads "for Splash Zone" is not a food contact credential. Buyers see the NSF mark, stop reading, and put a splash zone material on a food contact joint. The zone is printed on the listing. Read it before you specify.
Gaskets, sealants, rubber, and other components
People arrive at this standard looking for something specific: a certified gasket, a certified rubber part, a certified sealant. All three sit inside its scope, which names tubing, sealants, gaskets, and valves as components the standard applies to. NSF groups certified products in the listings by material and zone, so a search returns entries like silicone for food zone or coatings for splash zone rather than a single generic pass.
For rubber and elastomeric components the underlying federal reference is 21 CFR 177.2600, titled Rubber articles intended for repeated use, which sits in the FDA indirect food additive rules for polymers. It lists the polymers and adjuvant substances a repeated-use rubber article may be built from, and it caps what the finished food contact surface may give up. In refluxing distilled water, total extractives may not exceed 20 milligrams per square inch over the first 7 hours or 1 milligram per square inch over the next 2. For fatty food the n-hexane limits are 175 and 4 milligrams per square inch over the same two periods.
Match the citation to what the material actually is. Adhesives fall under 21 CFR 175.105 and resinous and polymeric coatings under 21 CFR 175.300. Citing the wrong part is the most common error on a food area spec sheet, and it is easy to catch: a cured sealant bead is not automatically a rubber article.
Certification attaches to a product, not a brand. A certified and an uncertified product from the same manufacturer can share a family name, a color, and a cartridge that looks identical on the shelf. Match the exact trade designation to the listing, every time.
What NSF/ANSI 51 says about mold: nothing
A certified silicone in a walk-in cooler can still grow mildew on its surface if the room stays wet. NSF/ANSI 51 has nothing to say about that, and this is the single most common misreading of the standard. Nothing in its published scope or requirement list addresses mold, mildew, or fungal growth. The requirements are material formulation, cleanability, corrosion resistance, abrasion resistance, impact resistance, heat resistance, and coating adhesion. Growth resistance is not among them.
The rest of the NSF standards family shows where that boundary sits. NSF/ANSI 52, for supplemental flooring, does include resistance to microbiological growth in its requirements. And NSF prints a footnote on coating entries in the food equipment listings stating the product was not tested by NSF for efficacy at limiting the spread of bacteria. Where a growth or hygiene claim is in scope, NSF names it.
Mold resistance is measured somewhere else entirely. ASTM D3273 runs interior coating films in an environmental chamber for four weeks and rates surface growth on a 0 to 10 scale. ASTM G21 determines the resistance of synthetic polymeric materials to fungi. A product can hold an NSF/ANSI 51 listing and a D3273 rating at the same time. Each answers a separate question, and neither one implies the other.
Reading a datasheet: when an NSF/ANSI 51 line sits next to a mold or mildew resistance claim, those are two claims with two different sources. Ask for the test method and the rating behind the mold claim. The NSF listing does not support it, and the two lines being adjacent does not make them one credential.
FDA approved, USDA approved, and NSF registered
Three phrases circulate constantly on food area product literature. None of them is NSF/ANSI 51 certification, and one describes a government program that has not existed since 1998.
| The claim | What it actually is | Who stands behind it |
|---|---|---|
| FDA approved | FDA approves no sealant, gasket, or other finished food contact article. It authorizes substances and their conditions of use through regulations such as 21 CFR 177.2600. | The manufacturer. FDA puts the burden of compliance on the maker of the material and points buyers to a letter of guaranty. |
| USDA approved | Obsolete. FSIS eliminated prior approval of nonfood compounds and proprietary substances effective with its February 13, 1998 policy notice at 63 FR 7319. | Nobody. USDA has issued no such approvals since 1998. |
| NSF registered | The NSF Nonfood Compounds Registration Program, the private continuation of the old USDA listing program. Formulation, label, and traceability review, listed in the NSF White Book with a registration number and category code. | NSF, as a registration rather than certification to a standard. NSF states the listing is not an endorsement of performance or efficacy claims. |
| NSF/ANSI 51 certified | Third party certification of the material to an American National Standard, granted for a stated contact zone and published in the NSF food equipment listings. | NSF, backed by formulation review, testing, manufacturing plant audits, and annual reverification. |
On the FDA side the mechanism is worth understanding, because it is not a loophole. FDA authorizes substances and their conditions of use, and a manufacturer determines that its finished article conforms. FDA states that ensuring compliance is the responsibility of the manufacturer of the food contact substance, and it points buyers who want documentation toward a letter of guaranty from the supplier. A conformance claim to 21 CFR 177.2600 is real and useful. It is just self-declared, with no agency record behind it, which is exactly the gap third party certification fills.
On the USDA side, FSIS published its policy change on February 13, 1998 at 63 FR 7319, eliminating prior approval for proprietary substances and nonfood compounds and putting the responsibility on establishments to determine that what they use is safe and effective. NSF picked up the listing function as a private program. Sealants do appear in that program under their own registration codes. A registration in any of them is a compound review, not a material certification to NSF/ANSI 51, and the two live in separate databases.
In an FSIS-inspected plant, go one step further. FSIS guidance on third party authorities states that the agency will not treat any particular third party certification as definitive evidence of compliance, and that a letter of assurance from the supplier is the appropriate documentation for chemical compounds used in food processing, handling, and storage areas. Keep the certification listing and get the letter.
Where certification gets required
The standard is voluntary on its own. It becomes binding when another document references it, and in a food facility several do.
Start with the FDA Food Code, keeping in mind that it is a model rather than federal law. FDA publishes it for state, local, and tribal regulators to adopt, and adoption varies by jurisdiction and by edition. Section 4-101.11 sets what multiuse food contact materials must be: safe, durable, corrosion resistant, nonabsorbent, heavy enough to survive repeated warewashing, finished to a smooth and easily cleanable surface, and resistant to pitting, chipping, crazing, scratching, scoring, distortion, and decomposition. Section 4-101.19 carries the splash analogue, requiring nonfood contact surfaces exposed to splash, spillage, or other food soiling to be corrosion resistant, nonabsorbent, and smooth.
Certification enters at Section 4-205.10, which says food equipment certified or classified for sanitation in conformance to a recognized American National Standard by an ANSI-accredited certification program is deemed to comply with Parts 4-1 and 4-2 of that chapter. The FDA list of recognized American National Standards for food equipment includes NSF/ANSI 51.
Write the spec to the standard, not the certifier. Section 4-205.10 accepts any ANSI-accredited certification program certifying to a recognized American National Standard. A line that reads "must be NSF certified" is narrower than the Food Code and can exclude an equally valid listing. "Certified to NSF/ANSI 51 for food zone use by an ANSI-accredited certification program" says what you actually need.
Beyond the code, the requirement usually arrives through one of these:
- Health department plan review and inspection. Certification is often the evidence asked for that a sealed joint or a surfacing material meets the construction requirements.
- Third party food safety audits. Audit schemes used by food manufacturers and their customers ask for material documentation on food area construction and repairs.
- Buyer and engineering specifications. Equipment schedules and facility specs commonly require certified materials in food and splash zones as a blanket rule.
- Facility types. Food and beverage processing plants, commercial kitchens, bottling and packaging lines, and cold storage, including walk-in coolers and freezers in food service.
Terminology note. The Food Code term food-contact surface and the NSF term food zone overlap but are defined separately in separate documents. They are close enough to reason with and not close enough to use as synonyms in a spec table. Say which document you are citing.
How to verify a listing
- Search the NSF food equipment certification listings at info.nsf.org/Certified/Food and filter to NSF/ANSI 51. NSF states these listings are updated each business day and are the current online listing for NSF certified products.
- Match the trade designation on the container, the gasket, or the part to the entry exactly. Certification attaches to a named product.
- Read the zone in the product group heading, which reads like silicone for food zone or coating for splash zone. That is the food contact answer.
- Check the conditions printed with the entry: type of food, and maximum temperature of use in degrees Fahrenheit. A food zone silicone listed to a given temperature is not a blanket approval for every duty in the plant.
- Check the facility. Listings show the manufacturing location separately from the company address, which matters when a product line is made in more than one plant.
- Save a copy with your facility documentation so it is on hand at inspection or audit time rather than something you go looking for while an inspector waits.
Not a listing: "meets NSF requirements," "NSF compliant," and a bare NSF logo with no standard number beside it. If the product is not in the database, it is not certified, whatever the literature implies. A registration number from the White Book is not a certification listing either.
Specifying an NSF/ANSI 51 sealant
A food area joint has to satisfy two separate requirements at once, and they come from two different standards. NSF/ANSI 51 answers whether the cured material belongs in that zone. ASTM C920 answers whether the sealant will hold the joint, through its type, grade, class, and use classification. A plant joint spec often reads as both: an ASTM C920 silicone that also carries an NSF/ANSI 51 food zone listing.
Many listed sealants are 100 percent silicone, because it cures to a nonabsorbent surface that cleans well and tolerates a wide temperature range. Cold rooms are often not the limiting case. Cook lines, hot equipment, and wash-down are, so check the listed maximum use temperature against the actual duty rather than assuming silicone covers it. The high-temperature sealant guide works through where that limit actually binds.
For cold storage, the walk-in cooler and freezer sealant guide covers where to seal, application temperature limits, and cure behavior in a room that stays cold. For zone requirements mapped across a whole plant, the food processing sealants guide goes area by area.
The NSF/ANSI 51 certification on the sealants below is stated on each manufacturer's technical data sheet. Before you write one into a specification, confirm the current listing, its zone, and its temperature conditions in the NSF database using the steps above.
Sealants Related to NSF/ANSI 51, Stocked by the Case
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Tell us the zone, the temperature range, and how much you need, and we will quote case and pallet pricing on US-made silicones that list NSF/ANSI 51 on the manufacturer datasheet. Typical turnaround: one business day.
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Frequently Asked Questions
What does NSF/ANSI 51 certified mean?
NSF/ANSI 51 is the American National Standard titled Food Equipment Materials. A certified product has been evaluated by NSF against that standard for a stated contact zone and appears in NSF’s public certification listings. The evaluation covers material formulation for food zone use, a smooth and easily cleanable surface, corrosion resistance, and, depending on the material, abrasion, impact, and heat resistance plus coating adhesion. NSF backs certification with manufacturing plant audits and annual reverification, which is what separates it from a claim printed on a datasheet.
Does NSF/ANSI 51 mean a material resists mold or mildew?
No. Nothing in the standard’s published scope or requirement list addresses mold, mildew, or fungal growth. Its requirements are material formulation, cleanability, corrosion resistance, abrasion resistance, impact resistance, heat resistance, and coating adhesion. NSF is explicit about growth resistance where a standard does cover it: NSF/ANSI 52 for supplemental flooring includes resistance to microbiological growth, and NSF prints a footnote on coating listings stating the product was not tested for efficacy at limiting the spread of bacteria. Mold resistance is measured by separate methods such as ASTM D3273 and ASTM G21.
Are gaskets covered by NSF/ANSI 51?
Yes. The scope of the standard names components including tubing, sealants, gaskets, and valves alongside the materials and finishes used to manufacture food equipment. A certified gasket appears in NSF’s listings under its trade designation with the zone it is certified for, the type of food it covers, and a maximum use temperature. Check the zone before you specify it: a gasket listed for splash zone use is not certified for food contact.
Is there such a thing as an FDA approved sealant or gasket?
No. FDA does not approve finished food contact articles. It authorizes substances and their conditions of use through regulations such as 21 CFR 177.2600, which covers rubber articles intended for repeated use. FDA states that it is the responsibility of the manufacturer to ensure a food contact material complies with the applicable authorizations, and it suggests asking the manufacturer for a letter of guaranty. So FDA compliant on a datasheet is a self-declared conformance claim, not an approval, and no FDA registration number sits behind it.
Is USDA approved still a real credential for food area materials?
No. FSIS eliminated its prior approval program for nonfood compounds and proprietary substances in a policy notice published February 13, 1998 at 63 FR 7319, and establishments became responsible for determining that what they use is safe and effective. The private successor is the NSF Nonfood Compounds Registration Program, which continues the old listing function. Anything sold today as USDA approved is describing a program that ended in 1998.
Does NSF registered mean the same thing as NSF/ANSI 51 certified?
No, and the difference matters. Registration is the NSF Nonfood Compounds Registration Program, a review of a chemical compound’s formulation, label, and traceability that lists the product in the NSF White Book with a registration number and a category code. Certification to NSF/ANSI 51 is third party certification of a material to an American National Standard, granted by contact zone and published in the NSF food equipment listings. They are separate programs with separate databases and separate marks. Sealants do appear in that scheme under their own registration codes, but a registration there is a compound review rather than a material certification to NSF/ANSI 51.
What is the difference between a food zone listing and a splash zone listing?
A food zone covers surfaces intended for direct food contact plus surfaces that food or condensation may touch and then drain, drip, or splash back onto food or onto a food contact surface. A splash zone covers surfaces soiled by splashes and spills during normal operation that are not intended for contact with food. The rule runs one way: a material certified for a food zone is also acceptable in splash and nonfood zones, while a material certified for a splash zone is not certified for food zones. Only food zone materials are evaluated against the toxicological safety requirements of the standard.
What is the difference between NSF/ANSI 51 and NSF/ANSI 61?
NSF/ANSI 51 covers materials used to build commercial food equipment, and NSF evaluates them by reviewing the formulation against FDA requirements. NSF/ANSI 61 covers products, components, and materials in contact with drinking water, and it is evaluated by extraction testing against health effects requirements. A product certified to one is not certified to the other. Food equipment and food areas point to 51, potable water systems point to 61.
Is NSF/ANSI 51 required by law?
The standard itself is voluntary. It becomes binding when a document references it. The FDA Food Code, which is a model that state, local, and tribal regulators adopt rather than federal law, says in Section 4-205.10 that food equipment certified or classified for sanitation in conformance to a recognized American National Standard by an ANSI-accredited certification program is deemed to comply with its equipment provisions, and the FDA list of recognized standards for food equipment includes NSF/ANSI 51. Buyer specifications, health department plan reviews, and third party food safety audits reference it as well. Note that 4-205.10 accepts any ANSI-accredited certification program, so a specification that demands NSF by name is narrower than the Food Code.
How do I verify that a product is NSF/ANSI 51 certified?
Search the NSF food equipment listings at info.nsf.org/Certified/Food and filter to NSF/ANSI 51. NSF states that those listings are updated each business day and are the current online listing for NSF certified products. Match the trade designation on the container or the part to the entry exactly, read the zone in the product group heading, and check the conditions printed with the entry: type of food and maximum temperature of use. Keep a copy with your facility documentation so it is on hand at inspection or audit time.
Which edition of NSF/ANSI 51 is current?
NSF/ANSI 51-2025. NSF adopted the standard in 1978 and has revised it repeatedly since. Two recent changes are worth knowing. The 2023 edition extended weighted average lead content evaluation under NSF/ANSI/CAN 372 to equipment having any materials in contact with water, coffee, or tea intended for human consumption, where previously that applied only to equipment with brass or bronze materials. The 2025 edition revised the language on glass and glass-like materials. Superseded editions stay available for purchase, which is why they get cited as current by mistake.
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