Research
The building a supplement is made in
The physical plant rules for dietary supplements reach the parking lot, the plumbing, the light bulbs and the trash. Three sections, and one of them is mostly a list of ways a building can contaminate a product.
A rulebook about a place
Product pages talk about ingredients and testing. The supplement manufacturing rules spend an entire subpart on the building.
It is three substantive sections. One on sanitation of the plant and grounds, one on design and construction, and one on records.
The written-procedures requirement here is unusually narrow. It names two things by name: you must establish and follow written procedures "for cleaning the physical plant and for pest control."
Everything else in the subpart is an obligation without a mandated procedure, which is worth noticing when someone points at a written procedure as proof of anything broader.
The rules start outside the door
Grounds have to be kept in a condition that protects against contamination of components, supplements or contact surfaces. Four methods are named and a fifth deals with the neighbors.
Equipment stored properly, litter and waste removed, and weeds or grass cut within the immediate vicinity, so the area does not attract pests, harbor pests, or give them a place for breeding.
Roads, yards and parking lots maintained so they are not a source of contamination where materials or contact surfaces are exposed. Areas drained adequately where seepage or filth could contaminate or breed pests. Waste treatment and disposal systems operated so they are not a source of contamination.
Then the clause about land the firm does not control. Where bordering grounds are not maintained this way, the firm must exercise care by inspection, extermination or other means to exclude pests, dirt and filth.
Water, and the line that decides how it is judged
Water gets two paragraphs, and the split between them is the substantive part.
For all uses where water does not become a component of the supplement, the requirement is water that is safe and sanitary, at suitable temperatures, and under pressure as needed.
Where water is used in a manner such that it may become a component — including when it contacts components, supplements or any contact surface — a different standard applies. It must at a minimum comply with applicable federal, state and local requirements and not contaminate the supplement.
That second category is broader than it first reads. Water touching a contact surface can fall into it, which is why the records section requires proof that this water meets the requirement.
Plumbing is a contamination rule in disguise
The plumbing paragraph lists five duties, and only the first is about supply.
Carry sufficient water to required locations. Properly convey sewage and liquid disposable waste out of the plant.
Avoid being a source of contamination to components, supplements, water supplies or any contact surface, or creating an unsanitary condition.
Provide adequate floor drainage wherever floors are subject to flooding-type cleaning or where operations discharge liquid onto the floor.
And the one that names the failure mode directly. There must be no backflow from, or cross connection between, piping that discharges waste water or sewage and piping that carries clean water. The clean side covers water used for manufacturing, cleaning contact surfaces, bathrooms and hand-washing.
Pests, toxics, and a specific exception for dogs
Animals and pests are not allowed in any area of the plant. The regulation then carves out one case: guard or guide dogs are allowed in some areas if their presence will not result in contamination.
Effective measures must exclude pests and protect materials and contact surfaces from them. Insecticides, fumigants, fungicides and rodenticides may not be used unless precautions are taken to protect against contamination.
Toxic materials are restricted to four permitted purposes: maintaining clean and sanitary conditions, laboratory testing procedures, maintaining or operating the plant or equipment, and use in the plant's operations.
Cleaning compounds and sanitizing agents must be free from microorganisms of public health significance and safe and adequate under the conditions of use. All of these materials must be identified and held so they do not contaminate anything.
Separation is the design principle
The design and construction section is built around preventing mix-ups and cross-contamination, and it is specific about where.
The plant must have, and the firm must use, separate or defined areas of adequate size or other control systems for seven named operations. The regulation gives computerized inventory controls and automated systems of separation as examples of those control systems.
Receiving, identifying, holding and withholding from use components, supplements, packaging and labels. Separating materials awaiting a material review decision, reprocessing, or disposal after rejection.
Separating the manufacture, packaging, labeling and holding of different product types, including different supplements and other foods, cosmetics and pharmaceutical products. Laboratory analyses and supplies. Cleaning and sanitizing contact surfaces. Packaging and label operations. Holding components or supplements.
That third item is the one that matters most for a facility running several product lines. Different product types are supposed to be separated from each other, not merely from dirt.
Floors, ducts, air and light bulbs
Construction requirements are listed as physical features. Floors, walls and ceilings that can be adequately cleaned and kept clean and in good repair.
Fixtures, ducts and pipes that do not contaminate by dripping, other leakage or condensate. Adequate ventilation or environmental control equipment that minimizes odors and vapors where they could contaminate.
Temperature and humidity control equipment where it is necessary to ensure the quality of the supplement. Aisles and working spaces wide enough and unobstructed enough that people can work without contaminating anything with their clothing.
Fans and air-blowing equipment must be located and operated so they minimize the potential for microorganisms and particulate matter to contaminate.
And a small, telling one. Safety-type light bulbs, fixtures, skylights or other glass or glass-like materials are required where those are suspended over exposed components or supplements. The exception is a plant otherwise built to protect against breakage.
What the records prove, and what they do not
The records section for this subpart names three things.
Records kept in accordance with the part's general records subpart. Records of the written procedures for cleaning the plant and for pest control.
And records showing that water, where used in a manner such that it may become a component of the supplement, meets the standard in the water paragraph.
That is a narrow list for a broad subpart. Most of what this subpart requires — the drainage, the separation, the aisles, the bulbs — leaves no mandated record here. It shows up in an inspection, not a file a buyer could ask for.
What to take from it
These requirements bind whoever manufactures, packages, labels or holds a dietary supplement. That is frequently not the company whose brand is on the label.
The most useful idea for a reader is the separation principle. A facility handling several product types is supposed to have defined areas or control systems keeping them apart, and cross-contamination between product lines is the risk that principle exists to address.
The second is the water distinction. Water that may become a component is held to a different standard, and it is the one requirement in this subpart with a records obligation attached.
None of this is published, and nothing here describes any particular facility. It describes what the rule asks of one.
Key takeaways
- The physical plant subpart requires written procedures for exactly two things: cleaning and pest control.
- Grounds requirements reach parking lots, drainage, waste systems and neighboring land the firm does not control.
- Water that may become a component of the product is held to a separate standard, with a records obligation.
- Plumbing rules name backflow and cross connection between waste and clean water lines as the failure to prevent.
- Seven operations must be separated by defined areas or other control systems, including different product types.
- Most of the subpart leaves no mandated record; it surfaces in an inspection rather than in a file.
Frequently asked questions
What written procedures does the physical plant subpart require?
Two, named explicitly: procedures for cleaning the physical plant and for pest control. The rest of the subpart imposes obligations without mandating a written procedure for each, which is why a firm having those two procedures does not by itself speak to the rest.
Do the rules cover water used in a supplement?
Yes, and they split it. Water that does not become a component must be safe and sanitary, at suitable temperatures, and under pressure as needed. Water used in a manner such that it may become a component must at a minimum comply with applicable federal, state and local requirements, and must not contaminate the supplement. That category includes water contacting components or contact surfaces. Records must show it meets that standard.
Does a supplement facility have to separate different products?
Yes. The design requirements call for separate or defined areas of adequate size, or other control systems such as computerized inventory controls or automated separation, for seven named operations. One of them is separating the manufacture, packaging, labeling and holding of different product types, including different supplements and other foods, cosmetics and pharmaceutical products.
Are animals allowed in a supplement plant?
Not generally. The regulation states you must not allow animals or pests in any area of the physical plant. There is one carve-out. Guard or guide dogs are allowed in some areas if their presence will not result in contamination of components, supplements or contact surfaces.
Can I verify any of this about a product I bought?
No. Almost nothing in this subpart generates a record a buyer can request, and the only records it names are the cleaning and pest control procedures and the water documentation. These are inspection materials. The obligations also fall on whoever physically makes or holds the product, which is often a contract facility rather than the brand.
Sources
Each document below is named as it names itself, with the date printed on that document rather than the day it was read.
- 21 CFR 111.15, What sanitation requirements apply to your physical plant and grounds? — Electronic Code of Federal Regulations, title 21, August 2026
- 21 CFR 111.16, What are the requirements under this subpart C for written procedures? — Electronic Code of Federal Regulations, title 21, August 2026
- 21 CFR 111.20, What design and construction requirements apply to your physical plant? — Electronic Code of Federal Regulations, title 21, August 2026
- 21 CFR 111.23, Under this subpart C, what records must you make and keep? — Electronic Code of Federal Regulations, title 21, August 2026