A Primer for 3-A Sanitary Standards and 3-A Accepted Practices

This overview is intended as a very basic introduction to 3-A Sanitary Standards and 3-A Accepted Practices. This information is intended for anyone with a specific interest in 3-A Sanitary Standards (e.g. equipment manufacturers, equipment purchasers, engineering managers, quality assurance professionals), as well as those with a more general interest in hygienic equipment design. It provides some essential background information on 3-A Sanitary Standards, Inc. (3-A SSI) and the 3-A Symbol, then a description of the key criteria common to 3-A Sanitary Standards and 3-A Accepted Practices. More in-depth information on many subjects in this ‘primer’ can be found in other sections of the 3-A SSI web site.

What is ‘3-A’ and what’s special about a ‘3-A Standard’?

Many people wonder, what exactly is a ‘3-A Standard’ and what makes these standards distinct among all other types of equipment or materials standards? The first standards known commonly as ‘3-A Standards’ were introduced in the 1920s for milk pipe fittings. The designation of ‘3-A’ is derived from the cooperation of the three interest groups that cooperated to develop these standards – professional sanitarians, equipment fabricators, and processors. These groups included the forerunners of today’s associations that represent these interest groups, including the International Association for Food Protection, the Food Processing Suppliers Association, and the International Dairy Foods Association and the American Dairy Products Institute. Today, these associations, along with the 3-A Administrative Symbol Council, a representative of the USDA and the FDA, are founding members of the current organization, 3-A Sanitary Standards, Inc. (3-A SSI).

Unlike other types of equipment standards that pertain to mechanical properties, electrical or personnel safety, today’s 3-A Sanitary Standards specify the criteria for the design and fabrication of equipment that comes into contact with food. The guiding purpose of 3-A Sanitary Standards is to protect public health by using sanitary equipment. Specifically, the goal of 3-A Sanitary Standards is to:

  • Protect food from contamination,
  • Ensure that all product contact surfaces can be mechanically cleaned, and be dismantled easily for manual cleaning or inspection.

3-A SSI currently maintains 70 different 3-A Sanitary Standards in the following general categories of equipment:

  • Vessels
  • Fillers
  • Valves & Fittings
  • Pumps & Mixers
  • Heat Exchangers
  • Conveyors & Feeders
  • Instruments
  • Concentrating Equipment
  • Farm/Raw Milk
  • Cheese & Butter Equipment

3-A SSI also maintains a series of 3-A Accepted Practices for the design and installation of processing systems. 3-A Accepted Practices encompass Process & Cleaning Systems and Plant Support Systems.

Follow the link at the 3-A SSI web site home page to download a complete current index of documents.

How are 3-A Sanitary Standards and 3-A Accepted Practices developed and maintained?

The responsibility for maintaining existing documents and creating new standards or practices rests with committees comprised of equipment fabricators, processors, regulatory sanitarians, and others. 3-A SSI follows a modern consensus development process, consistent with the Essential Requirements of the American National Standards Institute (ANSI) for standards development and document maintenance. For details on the administration of the 3-A SSI committees and procedures, see this web site under 3-A Sanitary Standards and Committees.

What is the significance of 3-A Sanitary Standards in regulatory inspection requirements?

Food equipment is subject to inspection for general sanitary design and installation. Inspections are routinely conducted under the jurisdiction of federal, state and local regulatory agencies. The 3-A Sanitary Standards and 3-A Accepted Practices are voluntarily applied as suitable sanitary criteria for dairy and food processing equipment. However, 3-A Sanitary Standards and 3-A Accepted Practices enjoy a long history of serving as important references for state and federal regulatory authorities. In addition, 3-A standards have been adopted into some state regulatory codes.

The U.S. Public Health Service (USPHS)/Food and Drug Administration (FDA) role in dairy equipment evaluation is to provide technical assistance to state milk regulatory officials. General requirements for sanitary aspects of dairy equipment and systems are maintained in the Grade A Pasteurized Milk Ordinance (PMO), the official document for the National Conference on Interstate Milk Shipments (NCIMS) (www.fda.gov). While 3-A Sanitary Standards and Practices are not mandatory under the Grade A milk safety program, equipment which meets a current 3-A Sanitary Standard or 3-A Accepted Practice complies with the sanitary design and construction standards of the PMO. Equipment which is not covered by an established 3-A Sanitary Standard or 3-A Accepted Practice will be reviewed utilizing the sanitary design and construction standards of the PMO.

For other food systems, not covered by the PMO, following 3-A Sanitary Standards and Practices may also provide assurance of compliance with current Good Manufacturing Practices (cGMPs) used in FDA inspections as well requirements under Hazard Analysis Critical Control Point (HACCP) regulations.

The U. S. Department of Agriculture (USDA)/Agricultural Marketing Service (AMS) Dairy Division has an approval process for equipment used in dairy facilities subject to their inspection. Under this process, equipment which fully conforms to the criteria set forth in the applicable 3-A Sanitary Standard or 3-A Accepted Practice is accepted as meeting the requirements of the USDA General Specifications. Equipment which is not covered by established 3-A Sanitary Standards or 3-A Accepted Practices will be reviewed by the Dairy Grading Branch utilizing requirements of Section 58.128 of the USDA General Specifications and the USDA Guidelines for the Sanitary Design and Fabrication of Dairy Processing Equipment.

What is the 3-A Symbol and how does it relate to equipment built to a 3-A Sanitary Standard?

Introduced in 1956, the 3-A Symbol is a registered mark used to identify equipment that meets 3-A Sanitary Standards for design and fabrication. Use of the 3-A Symbol is strictly voluntary and is subject to licensing requirements established by 3-A SSI. A manufacturer may receive authorization from 3-A SSI to use the 3-A Symbol.

In 2003, 3-A SSI implemented a Third Party Verification (TPV) inspection and evaluation program for all 3-A Symbol holders. This requirement for independent verification of conformance to a 3-A Standard has substantially enhanced the integrity of the 3-A Symbol. Complete details on the TPV inspection requirement are available on this web site under ‘The 3-A Symbol and Third Party Verification Program’.

So what is the real value of the 3-A Symbol and 3-A Sanitary Standards?

Voluntary use of the 3-A Symbol on dairy and food equipment serves three important purposes:

  • Assures processors that equipment meets sanitary standards;
  • Provides accepted criteria to equipment manufacturers for sanitary design; and
  • Establishes guidelines for uniform evaluation and compliance by sanitarians.

What are the key criteria common to 3-A Sanitary Standards and 3-A Accepted Practices?

The purpose of this ‘primer’ is to introduce and describe some of the specific criteria that are common to 3-A Sanitary Standards and 3-A Accepted Practices. The descriptions below are intended to serve as a starting point for interested readers to seek out deeper knowledge and understanding. This introductory information is not intended to provide authoritative guidance on equipment design/maintenance or regulatory inspection issues. Anyone seeking to design, use, or evaluate equipment to a 3-A Sanitary Standard should rely on professionals with direct experience and proven knowledge.

One of the key references for 3-A SSI committees which draft and develop 3-A Sanitary Standards and 3-A Accepted Practices is the Format and Style Manual for 3-A Sanitary Standards and 3-A Accepted Practices (The Format and Style Manual). A copy of the Format and Style Manual is available from 3-A SSI upon request. A caution to casual readers of this document: The Format and Style Manual is intended as a ‘template’ for those drafting or revising 3-A SSI documents. It includes substantial information on the established format and style conventions for framing these documents, and the generally accepted way of organizing and putting the documents together. But don’t expect detailed lengthy explanations or a ‘short course’ on various subjects in 3-A SSI documents. Nonetheless, the Format and Style Manual does serve as a valuable compilation of criteria that are common to various 3-A SSI documents. Readers who intend to design, use, or inspect equipment built to a 3-A Sanitary Standard should become familiar with these criteria, at a minimum. A comprehensive knowledge of the specific regulatory requirements and the substantial body of engineering and food safety that serve as the foundation for these criteria is essential.

The Format and Style Manual is under ‘continuous maintenance’ and reflects terms and other references that may differ from 3-A SSI documents that were previously published. As general revisions are made to documents, 3-A SSI intends to incorporate elements of the most current Format and Style Manual.

With these caveats, what are some of the key features of 3-A Sanitary Standards and 3-A Accepted Practices?


Every 3-A Sanitary Standard and 3-A Accepted Practice pertains to the sanitary aspects of a specific type of the equipment or system. For 3-A Sanitary Standards, the scope states the function and limits of the equipment and distinguishes the applicability of the document from those found in other standards. For 3-A Accepted Practices, it identifies the nature of the system, the subject or application, and features that are distinguishable from those found in other Accepted Practices. In both cases, the scope is (or should be) concise, but complete enough to define the boundaries of the equipment or system. Very simply, the scope is the statement of intent.

In some cases, the scope may provide restrictions of the 3-A Sanitary Standards or 3-A Accepted Practices. However, the limits and functions of the equipment or system cannot be overemphasized, since the scope defines the criteria necessary for the rest of the document.

Normative References

A series of Normative References are typically named in the document. Provisions of other 3-A Sanitary Standards are frequently referenced in a typical 3-A Sanitary Standard or 3-A Accepted Practice, such as materials requirements or requirements for specific types of equipment (e.g. valves, fittings) . Other standards and references are also named in a 3-A SSI document. These might include materials specifications, regulatory requirements, guidelines and other publicly available specifications.


The Format and Style Manual is a compendium of definitions for terms used in various 3-A Sanitary Standards and 3-A Accepted Practices. These definitions have been painstakingly developed through the consensus process. Why are these definitions and terms so significant? These definitions provide a consistent and uniform reference for various 3-A SSI documents. Even more important, these definitions are the result of a careful consensus development process and the terms reflect a substantial history of use and interpretation among regulatory authorities.

In rare cases, a definition used in a particular document could vary from the Model, but the exception and the reason for the variance will be detailed and limited to the particular document.

A specific 3-A Sanitary Standard or 3-A Accepted Practice will show the terminology and definitions specifically used in the document. The number of definitions depends on the equipment being covered. For example, the standard for membrane modules contains over 80 definitions! All of these definitions were critically needed to cover all the special terminology. Many standards need only 10 to 20 definitions. Just a few of the key definitions include types of cleaning, fittings, inspectable, readily removable, sanitization, surfaces (product contact, nonproduct contact, splash contact, processing air contact and exhaust air contact) and surface modifications, including various treatments and coatings. In addition to greater than 40 more-or-less “standard” definitions found in the Format and Style Manual, other definitions may be specifically needed in certain standards. For example, terminology necessary to describe specific equipment or systems may also be included, especially if they are not standard terminology. Other terms, if needed, rely on standard dictionary references. All additional definitions, when used, are developed through the consensus process.


Many different types of materials are used in the design of 3-A equipment for different applications. Every 3-A Sanitary Standard includes a materials section, which describes those materials acceptable for product contact and those for nonproduct contact. Sanitary specifications dictate allowed materials, with the ultimate criteria being based on the environment of its intended use.

The accepted materials must be suitable for sanitary application, be durable, and be nontoxic (as defined by the Food, Drug, and Cosmetic [FD&C] Act); they may also be a regulated indirect food additive or be demonstrated not to be a food additive or found on the FDA Premarket Notification List (Refer to www.fda.gov).

The benchmark for materials is the AISI 300, excluding 301, Series Stainless Steel or the Alloy Cast Institute (ACI) for cast equivalents. Metals that can be demonstrated to be at least as corrosion resistant as the AISI 300 Series Stainless Steel and are nontoxic and nonabsorbent are also acceptable. Exceptions to the AISI 300 Series Stainless Steel are usually permitted for specific materials reviewed by the 3-A Working Groups when the required function does not allow for the use of the AISI 300 Series Stainless Steel.

Rubber, rubber-like materials, and plastics are the most common material exceptions to stainless steel. Specific 3-A Sanitary Standards have been developed for rubber, rubber-like, and plastic materials. Thus, whenever these materials are used in product contact areas, they must conform to these materials standards. The specific requirements for rubber-like and plastic materials are described at length in othermonographs in this section.

Other permitted materials include the AISI 400 Series Stainless Steel, ceramic, carbon, and plating materials such as chromium or nickel, and other surface- modifying materials and techniques. The exceptions to the AISI 300 Series Stainless Steels must specify certain parts or functions where required, and their use is then limited to those identified parts or functions.


Criteria for the construction and fabrication of 3-A equipment are critically important. All 3-A Sanitary Standards specify fabrication criteria for equipment to be cleanable and to preclude the contamination of the product. Sanitary criteria always include surface finish requirements (generally equivalent to or smoother than a 32 µin. (0.8 µm) Ra ) that is free from imperfections such as pits, folds, and crevices, limitations of radii, draining requirements, accessibility for cleaning and inspection, and design requirements for the proposed method of cleaning including Clean in Place (CIP), Clean out of Place,(COP), or manual cleaning (wet or dry brushing). The integrity of sealed product contact and nonproduct contact surfaces must not be compromised.

In the development of 3-A standards, the usual procedure is to include verbiage in the Appendix that the 32 µin. (0.8 µm) Ra smoothness is generally achieved by provision of a No. 4 finish, and also that 2B cold rolled stainless steel sheets free of defects are considered satisfactory, where appropriate. This means that such inspected 2B sheets may be used for certain applications (e.g. to construct tanks, spray dryers) with subsequent mechanical No. 4 polishing of only the joining welds. Because of light reflectance differences, the polished areas will be highlighted and will look different. However, the fabrication would conform.

The Format and Style Manual details the minimum radii requirements for product contact surfaces. For some equipment, ¼ in. may be specified as the normative minimum radius, but usually with certain exceptions having lesser specified radii. For other equipment, the appropriate normative radius might be 1/8 in., again with some exceptions. Anyone who has manually cleaned dairy or food processing equipment understands that sharp internal angles are hard to clean; gently curved corners make the job much easier.

Conformance to 3-A criteria does not automatically imply compatibility with CIP cleaning since most Standards provide for both manual cleaning and CIP cleaning. CIP cleaning does not preclude regular breakdown of equipment for inspection. Function is not included unless it is necessary for public health reasons such as ingredient addition, product removal, or in the case of aseptic equipment, automatic shutdown.

Optional Sections

A 3-A Sanitary Standard may include other sections, when needed. These optional sections include:

  • Special Considerations—This Section is used where unique fabrication or installation requirements are necessary, such as where HTST pasteurization systems are integral with spray dryer systems or evaporators.
  • Installation—This section is optional for standards but required for most practices. Installation criteria, when required, may include but is not limited to the Grade A PMO or other regulatory requirements; proper juxtaposition of equipment, floor, wall or ceiling clearance; and interconnections and hard wiring for required regulatory controls. In 3-A Accepted Practices this section is in the body of the document; in 3-A Sanitary Standards, if used, it may be in either the body or the Appendix.
  • Appendix—The Appendix is an advisory or informative section of 3-A Sanitary Standards or 3-A Accepted Practices unless specifically cited in the Fabrication Section as requiring conformance. Although generally optional, this section is usually found in 3-A documents. The Appendix usually includes references to stainless steel materials and provides methods for achieving and measuring the required product contact surface finish. It may also include other advisory information useful for proper construction, material specifications, installation, cleaning and diagrams of the equipment or system covered by the 3-A Sanitary Standard or 3-A Accepted Practice.

Even when not considered as normative by reference, regulatory agencies under their procedures and authority may use the non-normative Appendix information during inspections if no other guidance on Appendix items is available from the fabricator or the processor. The Appendix may also contain representative diagrams of equipment or systems and a suggested format for the Engineering Design and Technical Construction File (EDTCF). The EDTCF is to be maintained by the fabricator for all products, assemblies and sub-assemblies as evidence of conforming to 3-A Sanitary Standards or 3-A Accepted Practices. The maintenance of this file is required for authorization to display the 3-A Symbol.