O-RINGs Approvals | Design Simply explained

List of the most important O-ring approvals

Gas pipes, systems in food production or drinking water supply: O-rings are used in numerous sensitive areas of application.

If the seals fail, this not only results in a machine malfunction and the problems directly associated with it. In the worst case, there is a risk to the integrity of people and the environment.

This is the case, for example, when potentially contaminated food enters circulation.

To minimize such risks for all parties involved, there are industry and application-specific approvals for O-rings. These legally binding regulations specify technical requirements for the sealing elements.

Users should be familiar with the relevant O-ring approvals for their area.


Type of approval



Food & pharma


3-A Sanitary Standard

Food & pharma


USP Class VI

Food & pharma


BSE/TSE Freedom

Food & pharma


Elastomer guideline (KTW)

Drinking water



Drinking water



Drinking water

Great Britain


Drinking water



Oil & Gas






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#1 O-ring approvals: Food and pharma

Various organizations place requirements on O-rings that are involved in the food production process.

Some of them refer to different areas of application, but compliance with them is always the basic condition for the marketing of food products in the respective area of application.

FDA stands for the US Food and Drug Administration.

This institution publishes a list of elastomer materials that are approved for use in all phases of food production. High temperatures, hot steam up to 150 °C and cleaning agents are the most important factors for stressing the O-rings in this area.

These are the central requirements of the FDA for O-rings:

  • No toxic effect
  • No carcinogenic effect
  • Extraction within the permissible limits

The FDA regulations also apply to drugs and medical devices. Although it is a national authority, the FDA regulations are applied globally.

FDA conformity is therefore very important for the use of O-rings.

Important detail: The FDA itself does not grant approval for specific materials. Instead, it is up to the O-ring manufacturer to prove conformity.

3-A Sanitary Standard
Unlike the FDA, the publisher of the 3-A Sanitary Standards is not an authority, but an independent organization.

Its requirements also relate to the food and pharmaceutical sectors. The focus for O-rings is primarily on systems and devices for processing dairy products.

By passing the relevant extraction tests, O-ring materials prove their suitability for this area of application.

USP Class VI
The United States Pharmacopeia (USP) regulates the requirements for medical and pharmaceutical technology products.

However, it also refers to the ingredients of food. The focus here is on biocompatibility. This also applies to plastics, which are used as the base material for O-rings.

Tests show the extent to which certain materials react with the living organism. To this end, the organization tests the reaction of the organism to direct and indirect contact as well as to the injection of extracts from the sealing material.

In particular, it is important to prevent materials from releasing harmful substances in the body or causing a rejection reaction.

The O-ring material is categorized into one of six classes based on its reactivity. Class 6 is the category with the highest requirements. O-rings for use in pharmaceutical technology must meet these criteria.

BSE/TSE Freedom
BSE is a brain disease that affects cattle (bovine spongiform encephalopathy).

It can also occur in humans and is therefore classified as a transmissible spongiform encephalopathy (TSE). This is a group of infectious diseases of the nervous system that have a fatal course.

Sealing materials for the food industry must therefore be free from additives of animal origin. Many technical documents also contain the abbreviation ADI-free.

Gasket manufacturers must check their portfolio of materials for ingredients and additives with the involvement of ADI (Animal Derived Ingredients) and declare that they are ADI-free.


#2 O-ring approvals: Potable water

O-rings for drinking water systems are subject to their own specific guidelines, which are independent of the food approvals listed above.

This means that drinking water is generally subject to even stricter regulations than all other foods.

Elastomer guideline (KTW)
The KTW approval is a health standard for plastic components of drinking water systems that is valid in Germany.

It applies to all devices, components and materials that come into contact with drinking water during use and is intended to prevent all contamination – including through seals.

The Federal Environment Agency has published a guideline on the hygienic assessment of elastomers in contact with drinking water (elastomer guideline). It consists of three main sections:

  • Positive list of usable raw materials for elastomer production
  • Prescribed test procedures
  • Test values to be complied with

The German edition of the drinking water regulations is legally binding. However, it is not the only relevant regulation internationally. There are also the British standard WRAS, the American NSF61 and the Austrian Ö-Norm, which are frequently encountered in practice.

In addition to KTW approval, DVGW W270 approval must also be obtained in the area of application of the German Drinking Water Ordinance.

DVGW is the abbreviation of the German Technical and Scientific Association for Gas and Water. DVGW Code of Practice W270 describes test methods for determining the extent to which microorganisms multiply on organic sealing materials.

Independent certification bodies issue the test certificates in accordance with DVGW W270 and KTW.

The British standard BS 6920 for seals suitable for drinking water is known primarily under the abbreviation WRAS (Water Regulations Advisory Scheme).

The regulations apply not only to O-rings, but to all non-metallic components that come into contact with drinking water.

The test criteria for materials are similar to those in the German Elastomer Guideline and DVGW W270 and are intended to prevent undesirable adverse effects on drinking water:

  • Influencing odor and taste
  • Visual change
  • Microbial growth
  • Leaching of the gasket material

NSF-61 material certification is an American standard for drinking water system components.

The National Sanitation Foundation regulation also covers O-rings and other sealing elements made of EPDM, silicone, NBR and other elastomers.

As with other national regulations, the focus here is also on minimizing the impact on drinking water.

#3 O-ring approvals: Gas

Gas is a particularly safety-critical medium.

Similar to drinking water, there are therefore very specific requirements for suitable sealing elements for gas-conducting systems.

With regard to gas consumption and gas supply equipment, the DVGW specifies the rules for suitable materials.

They must meet the requirements of DIN EN 549 (gas appliances and gas systems) or DIN EN 682 (supply lines) for elastomer materials in the gas sector. The conformity tests are carried out by DVGW-recognized bodies.

NORSOK M-710 is a standard from the Norwegian oil and gas industry.

The operating conditions of such industrial systems are characterized by very aggressive media, high pressure and a wide temperature range. This favors several common damage mechanisms on O-rings.

As the leading internationally recognized standard, the M-710 standard stands for O-rings that are particularly resistant to the usual media and, above all, the strongly changing pressure load.

#4 O-ring approvals: Oxygen

Pure oxygen for technical and medical applications must be protected from interaction with other media or the system components themselves.

Oxygen enrichment represents a considerable fire hazard. In addition, the combination of oxygen and heat causes some O-ring materials to age very quickly.

O-ring materials for oxygen fittings fall under the regulatory scope of the Federal Institute for Materials Research (BAM). 

As a globally recognized testing laboratory, it tests elastomer materials for their reaction in contact with liquid and gaseous oxygen. Suitable materials are published in list M 034-1 of the German Social Accident Insurance Institution for the raw materials and chemical industry (BG RCI). 

For each material with the manufacturer-specific material designation, the list specifies maximum limit values for pressure and temperature.

#5 O-ring approvals provide safety

The abbreviation “RoHS” stands for “Restriction of Hazardous Substances” and refers to an EU directive to restrict the use of certain hazardous substances in electronic devices and components. 

This directive applies to all manufacturers and distributors operating in the EU or exporting to the EU. 

The RoHS Directive restricts the use of six specific hazardous substances in electronic devices and components: Lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE).

The abbreviation “REACH” stands for “Registration, Evaluation, Authorization and Restriction of Chemicals” and refers to an EU regulation for the regulation of chemical substances that are manufactured, imported or sold in the EU. 

REACH requires companies that produce or import chemical substances to register and evaluate these substances and, if necessary, to obtain authorization. 

The aim of REACH is to protect human health and the environment from the possible effects of chemicals and at the same time to maintain the competitiveness of the European chemical industry.

Conflict material
The abbreviation “conflict material” refers to raw materials such as tantalum, tin, tungsten and gold, which originate from conflict regions and can contribute to the financing of armed conflicts and human rights violations. 

However, the abbreviation itself is not commonly used; the term “conflict commodities” is often used. There are various international initiatives and regulations to curb trade in conflict minerals, such as the Dodd-Frank Act in the USA or the EU regulation on conflict minerals. 

Every industry has its own specific requirements for sealing elements. 

But all users have one goal in common: O-rings must function reliably so that technical devices can work stably and efficiently.

Companies that use such raw materials are increasingly being asked to monitor their supply chains and ensure that they do not contain conflict minerals.

O-Rings with the appropriate approvals are an important means of achieving this. They guarantee the basic suitability of the O-ring material for the respective application and the high quality of the materials. Users should therefore pay particular attention to the O-ring approvals in all regulated areas. 

The O-ring suppliers indicate which approvals they have for each compound number in their range.

“I am convinced that we should share our knowledge with the world. I hope I have been able to answer all your questions. If you have any further questions, please feel free to contact us at any time. We will be happy to help you.”

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Luke Williams

Lord of the O-rings
Author of the sealing academy

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