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Three ASME A13.1 pipe markers.

Pipe marking is the used to identify the contents, properties and flow direction of fluids in piping. Marking assists personnel to identify the correct pipes for operational, maintenance or emergency response purposes. Pipes are marked by labels, typically color coded, to identify the use, contents and flow direction.


Pipes are used extensively in commercial and industrial buildings and on industrial plant (e.g. oil refineries) to transfer fluids between items of plant and equipment.[1] Positive identification assists operations personnel to correctly identify plant when carrying out routine or maintenance activities, and for emergency personnel when responding to emergencies. Pipe marking is particularly important for identification where pipes run along pipe racks, through walls and bulkheads and through floors.[2]

A range of corporate, national and international codes, standards and regulations are in use around the world.

ANSI/ASME Standards

In the United States, Occupational Safety and Health Administration regulations recommend following American Society of Mechanical Engineers Standard A13.1-2015 - Scheme for the Identification of Piping Systems.[3]

The standard states that labels should be placed where easily viewed by a person standing near the pipe at any of the following points:[4]

A13.1-1996 [4]
Meaning Background Color Text Color Example
Hazardous materials[a] Safety Yellow Black Acetylene
Non-hazardous liquids Safety Green White Stormwater
Non-hazardous gases Safety Blue White Nitrogen
Firefighting materials Safety Red White Sprinkler Water
Meaning Background Color Text Color Example
Flammables[b] & Oxidizers[c] Safety Yellow Black Acetylene
Combustible Fluids[d] Safety Brown White Lubricating Oil
Toxic and Corrosives Safety Orange White Ammonia
Water Safety Green White Stormwater
Compressed air/Non-hazardous gases Safety Blue White Compressed Air
Firefighting materials Safety Red White Sprinkler Water
Custom - Defined by user Safety Purple White Fluid Name
Custom - Defined by user Safety Grey White Fluid Name
Custom - Defined by user White Black Fluid Name
Custom - Defined by user Black White Fluid Name

2015 revisions

A 2015 style pipe marker with GHS signal word and symbols.

2015 revisions added oxidizing materials to the existing 'Flammables' classification. The other major change allowed and encouraged labels to incorporate the GHS signal word, hazard pictograms, and hazard statements. This addition helped identify additional dangers when dealing with materials that fit into multiple categories, like hydrogen sulfide, which is both flammable and toxic.[4]

IIAR Bulletin #114

IIAR Bulletin 114 pipe marker for a low-temperature recirculated suction (LTRS) line, where both liquid and vapor are present[6]

In 2014, the International Institute of Ammonia Refrigeration introduced a specialized label design for use when marking pipes associated with refrigeration systems using ammonia, including information such as the physical state, pressure and purpose in the system.[6]

NFPA 99C 2002

The National Fire Protection Association have a special labeling system in the standard for Health Care Facilities, such as hospitals and dentistry offices. This standard puts more emphasis on gases found in Medical gas supply systems, which consist of both oxidizing gases and gases that displace oxygen.[7]

Gas Background Color Text Color
Carbon Dioxide Gray Black or White
Helium Brown White
Medical Air Yellow Black
Oxygen Green White[e]
Oxygen/Carbon Mixtures Green White
Nitrogen Black White
Nitrous Oxide Blue White
Waste Anesthetic Gas Disposal Purple White
Medical Surgical Vacuum White Black
Non-Medical Air Yellow/White Diagonal Striped Black
Non-medical and Level 3 Vacuum Black/White Diagonal Striped Black (In box)
Laboratory Air Yellow/White Checkerboard Black
Laboratory Vacuum Black/White Checkerboard Black (In box)
Instrument Air Red White

United Kingdom Regulations

In the United Kingdom there are three principal regulations that mandate the marking of equipment and piping:

The regulations require that vessels containing hazardous substances together with the pipes containing or transporting such substances must be labelled or marked with the relevant hazard pictograms or pipe marking. The labels used on pipes must be positioned visibly in the vicinity of the most hazardous points, such as valves and joints; at both sides of bulkheads and floor penetrations; and at reasonable intervals.

The regulations do not specify a specific marking system, but BS EN ISO 1710 Graphical symbols — Safety colours and safety signs is often used.

BS EN ISO 1710

A widely used British (BS), European (EN) and International (ISO) standard for marking equipment is:

The Standard stipulates the colours to be used. These are as follows:[2]

BS EN ISO 1710 Basic identification colours for pipes
Contents Colour BS 4800 colour
Water Green 12 D 45
Steam Silver-grey 10 A 03
Oils Brown 06 C 39
Gases Yellow Ochre 08 C 35
Acids and Alkalis Violet 22 C 37
Air Light Blue 20 E 51
Other liquids Black 00 E 53
Electrical & Ventilation Orange 06 E 51

In addition to the basic colours, certain safety colours are used:

BS EN ISO 1710 Safety colours for pipes
Safety service Colour BS 4800 colour
Fire fighting Red 04 E 53
Warning Yellow 08 E 51
Fresh water Auxiliary Blue 18 E 53
User defined User defined

The arrangement of markings is for the safety colour to be between bands of the basic colour.[2]

Firewater service would be:

Basic marking of firewater piping in accordance with BS EN ISO 7010

The pipe contents must be identified adjacent to the banding.[2] This can be done by giving either:

The direction of flow should also be identified near the banding.[2]

Examples using this system are as shown.

Examples of pipe marking using BS EN ISO 7010

Ships and marine facilities (ISO 14726)

Ships and marine facilities must conform to an international standard for piping systems identification. This is ISO 14726:2008 Ships and marine technology — Identification colours for the content of piping systems.[10]

This is a two-colour banded marking system. The main colour shows what the fluid is being used for. This is on either side of the secondary colour which indicates what the substance actually is. The main colours are as follows:[10]

International Standard ISO 20560-1

International Standard ISO 20560-1 Safety information for the content of piping systems and tanks — Part 1: Piping systems was intended to replace the variety of regulations and standards across countries and regions. Basic identification colours and warning symbols identify the pipe contents and any hazards.[11]

Pipe markers consists of 4 basic elements:

Colours and substances are typically as follows:[11]

ISO 20560-1 Colours and substances
Substance Background colour Text colour
Hazardous substances Yellow Black
Gas (liquid or gaseous) Grey White
Liquids & solids (powder/granulate) Black White
Acids Orange Black
Alkalis Violet White
Fire fighting medium Red White
Water Green White
Air Blue White

See also


  1. ^ Explosives, flammables, corrosives, toxic, radioactive, extreme pressures/temperatures.
  2. ^ Flash point below 100 °F (38 °C; 311 K).[5]
  3. ^ Oxidizers were added in 2015 update.[5]
  4. ^ Fluids that can burn, but are not considered 'flammable', flash point at or above 100 °F (38 °C; 311 K).[5]
  5. ^ Background & Text color can be reversed.


  1. ^ a b "Safe use of work equipment" (PDF). Retrieved 12 February 2022.
  2. ^ a b c d e "Pipe marking solutions to meet British Standard 1710 (BS 1710)". October 2018. Retrieved 12 February 2022.
  3. ^ Occupational Safety & Health Administration (November 2016). "1910.261 - Pulp, paper, and paperboard mills". Retrieved 21 March 2019. 1910.261(a)(3)(ii) Scheme for the Identification of Piping Systems, A13.1—1956.
  4. ^ a b c d Brimar Industries. "ANSI/ASME A13.1 2015" (PDF). Archived from the original (PDF) on 21 March 2019. Retrieved 21 March 2019.
  5. ^ a b c NASA (17 November 2017). "GSFC-STD-8006 - Safety Standard for Ground piping Systems Color Coding and Identification". Retrieved 21 March 2019.
  6. ^ a b International Institute of Ammonia Refrigeration. "Guidelines for: Identification of Ammonia Refrigeration Piping and System Components" (PDF). Archived from the original (PDF) on 21 March 2019. Retrieved 21 March 2019.
  7. ^ Craftmark Pipe Markers. "NFPA 99C 2002" (PDF). Archived from the original (PDF) on 21 March 2019. Retrieved 21 March 2019.
  8. ^ "The GB CLP Regulation". Retrieved 12 February 2022.
  9. ^ "The Health and Safety (Safety Signs and Signals) Regulations 1996" (PDF). Retrieved 12 February 2022.
  10. ^ a b "ISO 14726". Retrieved 13 February 2022.
  11. ^ a b "ISO 20560". Retrieved 14 February 2022.