Hazard Sign Symbols Explained: CLP Pictograms & UK Workplace Signboards

UK hazard sign symbols fall into two legally distinct systems: GHS/CLP chemical pictograms that must appear on hazardous substance containers and labels, and workplace safety signboards governed by the Health and Safety (Safety Signs and Signals) Regulations 1996. Both are legally required — but for different situations, governed by different instruments, and distinguished by shape, colour, and purpose. This page explains both systems, their legal triggers, and exactly how to apply them.

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1. The Legal Trigger: When Must You Provide Hazard Signs?

Signs are not a default first response to every risk. Under the Health and Safety (Safety Signs and Signals) Regulations 1996, regulation 4, an employer must provide appropriate safety signs only after the risk assessment required by Management of Health and Safety at Work Regulations 1999 reg 3 shows that risks cannot be avoided or adequately reduced by other means — such as engineering controls or safe working procedures. (Health and Safety (Safety Signs and Signals) Regulations 1996, regulation 4 — Provision and maintenance of safety signs)

That risk assessment is the foundation. Under Management of Health and Safety at Work Regulations 1999 reg 3, every employer must make a suitable and sufficient assessment of the risks to which employees are exposed at work. (Management of Health and Safety at Work Regulations 1999, reg 3 — risk assessment) The HSE describes this as a five-step process: identify hazards, assess risks, control risks, record findings, and review controls. (HSE — Risk assessment: steps needed to manage risk) Signage sits at the control stage — a last-resort communicative control, not a substitute for physical risk reduction.

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2. Two Distinct Systems: CLP Pictograms vs. Workplace Signboards

This is the distinction many practitioners miss, and conflating the two leads to compliance gaps.

Feature	CLP Chemical Pictogram	Workplace Safety Signboard
Governing instrument	Retained CLP Regulation (EC) 1272/2008	Health and Safety (Safety Signs and Signals) Regulations 1996
Shape	Diamond (square on point)	Varies by category (round, triangle, rectangle/square)
Border colour	Bold red	Varies (red, yellow/black, blue, green, red)
Background	White	Varies by category
Appears on	Chemical labels, containers, visible pipes	Walls, posts, doors, equipment in the workplace
Purpose	Communicates the intrinsic chemical hazard	Communicates a workplace area or equipment risk
Who places it	Supplier (on label) or employer (on container at work)	Employer

Under the retained CLP Regulation (EC) 1272/2008, Article 19, the label shall include the relevant hazard pictogram(s) intended to convey specific information on the hazard concerned, and pictograms shall fulfil the requirements laid down in section 1.2.1 of Annex I and in Annex V. (Retained CLP Regulation (EC) 1272/2008 — classification, labelling and packaging, Article 19 — Hazard pictograms)

A CLP pictogram on a container tells you what the substance inherently is. A yellow triangle on a wall tells you there is a hazard in that area or location. They can co-exist — and often must.

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3. The CLP Hazard Pictograms: Complete Quick-Reference Table

The CLP Regulation assigns specific hazard pictogram(s) to each hazard class. The table below covers the core pictograms. Note that a single substance label may carry more than one pictogram, and a single pictogram can cover multiple hazard classes. The pictogram relevant for each specific classification is set out in the tables in Annex I of the CLP Regulation. (Retained CLP Regulation (EC) 1272/2008 — Article 19)

Format note: All CLP pictograms share the same format — a black symbol on a white background inside a red diamond border. This is legally distinct from the yellow-triangle workplace warning signboard, even where the imagery is similar.

GHS Code	Common Name	Hazard Classes Covered	Signal Word Tier	Equivalent Workplace Warning Signboard (Sch 1, reg 3)
GHS01	Exploding bomb	Explosives; self-reactive substances; organic peroxides (where applicable)	Danger	Explosive material
GHS02	Flame	Flammable gases, liquids, solids, aerosols; self-heating substances; pyrophoric substances; self-reactive substances; organic peroxides (where applicable)	Danger or Warning (depends on category)	Flammable material or high temperature
GHS03	Flame over circle	Oxidising gases, liquids, solids	Danger or Warning	Oxidant material
GHS04	Gas cylinder	Gases under pressure (compressed, liquefied, dissolved, refrigerated liquefied)	Warning	No direct equivalent — use CLP pictogram
GHS05	Corrosion	Corrosive to metals; skin corrosion; serious eye damage	Danger or Warning	Corrosive material
GHS06	Skull and crossbones	Acute toxicity (oral, dermal, inhalation) — severe categories	Danger	Toxic material
GHS07	Exclamation mark	Acute toxicity (lower severity); skin/eye irritation; skin sensitisation; specific target organ toxicity (single exposure); respiratory tract irritation; narcotic effects	Warning	No direct equivalent — use CLP pictogram
GHS08	Health hazard (silhouette with starburst)	Respiratory sensitisation; carcinogenicity; reproductive toxicity; specific target organ toxicity (repeated exposure); aspiration hazard; germ cell mutagenicity	Danger or Warning	No direct equivalent — use CLP pictogram
GHS09	Dead tree and fish	Hazardous to the aquatic environment	Warning (mostly)	No direct equivalent — use CLP pictogram

Key rule: Where no equivalent workplace warning signboard exists in Schedule 1 Part II of the Safety Signs and Signals Regulations 1996, the employer must use the relevant CLP hazard pictogram from Annex V of the CLP Regulation to mark storage areas. (Health and Safety (Safety Signs and Signals) Regulations 1996, SCHEDULE 1 (part 6))

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4. The 5 Categories of Workplace Safety Signboard: Shape, Colour, and Legal Specifications

Under the Health and Safety (Safety Signs and Signals) Regulations 1996, Schedule 1 sets out five distinct categories of workplace signboard, each distinguished by a specific shape and colour combination. (Health and Safety (Safety Signs and Signals) Regulations 1996, regulation 3 — Signboards to be used)

Red = prohibition/danger/fire-fighting; Yellow = warning; Blue = mandatory; Green = emergency/first-aid. (Health and Safety (Safety Signs and Signals) Regulations 1996, SCHEDULE 1 (part 2))

4.1 Prohibitory Signs

• Shape: Round
• Design: Black pictogram on white background, red edging and diagonal line — red part must be at least 35% of sign area
• Examples: No smoking; Smoking and naked flames forbidden; No access for unauthorised persons; Do not extinguish with water

4.2 Warning Signs

• Shape: Triangular
• Design: Black pictogram on yellow background with black edging — yellow part must be at least 50% of sign area
• Examples: Flammable material or high temperature; Explosive material; Toxic material; Corrosive material; Danger: electricity; Biological risk; Oxidant material; General danger; Overhead load; Drop

4.3 Mandatory Signs

• Shape: Round
• Design: White pictogram on blue background — blue part must be at least 50% of sign area
• Examples: Eye protection must be worn; Safety helmet must be worn; Ear protection must be worn; Respiratory equipment must be worn; Safety harness must be worn

4.4 Emergency Escape or First-Aid Signs

• Shape: Rectangular or square
• Design: White pictogram on green background — green part must be at least 50% of sign area
• Examples: Emergency exit/escape route; First-aid post; Stretcher; Safety shower; Eyewash; Emergency telephone for first-aid or escape

4.5 Fire-Fighting Signs

• Shape: Rectangular or square
• Design: White pictogram on red background — red part must be at least 50% of sign area
• Examples: Fire hose; Ladder; Fire extinguisher; Emergency fire telephone (Health and Safety (Safety Signs and Signals) Regulations 1996, SCHEDULE 1 (part 6))

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5. Signal Words 'Danger' and 'Warning': What the CLP Severity Tiers Mean

Under the CLP Regulation, chemical labels carry one of two signal words. These words communicate the relative severity of the hazard:

• 'Danger' — assigned to the more severe hazard categories within a given hazard class
• 'Warning' — assigned to less severe categories within a hazard class

Where a substance is classified in multiple hazard classes that would each trigger a signal word, only one signal word appears on the label: where 'Danger' would apply for any classification, 'Danger' is used and 'Warning' is not shown.

In practice, this tells a site supervisor at a glance how seriously to treat the substance. A container labelled 'Danger' with GHS06 (skull and crossbones) represents an acutely toxic substance in a severe category. The same GHS07 (exclamation mark) symbol always carries 'Warning', indicating a lower-severity acute hazard — but one that still requires appropriate controls and storage marking.

Signal words are specific to CLP chemical labelling. Workplace safety signboards under the Safety Signs and Signals Regulations 1996 do not use signal words — they communicate via colour, shape, and pictogram alone.

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6. The Old Orange Symbols: Are They Still Compliant?

Before the current CLP system, hazardous substances in the UK carried square orange-background symbols — the familiar orange square with a black pictogram and a written hazard description such as 'Toxic' or 'Irritant'. These have been replaced by the current GHS-aligned CLP format: a black symbol inside a red diamond border on a white background.

The pre-CLP orange symbols are no longer compliant with the current labelling framework. Any container in your workplace still bearing only orange-square labelling is not meeting the requirements of the retained CLP Regulation. It is also worth noting that the Safety Signs and Signals Regulations 1996 reference the CLP Regulation's Annex V pictograms as the standard — not the former orange-square format. Employers should audit their stock, storage, and any transferred containers to ensure all labels reflect the current CLP pictogram format.

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7. UNIQUE ASSET — Decision Tree: Which Hazard Symbol Regime Applies?

Use this decision tree to determine which symbol system applies to any given situation on site.

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START: You have identified a hazard. Which symbol regime applies?
│
├─► Is the hazard a CHEMICAL SUBSTANCE or MIXTURE classified under CLP?
│   │
│   YES ──► CLP pictogram(s) MUST appear on the container label and on
│   │       any visible pipe carrying the substance.
│   │       [Source: Safety Signs and Signals Regulations 1996, Sch 1 Part III]
│   │
│   │       └─► Is the substance stored in significant quantities in a
│   │           room, area, or enclosure?
│   │           │
│   │           YES ──► A suitable WARNING SIGNBOARD (triangular, yellow)
│   │                   from Sch 1 reg 3.2 must also mark the entry point.
│   │                   If no equivalent warning signboard exists in Sch 1,
│   │                   use the CLP pictogram from Annex V instead.
│   │                   [Source: Safety Signs and Signals Regulations 1996, Sch 1 Part III, para 12]
│   │
│   NO ──► Is the hazard a WORKPLACE AREA OR EQUIPMENT RISK (not chemical-specific)?
│           │
│           YES ──► Apply the appropriate SAFETY SIGNBOARD under the Safety
│                   Signs and Signals Regulations 1996:
│                   • Area prohibition → round, red/white/black diagonal
│                   • Area warning → triangular, yellow/black
│                   • PPE requirement → round, blue/white
│                   • Escape/first-aid → rectangular/square, green/white
│                   • Fire-fighting → rectangular/square, red/white
│
├─► Is the container used only BRIEFLY or does its contents change FREQUENTLY?
│   │
│   YES ──► CLP container labelling may not be required IF alternative adequate
│           measures (information and/or training) provide the same level of
│           protection. [Source: Safety Signs and Signals Regulations 1996, Sch 1 Part III]
│           Consider: is training alone genuinely equivalent? If uncertain, label.
│
└─► GENERAL DANGER sign — when can it be used for substances?
    ONLY where the sign indicates stores of a NUMBER of hazardous substances
    or mixtures together. It must NOT be used to warn about a single specific
    hazardous substance or mixture.
    [Source: Safety Signs and Signals Regulations 1996, regulation 2 — Conditions of use]

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Worked Scenario: Construction Site Acetone Storage

Situation: A construction site stores acetone in a dedicated storage room. Acetone is classified as a flammable liquid and has acute toxicity (category 4, oral route) under CLP.

Step 1 — Container label: The acetone container must carry CLP pictograms. Given its classifications:

• GHS02 (Flame) — flammable liquid
• GHS07 (Exclamation mark) — acute toxicity category 4

The signal word on the label will be 'Danger' because the flammable liquid classification in its category triggers 'Danger'. Where both 'Danger' and 'Warning' would otherwise apply from different classifications, 'Danger' takes precedence and 'Warning' is omitted from the label.

Step 2 — Storage room entrance signboard: The storage room holds significant quantities of a hazardous substance. A warning signboard (triangular, black pictogram on yellow, yellow ≥50% of sign area) for 'Flammable material or high temperature' must be displayed at the room entrance. This is the equivalent workplace warning sign from Schedule 1, regulation 3.2 for the flammable hazard. (Health and Safety (Safety Signs and Signals) Regulations 1996, regulation 3 and SCHEDULE 1 (part 3))

Step 3 — The 'General danger' sign: The single-substance-specific flammable warning sign is required here. The 'General danger' sign cannot be substituted for a substance-specific sign at a single-substance storage point. (Health and Safety (Safety Signs and Signals) Regulations 1996, regulation 2 — Conditions of use)

Step 4 — If multiple substances are stored together: If the room stores acetone alongside other hazardous substances, the 'General danger' sign may be used to indicate the mixed-hazard store — but individual containers must still carry their CLP labels.

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8. Where and How to Display Hazard Signs: Placement, Lighting, and the 'Remove When No Longer Needed' Rule

Signboards must be installed at a suitable height and in a position appropriate to the line of sight, accounting for obstacles. For general area hazards, signs go at the access point; for specific hazards or objects, in the immediate vicinity. Where natural light is poor, phosphorescent colours, reflective materials, or artificial lighting must be used. (Health and Safety (Safety Signs and Signals) Regulations 1996, SCHEDULE 1 (part 4))

Critically, the signboard must be removed when the situation to which it refers ceases to exist. (Health and Safety (Safety Signs and Signals) Regulations 1996, regulation 2 — Conditions of use) A warning sign left in place after a hazard is resolved creates false hazard communication — and may cause workers to ignore signage elsewhere through sign fatigue.

Equally, placing too many signs too close together must be avoided. The effectiveness of a sign must not be adversely affected by the presence of another emission source of the same type which interferes with visibility or audibility. (Health and Safety (Safety Signs and Signals) Regulations 1996, SCHEDULE 1 (part 2))

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9. Maintenance and Inspection Obligations

Depending on requirements, signs and signalling devices must be cleaned, maintained, checked, repaired, and if necessary replaced on a regular basis to ensure they retain their intrinsic and/or functional qualities. (Health and Safety (Safety Signs and Signals) Regulations 1996, SCHEDULE 1 (part 2)) A faded, cracked, or illegible sign is not a compliant sign — regardless of how recently it was installed.

For illuminated signs: signs requiring some form of power must be provided with a guaranteed emergency supply in the event of a power cut, unless the hazard has thereby been eliminated. (Health and Safety (Safety Signs and Signals) Regulations 1996, SCHEDULE 1 (part 3))

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10. Special Cases: Impaired Workers, Illuminated Signs, and Multi-Substance Storage

Impaired workers: If the hearing or sight of workers is impaired — including impairment caused by wearing personal protective equipment — measures must be taken to supplement or replace the signs concerned. (Health and Safety (Safety Signs and Signals) Regulations 1996, SCHEDULE 1 (part 3)) Workers in hearing protection zones or eye protection zones may not be able to rely solely on visual or audible signals. Supplementary controls (buddy systems, physical barriers, vibrating alerts) should be considered.

Illuminated signs: The triggering of an illuminated sign indicates when the required action should start; the sign must remain activated for as long as the action requires and must be reactivated immediately after use. Illuminated signs must be checked to ensure they function correctly before being put into service and subsequently at sufficiently frequent intervals. (Health and Safety (Safety Signs and Signals) Regulations 1996, SCHEDULE 1 (part 3))

Multi-substance storage rooms: Areas, rooms, or enclosures used for the storage of significant quantities of hazardous substances or mixtures must be indicated by a suitable warning sign from Schedule 1 Part II (reg 3.2), or marked with CLP pictograms where no equivalent sign exists. (Health and Safety (Safety Signs and Signals) Regulations 1996, SCHEDULE 1 (part 3)) This is the one situation where the 'General danger' sign may be used for hazardous substances — only where it indicates a store containing multiple different hazardous substances or mixtures. (Health and Safety (Safety Signs and Signals) Regulations 1996, regulation 2 — Conditions of use)

Brief-use containers: Container labelling obligations under Schedule 1 Part III do not apply to containers used at work for brief periods, or to containers whose contents change frequently, provided that alternative adequate measures — particularly information and/or training — guarantee the same level of protection. (Health and Safety (Safety Signs and Signals) Regulations 1996, SCHEDULE 1 (part 6)) This exemption is narrow: the burden of demonstrating equivalence sits with the employer.

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11. Compliance Checklist: 10 Checks Drawn Directly from the Regulations

Review and adapt this checklist to your specific site, task, and contractor arrangements. Tick each item only after verifying against your actual site conditions.

#	Check	Primary Source
☐ 1	Signs are installed at a suitable height and appropriate to the line of sight, accounting for obstacles	Safety Signs and Signals Regulations 1996, SCHEDULE 1 (part 4)
☐ 2	Where natural light is poor, phosphorescent colours, reflective materials, or artificial lighting are used	Safety Signs and Signals Regulations 1996, SCHEDULE 1 (part 4)
☐ 3	Signs are cleaned, maintained, checked, repaired, and replaced on a regular basis	Safety Signs and Signals Regulations 1996, SCHEDULE 1 (part 2)
☐ 4	Illuminated signs have a guaranteed emergency power supply unless the hazard is eliminated on power loss	Safety Signs and Signals Regulations 1996, SCHEDULE 1 (part 3)
☐ 5	Signs are removed when the situation to which they refer ceases to exist	Safety Signs and Signals Regulations 1996, regulation 2 — Conditions of use
☐ 6	The 'General danger' sign is not used for a single specific hazardous substance (only for mixed-substance stores)	Safety Signs and Signals Regulations 1996, regulation 2 — Conditions of use
☐ 7	Containers for hazardous substances carry CLP pictogram labels (except where the brief-use/frequent-change exemption genuinely applies with equivalent information/training in place)	Safety Signs and Signals Regulations 1996, SCHEDULE 1 (part 6)
☐ 8	Where workers' hearing or sight is impaired (including by PPE), supplementary or replacement measures are in place	Safety Signs and Signals Regulations 1996, SCHEDULE 1 (part 3)
☐ 9	Hazardous substance storage rooms are marked with a suitable warning signboard from reg 3.2, or with the CLP pictogram where no equivalent signboard exists	Safety Signs and Signals Regulations 1996, SCHEDULE 1 (part 3)
☐ 10	Signs are not placed so close together that they obscure each other's meaning	Safety Signs and Signals Regulations 1996, SCHEDULE 1 (part 2)

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12. How RamsDocs Helps You Embed Hazard Symbol Compliance

Every RAMS document and risk assessment produced with RamsDocs is built around the control hierarchy — with signage correctly positioned as a communicative control layer, not a substitute for engineering or procedural controls. Our templates prompt you to:

• Record which CLP pictograms are present on substances used in the task
• Identify which workplace safety signboards the risk assessment triggers
• Note sign placement, lighting conditions, and maintenance review intervals
• Flag when impaired-worker supplementary measures are needed

RamsDocs outputs are designed to be PC review-ready and to reduce RAMS rework — but every document must be reviewed and adapted to your specific site, task, and contractor by a competent person before use.

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Frequently Asked Questions

What are the GHS/CLP hazard pictograms used on chemical labels in the UK? The CLP Regulation assigns hazard pictograms to specific hazard classifications. The core pictograms cover: explosives (GHS01); flammables (GHS02); oxidisers (GHS03); gases under pressure (GHS04); corrosives (GHS05); acute toxicity — severe (GHS06); irritants and lower-severity acute toxicity (GHS07); serious health hazards including carcinogens and reproductive toxicants (GHS08); and environmental hazards (GHS09). A substance may carry more than one pictogram. The CLP Regulation's Annex I determines which pictogram applies to each classification.

What is the difference between a CLP chemical pictogram and a workplace safety signboard? A CLP pictogram is a red-bordered diamond that appears on a container or pipe label to communicate the intrinsic chemical hazard of a substance. A workplace safety signboard is a wall- or post-mounted sign (triangular, round, or rectangular depending on category) that communicates a hazard present in an area or associated with equipment. They are governed by different legal instruments and serve different functions — though both may be required for the same substance.

What do signal words 'Danger' and 'Warning' mean on a chemical label? Both are CLP signal words that indicate severity. 'Danger' denotes more severe hazard categories; 'Warning' denotes less severe ones. Where a substance's classifications would trigger both, only 'Danger' appears — 'Warning' is omitted. Signal words do not appear on workplace safety signboards.

What happened to the old orange-square hazard symbols? The orange-square symbols that preceded the current system have been replaced by the GHS-aligned CLP format — black symbol inside a red diamond on a white background. Orange-square labelling does not meet the requirements of the retained CLP Regulation and should be treated as non-compliant. Employers should audit their workplace for any containers still carrying pre-CLP labelling.

What does the health hazard / serious health hazard symbol (GHS08) mean? GHS08 — the human silhouette with a starburst — covers hazard classes including respiratory sensitisation, carcinogenicity, reproductive toxicity, specific target organ toxicity from repeated exposure, aspiration hazard, and germ cell mutagenicity. These are effects that may not be immediately apparent but manifest over time or through specific exposure routes. No direct equivalent workplace warning signboard exists in Schedule 1 of the Safety Signs and Signals Regulations 1996; where this pictogram must appear at a storage room entrance, the CLP pictogram itself is used.

What does the corrosive symbol (GHS05) mean and where must it appear? GHS05 — showing liquid attacking a surface and a hand — indicates substances corrosive to metals, causing skin corrosion, or causing serious eye damage. It must appear on the container label for any substance classified in those categories. Where the substance is stored in significant quantities, the workplace warning sign 'Corrosive material' (triangular, yellow) should mark the storage area entrance, as it is one of the named equivalent signs in Schedule 1, regulation 3.2 of the Safety Signs and Signals Regulations 1996.

Can I use the 'General danger' sign for a chemical storage room? Only if the room contains a number of different hazardous substances or mixtures. The 'General danger' warning sign must not be used to warn about a specific hazardous substance or mixture. For a room storing a single substance, you must use the substance-specific warning signboard or, where none exists, the relevant CLP pictogram. (Health and Safety (Safety Signs and Signals) Regulations 1996, regulation 2 — Conditions of use)

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Disclaimer: This page is for general guidance only. All information must be reviewed and adapted to your specific site, task, and contractor circumstances by a competent person before use. Nothing in this page constitutes legal advice or guarantees compliance with any regulatory requirement. Regulatory text should always be consulted in its current form via legislation.gov.uk.