GHS Classification, Labels and Safety Data Sheets

Why This Topic Matters

Hazard Communication is consistently one of the most frequently cited OSHA standards every year, and it touches virtually every workplace that uses chemicals. For the BCSP Associate Safety Professional (ASP) exam, the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) sits inside the Safety Programs and Concepts domain, but it also connects to industrial hygiene, emergency response, fire protection, and risk assessment. Questions on this topic tend to be knowledge-based and highly testable: the standard contains fixed numbers, fixed lists, and fixed sequences that lend themselves to multiple-choice items. A candidate who knows the six label elements, the nine pictograms, the sixteen SDS sections in order, and the logic of hazard categories can reliably collect points here. Beyond the exam, a safety professional who cannot interpret a label or an SDS cannot perform a chemical risk assessment, select PPE, or build a compliant written HazCom program.

What GHS Is

GHS is an internationally agreed framework developed by the United Nations and published in the so-called Purple Book. Its goal is to make chemical hazard information consistent across borders so that a label or data sheet from one country communicates the same message in another. GHS standardizes three things:

1. Classification criteria for physical, health, and environmental hazards.
2. Label elements including pictograms, signal words, hazard statements, and precautionary statements.
3. Safety Data Sheet (SDS) format with a fixed 16-section structure.

In the United States, OSHA incorporated GHS into the Hazard Communication Standard (HCS), 29 CFR 1910.1200, in 2012 (often called HazCom 2012), aligning primarily with GHS Revision 3. OSHA published an updated final rule in 2024 aligning mostly with GHS Revision 7, with phased compliance dates. GHS is a building block approach: each country adopts the pieces it chooses. OSHA did not adopt the environmental hazard classes, so the environment pictogram is non-mandatory under OSHA, although EPA, DOT, and international shipments may still use it.

A key vocabulary point: GHS replaced the term Material Safety Data Sheet (MSDS) with Safety Data Sheet (SDS), and the standard now uses the term hazard classification rather than hazard determination.

How It Works: Classification

Classification is the responsibility of the chemical manufacturer or importer (distributors may rely on their classifications, and employers may rely on them as well unless they choose to reclassify). Classification has two levels:

Hazard class describes the nature of the hazard (for example, flammable liquid, acute toxicity, carcinogenicity).
Hazard category describes the severity within that class. Categories are numbered, and Category 1 is always the most severe; higher numbers mean lower severity. Some classes use letters (for example, Carcinogen 1A, 1B, 2) or types (Organic Peroxide Types A through G, Self-Reactive Types A through G).

Physical hazard classes (16 under GHS; OSHA adopted them, and the 2024 update added desensitized explosives and refined others): explosives, flammable gases, aerosols, oxidizing gases, gases under pressure, flammable liquids, flammable solids, self-reactive substances, pyrophoric liquids, pyrophoric solids, self-heating substances, substances that emit flammable gases in contact with water, oxidizing liquids, oxidizing solids, organic peroxides, and corrosive to metals. OSHA also recognizes combustible dust, pyrophoric gases, and simple asphyxiants as hazards covered by the standard even though they are not classic GHS classes.

Health hazard classes (10): acute toxicity, skin corrosion/irritation, serious eye damage/eye irritation, respiratory or skin sensitization, germ cell mutagenicity, carcinogenicity, reproductive toxicity, specific target organ toxicity single exposure (STOT-SE), specific target organ toxicity repeated exposure (STOT-RE), and aspiration hazard.

Environmental hazard classes (not adopted by OSHA): hazardous to the aquatic environment (acute and chronic) and hazardous to the ozone layer.

Classification criteria you should memorize

Flammable liquids (flash point and boiling point based):
Category 1: flash point below 23 degrees C (73.4 F) and initial boiling point at or below 35 C (95 F).
Category 2: flash point below 23 C and initial boiling point above 35 C.
Category 3: flash point at or above 23 C and at or below 60 C (140 F).
Category 4: flash point above 60 C and at or below 93 C (199.4 F).
Note that the GHS category 4 flammable liquid corresponds roughly to what older OSHA language called a combustible liquid; GHS eliminated the separate combustible liquid term.

Acute toxicity (oral LD50, mg/kg body weight):
Category 1: 5 or less.
Category 2: greater than 5 up to 50.
Category 3: greater than 50 up to 300.
Category 4: greater than 300 up to 2000.
Category 5 (greater than 2000 up to 5000) exists in GHS but was not adopted by OSHA. Categories 1 through 3 carry the skull and crossbones pictogram and the signal word Danger; Category 4 carries the exclamation mark and Warning.

Mixtures are classified using test data on the mixture itself if available, bridging principles if similar mixtures were tested, or by calculation and cut-off values based on ingredients. Common cut-offs are 1 percent for most health hazards and 0.1 percent for carcinogens, mutagens, reproductive toxins, and respiratory sensitizers.

How It Works: Labels

Labels on shipped containers must contain six elements:

1. Product identifier that matches the SDS.
2. Signal word: either Danger (more severe) or Warning (less severe). Only one signal word appears per label; if both would apply, Danger takes precedence. Some low-severity categories have no signal word.
3. Hazard statement(s): standardized phrases describing the nature and degree of hazard, coded H2xx for physical hazards, H3xx for health hazards, and H4xx for environmental hazards (for example, H225 Highly flammable liquid and vapour). The codes themselves are not required on the label, only the text.
4. Pictogram(s): black symbol on white background inside a red diamond (square set on point) border. On shipped labels the border must be red; OSHA does not permit black borders on shipped containers in the U.S.
5. Precautionary statement(s): standardized phrases in four types: Prevention (P2xx), Response (P3xx), Storage (P4xx), and Disposal (P5xx). General statements are P1xx.
6. Name, address, and telephone number of the manufacturer, importer, or other responsible party.

The nine GHS pictograms and what they represent:

Health Hazard (silhouette with starburst on chest): carcinogen, mutagen, reproductive toxicity, respiratory sensitizer, target organ toxicity, aspiration hazard.
Flame: flammables, pyrophorics, self-heating, emits flammable gas, self-reactives, organic peroxides.
Exclamation Mark: irritant (skin and eye), skin sensitizer, acute toxicity Category 4 (harmful), narcotic effects, respiratory tract irritation, hazardous to ozone layer (non-mandatory).
Gas Cylinder: gases under pressure (compressed, liquefied, refrigerated liquefied, dissolved).
Corrosion (test tubes dripping on hand and metal bar): skin corrosion, serious eye damage, corrosive to metals.
Exploding Bomb: explosives, self-reactives, organic peroxides.
Flame Over Circle: oxidizers (gases, liquids, solids).
Skull and Crossbones: acute toxicity Categories 1, 2, and 3 (fatal or toxic).
Environment (dead fish and tree): aquatic toxicity. Non-mandatory under OSHA.

Note the overlaps: self-reactives and organic peroxides can carry both the flame and exploding bomb; the exclamation mark is not used when the skull and crossbones appears for the same hazard, and it is not used for skin or eye irritation when the corrosion pictogram already appears.

Workplace labels give employers flexibility. Employers may use the shipped label as-is, or use an alternative system (such as NFPA 704 or HMIS) on in-plant containers, as long as the system conveys the product identifier and general hazard information and employees are trained to understand it. Portable containers intended for immediate use by the employee who filled them do not require labels. Employers must not remove or deface shipped labels, and labels must be legible, in English (other languages may be added), and prominently displayed.

A critical exam distinction: NFPA 704 and HMIS number hazards in the opposite direction from GHS. In NFPA 704, 4 is the most severe and 0 is the least; in GHS, Category 1 is most severe. Workers must be trained on this difference when both systems are used in the same facility.

How It Works: Safety Data Sheets

The SDS must follow a fixed 16-section format in this exact order:

1. Identification: product identifier, manufacturer contact, emergency phone number, recommended use and restrictions.
2. Hazard(s) identification: classification, label elements (signal word, pictograms, statements), hazards not otherwise classified.
3. Composition/information on ingredients: chemical name, CAS number, concentration or ranges, trade secret claims.
4. First-aid measures: by route of exposure, symptoms, need for immediate medical attention.
5. Fire-fighting measures: suitable extinguishing media, specific hazards, protective equipment for firefighters.
6. Accidental release measures: personal precautions, containment and cleanup.
7. Handling and storage: safe handling practices, storage conditions, incompatibilities.
8. Exposure controls/personal protection: OSHA PELs, ACGIH TLVs, other exposure limits, engineering controls, PPE.
9. Physical and chemical properties: appearance, odor, pH, flash point, boiling point, vapor pressure, vapor density, specific gravity, solubility, LEL and UEL, autoignition temperature, and more.
10. Stability and reactivity: reactivity, chemical stability, hazardous reactions, conditions to avoid, incompatible materials, hazardous decomposition products.
11. Toxicological information: routes of exposure, symptoms, acute and chronic effects, LD50 and LC50 values, carcinogen listings (NTP, IARC, OSHA).
12. Ecological information (non-mandatory for OSHA).
13. Disposal considerations (non-mandatory for OSHA).
14. Transport information (non-mandatory for OSHA).
15. Regulatory information (non-mandatory for OSHA).
16. Other information: date of preparation or last revision.

Sections 12 through 15 are non-mandatory because they fall under other agencies (EPA and DOT), but the headings must still appear so the format stays consistent. SDSs must be readily accessible to employees during each work shift in their work area; electronic access is acceptable if there is no barrier to immediate access and a backup exists for power or system failures. Manufacturers must provide an SDS with the first shipment and whenever the SDS is updated. New hazard information must be incorporated into the SDS and label within three months (and the 2024 rule maintains six months for labels on shipped containers in some cases, so know the current rule you are tested on).

Employer Program Requirements

Every employer with hazardous chemicals must maintain a written hazard communication program that describes how labeling, SDSs, and training are handled, includes a chemical inventory (list of hazardous chemicals by product identifier), and explains how hazards of non-routine tasks and chemicals in unlabeled pipes are communicated. The program must address multi-employer worksites so contractors receive hazard information. Training must be provided at initial assignment and whenever a new hazard is introduced, and must cover how to read labels and SDSs, methods to detect releases, physical and health hazards, protective measures, and the details of the written program. Training must be effective, meaning in a language and manner workers understand.

Trade secrets: a manufacturer may withhold the specific chemical identity or exact concentration if it is a legitimate trade secret, but the SDS must still disclose hazard properties and the identity must be released to health professionals in a medical emergency immediately, and in non-emergencies upon written request with a confidentiality agreement.

Exemptions: HazCom does not cover hazardous waste regulated under RCRA, tobacco products, wood and wood products (unless treated or to be sawed, creating dust), articles, food and alcoholic beverages for consumption, drugs in final form for personal consumption, consumer products used in the same manner and frequency as a consumer, and certain other categories. Laboratories and sealed-container warehousing operations have reduced requirements.

Exam Tips: Answering Questions on GHS Classification, Labels and Safety Data Sheets

Tip 1: Memorize fixed lists and sequences. The exam loves to ask what is in a specific SDS section or which element is not a required label element. Use a mnemonic for the first eight SDS sections, which are the most tested: Identification, Hazards, Composition, First aid, Fire, Accidental release, Handling, Exposure. Know that physical properties are Section 9, stability and reactivity is Section 10, and toxicology is Section 11.

Tip 2: Remember that lower category number means higher severity. If a question describes a chemical in Category 1 versus Category 4, Category 1 is the more hazardous. Then recall that NFPA 704 and HMIS run the opposite way. A question that asks about worker confusion between systems is pointing at this reversal.

Tip 3: Know who is responsible for what. Manufacturers and importers classify, label shipped containers, and prepare SDSs. Distributors pass along labels and SDSs. Employers maintain the written program, ensure workplace labeling, keep SDSs accessible, and train. If a question asks who must classify a chemical, the answer is the manufacturer or importer, not the employer.

Tip 4: Match pictograms to hazards precisely. Distractors often swap the exclamation mark and the skull and crossbones (acute toxicity Category 4 versus Categories 1 through 3) or swap the health hazard pictogram and the exclamation mark (chronic serious effects such as carcinogenicity versus irritation). Flame over circle is oxidizers only; gas cylinder is gases under pressure only. The environment pictogram is the one OSHA does not require.

Tip 5: Only two signal words exist. If an answer choice offers Caution, Hazard, or Notice as a GHS signal word, eliminate it. Danger is more severe than Warning, and only one appears on a label.

Tip 6: Know the code families. H2 physical, H3 health, H4 environmental. P1 general, P2 prevention, P3 response, P4 storage, P5 disposal. A question showing H350 (May cause cancer) is a health hazard; P280 (Wear protective gloves) is a prevention statement.

Tip 7: Know the numbers that recur. Flammable liquid flash point cut-offs of 23 C, 60 C, and 93 C; oral LD50 cut-offs of 5, 50, 300, and 2000 mg/kg; mixture cut-offs of 1 percent and 0.1 percent; sixteen SDS sections; nine pictograms with eight mandatory; six label elements; two signal words; three months to update after new hazard information.

Tip 8: Read for OSHA versus pure GHS. The ASP is a U.S.-based exam. If a question references OSHA or the HCS, apply OSHA adoptions: no environmental classes, no acute toxicity Category 5, no flammable liquid in extended categories, red borders required on shipped labels, Sections 12 through 15 non-mandatory. If the question says simply GHS or the UN Purple Book, the broader system applies.

Tip 9: Watch for the word shipped. Full six-element labels are required on shipped containers. Workplace containers may use alternative systems if employees are trained. Portable containers for immediate use by the person who filled them need no label. Many questions hinge on this word.

Tip 10: Apply the SDS to scenarios. Scenario questions ask where to find information to solve a problem: a spill points to Section 6, a fire to Section 5, PPE selection to Section 8, an exposure limit to Section 8, a flash point or vapor density to Section 9, an incompatibility to Section 10 (also Section 7), and a first-aid response to Section 4. Practice mapping the problem to the section number quickly.

Tip 11: Eliminate outdated terminology. MSDS, hazard determination, and combustible liquid are pre-2012 terms. If an answer choice uses modern GHS language (SDS, hazard classification, flammable liquid Category 4), it is more likely correct in a question about current requirements.

Tip 12: Think like a safety professional, not just a test taker. When two answers seem plausible, choose the one that reflects the hierarchy of the standard: hazard information must flow from manufacturer to employer to worker without loss, and the worker must be able to understand it. Any answer that would obscure, remove, or delay hazard information is wrong.

Summary

GHS harmonizes how chemical hazards are classified, labeled, and documented. Under OSHA 29 CFR 1910.1200, manufacturers and importers classify chemicals into hazard classes and numbered categories (1 being most severe), produce shipped labels with six required elements and red-bordered pictograms, and prepare 16-section SDSs. Employers build a written program, ensure labels and SDSs are present and accessible, and train workers. Master the fixed lists, the direction of severity numbering, the OSHA-specific building block choices, and the responsibility chain, and you will handle every GHS question the ASP exam presents.