The Definitive Guide to the GHS Hazard Classification System and How to Enhance Lab Safety in Two Easy Steps

Since there are many more potential hazards and risks associated with laboratory work than the average workplace, it is important to understand them all and review safety practices regularly, so you can focus on the important work that you are doing. 

GHS Hazard Classification System stands for the Globally Harmonized System of Classification and Labelling of Chemicals. 

GHS Hazard Classification System defines and classifies the hazards of chemical products.

Hazard vs Risk

A hazard is the intrinsic harm (physical injury/damage to health, property, and/or the environment) that something can cause. It is directly related to the unique physical and chemical properties of a material (e.g. capacity to burn, explode, corrode, etc.).

A risk however is not intrinsic. It is the likelihood or chance of harm occurring, modulated through lab safety protocols. You may remember learning about lab safety in high school chemistry class or first year University? In those early days we may have just gone through the motions, but over the years of continual lab safety training and maturation, minimizing risk through knowing your reagents, awareness of your surrounds, and optimizing space and use of equipment becomes ‘second nature’.  

An international team of hazard communication experts developed GHS Hazard Classification System.

Minimizing laboratory risks is a two-step process

Step 1: Understand the hazards associated with all the reagents you are working with and how they are classified.

How are chemical hazards classified?

Chemical hazards are now classified and communicated according to the Globally Harmonized System of Classification and Labeling of Chemicals (GHS), an internationally agreed-upon system first established in 1992 by the United Nations and fully implemented by employers, distributers, chemical manufacturers, and importers in 2015. Prior to this system, countries were using their own labeling system, prone to: (i) individuals not recognizing the hazards of their packages due to language barriers, and (ii) inconsistent shipping costs.

In addition to standardizing the format and contents of chemical labels, the GHS Hazard Classification System entails: global standardized criteria for hazard classification, universal warning pictograms to facilitate easy physical, health and/or environmental hazard recognition, and safety data sheets (SDS).

(i) Standardized hazard labels present on all barrels, boxes, drums, bottles, buckets, canisters include:

  • Product identifiers (Name, CAS number, etc.)
  • One or more GHS pictograms that convey basic hazard information
  • One of two signal words used to emphasize the relative level of severity (danger or warning)
  • Hazard statements (standard phrases that describe the nature of the hazard)
  • Precautionary statements (measures to minimize or prevent adverse effects)
  • Supplier information (company name, address, phone number)

(ii) GHS pictograms are a standardized set of nine symbols used to quickly convey a chemical’s unique health, physical, and environmental hazard information.[1]For chemicals that are represented by more than one pictogram, the most significant one is listed first.

(iii) Safety data sheets provided by chemical manufacturers or suppliers contain more detailed information than what is on a label:

  1. Identification of the substance/mixture and of the company/undertaking
  2. Hazard(s) identification (including pictograms, signal words, hazard statements, and precautionary statements)
  3. Composition/information on ingredients
  4. First aid measures
  5. Firefighting measures
  6. Accidental release measures
  7. Handling and storage
  8. Exposure controls/personal protection
  9. Physical and chemical properties
  10. Stability and reactivity
  11. Toxicological information
  12. Ecological information
  13. Disposal considerations
  14. Transport information
  15. Regulatory information
  16. Other information

Note that some countries may still use material safety data sheet (MSDS) under the old OSHA HazCom system.

Three overarching types of hazards and 30 hazard classes

The GHS classification of hazardous chemicals is divided into three overarching types of hazards, which are further divided into class and category to describe the nature and degree of hazard (if applicable) respectively.  The lower the category, the more dangerous the hazard.

Health hazards

Physical hazards

 Environmental Hazards

Ten health hazard classes that pose a threat to human health:

Eighteen physical hazard classes that pose a threat to physical injury or damage to property:

Two hazard classes that pose a threat to the environment:

+ 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)

+ Specific target organ

toxicity (repeated exposure)

+ Aspiration toxicity

+ Explosives

+ Flammable gases

+ Flammable liquids  

+ Pyrophoric liquids

+ Flammable solids

+ Pyrophoric solids

+ Aerosols

+ Chemicals under pressure

+ Gases under pressure

+ Self-reactive substances and mixtures

+ Self-heating substances and mixtures

+ Substances and mixtures that emit flammable gases upon contact with water

+ Oxidizing gases

+ Oxidizing liquids

+ Oxidizing solids

+ Organic peroxides

+ Corrosive to metals

+ Desensitized explosives

+ Aquatic toxicity (acute or chronic)

+ Hazardous to the ozone layer


More information about GHS

Refer to the (8th) revised 2019 copy of the GHS “Purple Book” for more detailed information. Even though it is over 500 pages, the table of contents can help you to locate the information you are in search of.

Step 2: Modulate your lab set-up and related activities to decrease the likelihood of harm occurring.

1. Before an experiment:
    • Get acquainted with your procedure and fully review SDS information for each of your reagents to account for associated hazards and first aid measures.
    • Determine appropriate PPE (Section 8: exposure controls/personal protection).
    • Walk through emergency protocols: know where fire extinguishers, spill kits, and first aid kits are located. Ensure a clear path to emergency exits.
    2. During an experiment:
      • Protect yourself by maintaining appropriate PPE.
      • Clean as you go (if possible). This will prevent confusion from excess glassware and decrease the risk of spills.
      • Only dispense what you need.
      • Keep incompatible material away from each other.
      3. After an experiment:
        • Segregate waste and store in appropriate containers.

        Reflect on your work: consider the risks encountered and how to reduce those risks in the future.



        1. Hazard Communication Standard Pictogram
        By Qinling Li


        Just added to your wishlist:
        My Wishlist
        You've just added this product to the cart:
        Go to cart page