A quick guide to lab safety

A quick guide to lab safety

Table of contents

  • Introduction to Lab safety symbols and their meanings
  • Explosive
  • Oxidising
  • Extremely Flammable
  • Corrosive
  • Dangerous for Environment
  • Harmful
  • Highly Flammable
  • Toxic
  • Irritant
  • Very Toxic

  • Introduction to Lab safety symbols and their meanings

    Enter a lab and you will be greeted with a number of signs of various dimensions pasted across the doors and hallways. Some of the symbols on these signs are very much familiar in our day to day life as we often encounter them in places other than labs as well. However, most of the symbols correspond to the specific environment they are found in. Some are self-explanatory, and some need a bit of head-scratching to know their true purpose. This article will help you understand the various symbols found in labs and we will explore their true purpose, which should be taken seriously according to their hierarchy and categorisation:


    This sign is usually displayed when the substance under study is explosive. It should be kept away from open flame and anything that could start the ignition including electricity sparks and cigarettes. Usually, these substances are kept under surveillance and are issued through a proper check and balance to control their circulation. The amount usually sanctioned for the student’s use is small mainly to prevent dangerous consequences. Examples include Acetylides of heavy metal, aluminium-containing polymeric propellant, Aluminum ophorite explosive and Amatex.


      Any substance, mostly oxides, that under normal conditions release oxygen and when coming in contact with a combustible substance explode or promote existing combustion reaction. Some of the examples of such compounds include Ammonium perchlorate, Bromine, Chromic acid, Dibenzoyl peroxide.

      Extremely flammable

      The compounds, as the name suggests, have a natural tendency to become inflamed at extremely low temperatures less than 0°C and a boiling point (or, in the case of a boiling range, the initial boiling point) less than or equal to 35°C. To minimise inadvertent burning, they are stored in sealed containers away from direct contact with heat and sparks. Typically, fires generated by very flammable chemicals are also difficult to extinguish. Diethyl ether, hydrogen, and acetylene are some examples of very flammable chemicals. It should be noted that some oxidising agents may also be extremely flammable substances.


      Corrosive substances are laboratory chemicals that are usually acids and bases with extreme pH value and burn the skin when coming in contact with it. They are usually stored in airtight brown containers/bottles with labels and warnings. Usually, gloves are used when handling the substance, however, some corrosive agents may pose an added danger with specific types of gloves. Some examples of corrosive agents are HCL, Sulphuric Acid, and Sodium Hydroxide. 

      Dangerous for Environment 

      Compounds or rays that, when released into water or soil, represent a threat to the environment, either in their pure form or in combination with other man-made or natural compounds. These substances are often the byproducts of a chemical or physical process or gases that have escaped from a confined environment. Biological samples, such as bacteria, viruses, or animals, may be found in ecologically hazardous chemicals. Cosmic rays, X-rays, biological substances, effluents, industrial chemicals, bleaches, and other compounds that are hazardous to the environment are examples.


      This is a broad categorisation and includes anything and everything that has a tendency to pose bodily harm to the person in contact. These may include acids, biological compounds, physical sharp objects and even machines and electricity. 

      Highly flammable

      Highly inflammable compounds are not very much different from extremely flammable compounds as both have a tendency to catch fire under altered circumstances. However, highly flammable compounds have a slightly higher burning point. The examples include viscous compounds such as diesel, petrol and acetone


      Toxic compounds are any compounds, natural or synthetic, fumes, volatile, solid which once inhaled and taken into the body causes irreversible damage to the body or even death. These compounds are also highly regulated in the labs to prevent accidental swallowing. This is the very reason eating is not allowed in any lab. Some of the toxic compounds are mercury, KCN, NaCN, rat poison, and nerve gas. 


      Irritants are substances that, when in contact with the body or any of its organs, produce discomfort and irritation. These might be in the form of liquids or gases. Because of their capacity to reach the respiratory system and the eyes, gaseous irritants are usually more hazardous than liquid irritants. Some examples are bromine fumes, nitric acid fumes, and chlorine gas.

      Very toxic 

      Very toxic chemicals are a subset of toxic compounds with a high level of toxicity. Even in trace concentrations, very poisonous chemicals are dangerous. Mercury compounds, potassium and sodium cyanide, and ethidium bromide are a few examples.