Chemical warning signs are safety symbols found on containers, especially those used in the laboratory. The symbols are also found on tanks or containers that are used to carry, store or transport certain chemicals. Containers holding flammable fuels such diesel, petrol and natural gas, as well as those containing toxic chemicals normally bear warning symbols. These symbols indicate the danger (hazard) likely to be caused by the chemicals they contain if carelessly handled.



When performing experiments in the laboratory it is important to read the safety signs on chemical containers. This will minimize the chances of causing accidents in the laboratory.


The Basic Chemical Warning Signs


The Concept of Warning Signs
Before conducting any experiment in the laboratory you must be aware whether the chemical you want to use is toxic, corrosive, flammable, oxidant, explosive or harmful. This information will help you know how to handle the chemicals safely. 

Proper handling of chemicals enables you avoid unnecessary accidents. Below is an explanation pertaining to some hazard labels represented by the symbols above.

Toxic

Toxic substances include those that can poison you or the other person working close to you in the laboratory. These substances can kill within a short time or after some few days. They should not be allowed to get into your body through body orifices (month, nose, eyes, ears, etc). 

Neither should they be allowed to contact your skin. They become even more dangerous when they get into the body. If it happens that these substances touch your skin accidentally, wash it immediately with ample water.

Corrosive

Corrosive substances refer to those chemicals that can burn or corrode (eat away) your skin. They can also corrode wood or metals. One can become blind if such substances accidentally get into his/her eyes. If they contact your skin, wash it immediately with a lot of water. 

Examples of corrosive substances commonly found in a school laboratory are concentrated mineral acids such as sulphuric acid, hydrochloric acid and nitric acid, and concentrated alkalis such as sodium hydroxide, potassium hydroxide and ammonia.

Flammable

These chemicals catch fire easily. For this case, they should be kept away from flames or fires. They can be set into fire by any kind of sparks, be it from welding or fire. When working with flammable chemicals in the laboratory all burners must be put off. 

These chemicals are usually very volatile. The containers used to carry them must be stoppered immediately after every use. Examples of flammable chemicals are methylated spirit, ether, acetone and methanol.

Explosive

Explosive chemicals are those that explode rapidly upon detonation (set into fire or ignited). Because the reaction is rapid, it results into throwing off particles at a high speed. For this reason, they should not be kept in glass containers. 

This is because during explosion the particles will disperse around and cause serious injuries to people. Those explosive chemicals that can react without external detonation are even more dangerous

Oxidizing agents

These chemicals can stimulate a burning substance to burn efficiently and faster. Therefore, they must be kept away from fires no matter how small that fire may be. An example of oxidizing agent is oxygen gas.

Harmful or irritant

Harmful substances are those that can impair your health or make you fall sick. They do not normally kill instantly but have detrimental effects following a long exposure to them. These chemicals do not kill immediately. However, care must be taken when handling or dealing with them. 

Irritating substances cause pains when in contact with the body. They are dangerous to health when in contact with the body surface for a long period of time.