General Advice on

Handling Hazardous Substances

General Rules for Handling Hazardous Substances
List of Hazard Symbols

1. General Rules for Handling Hazardous Substances

The classroom experiments are designed to enable students to gain a theoretical understanding of chemical processes and get a feel for how the substances should be handled. The basic rule is that all chemicals, reagents and dye solutions must be handled with care and caution. It goes without saying that students and teachers must not be exposed to any unnecessary health hazards during the experiments.

Experiments must also convey an understanding of the potential dangers as well as the handling of hazardous substances. For example, it should be made clear to students that their handling of petrol or drain cleaners at home should reflect their handling of solvents or sodium hydroxide in the classroom.

When handling hazardous substances, the instructions contained in the most up-to-date versions of the safety data sheets for the individual substances (according to EC Directive 91/155/EEC) must be followed and the relevant accident prevention regulations (e.g. GUV 19.16) observed.

Some of the most important general rules of conduct are listed below, though it should be noted that this is not an exhaustive list:

  • Eating, drinking and smoking are not permitted in the experiment labs.
  • Always wear protective goggles during experiments.
  • It is essential to ensure that hazardous substances do not come into contact with the skin, eyes and mucous membranes; if required, suitable personal protective clothing (gloves, protective goggles) should be worn.
  • Experiments which can lead to the generation of harmful fumes or gases must be conducted in a fume cupboard.
  • Any splashes of chemicals on the skin should be rinsed off immediately, using the liquids specified for the particular hazardous substances; never use organic solvents for this because of the risk of absorption.
  • If chemicals come into contact with the eyes, rinse thoroughly with a gentle jet of water; open the eyelids wide and move the eyes in all directions; seek medical help from an eye specialist immediately.
  • Any clothes that have absorbed chemicals should be removed immediately.
  • Lab coats must be made of cotton.
  • In the event of an accident or someone taking ill, always seek medical advice, informing the doctor of the cause of the accident, including a full description of the chemicals.
  • Experiments involving a vacuum or compressed gases should only be carried out after thorough instruction and double-checking the apparatus (risk of implosion / explosion).
  • Hoses must be secured to ensure that they do not slip off, e.g. by using hose clips.
  • Ensure protection against accidental contact if there is high voltage and mains power.
  • The R and S phrases that apply to the chemicals being used must be kept up to date and observed at all times. They can be obtained from the chemical suppliers.
  • Teacher experiments involving the risk of explosion or spray must always be conducted behind safety screens or in a sealed fume cupboard.
  • When handling flammable solvents and reagents, all ignition sources must be extinguished.
  • All containers containing chemicals, reagents or dye solutions must be resealed immediately after use and should, if possible, be returned to their storage location immediately.
  • Funnels must be used when pouring hazardous substances into narrow-necked vessels, and attention paid to ensure that the air can escape unhindered while the substance is being poured. When decanting liquids from storage vessels into experiment apparatus, it generally makes sense to pour the required quantity into a suitable clean beaker first and then into the apparatus, for example when pouring small quantities of concentrated sulphuric acid from a 1-litre flask into test tubes.
  • Mouth pipetting is strictly prohibited. Mechanical devices must always be used for pipetting.
  • The chemicals used in the experiments must be disposed of in accordance with recognised methods. The local education authority's regulations governing the proper disposal of chemicals must be observed.

2. Hazard Symbols and their Meaning

The following list provides an overview of the statutory symbols as used for the designation of hazardous substances in this publication along with the description and meaning of each hazard:

international dangerous goods symbolE: Explosive
Classification: substances and preparations which may also react exothermically without atmospheric oxygen and which under defined test conditions detonate, quickly deflagrate or upon heating explode when partially confined.
Caution: avoid shocks, jolts, friction, sparks, fire and heat.

international dangerous goods symbolO: Oxidising
Classification: organic peroxides which are flammable even when not in contact with other flammable material. Other substances and preparations which as a rule are not flammable themselves but which significantly increase the risk of fire and the severity of a fire upon contact with flammable material, primarily through the release of oxygen.
Caution: keep away from flammable material.
Ignition hazard: fires that have broken out can be made worse and more difficult to put out.

international dangerous goods symbolF: Highly Flammable
Classification: liquids with a flash point below 21°C but which are not extremely flammable. Solid substances and preparations which may readily catch fire after brief contact with a source of ignition and which continue to burn or to be consumed after removal of the source of ignition.
Caution: keep away from naked flames, sparks and heat sources.

international dangerous goods symbolF+: Extremely Flammable
Classification: liquids with a flash point below 0°C and a maximum boiling point of 35°C. Gases and gas mixtures which are flammable in contact with air at ambient temperature and pressure.
Caution: keep away from naked flames, sparks and heat sources.

international dangerous goods symbolT: Toxic
Classification: Substances or preparations which in very low quantities cause death or acute or chronic damage to health when inhaled, swallowed or absorbed via the skin. This may lead to severe and possibly irreversible damage to health from immediate, prolonged or repeated exposure, particularly in the case of carcinogenic or mutagenic effects or effects that are toxic for reproduction.
Caution: any contact with the human body must be avoided. If someone takes ill, seek medical advice immediately. In the case of substances that are classified as carcinogenic, mutagenic or toxic for reproduction, this danger is made explicit. Special regulations must be observed when handling these substances!

international dangerous goods symbolT+: Very Toxic
Classification: Substances or preparations which in very low quantities cause death or acute or chronic damage to health when inhaled, swallowed or absorbed via the skin. This may lead to severe and possibly irreversible damage to health from immediate, prolonged or repeated exposure.
Caution: any contact with the human body must be avoided. If someone takes ill, seek medical help immediately.

international dangerous goods symbolC: Corrosive
Classification: a substance is considered to be corrosive if, when it is applied to healthy intact skin, it produces full thickness destruction of skin tissue, or if this result can be predicted.
Caution: avoid contact with the eyes, skin and clothes by taking special protective measures. Do not inhale fumes! In the event of an accident or someone taking ill, seek medical help immediately!

international dangerous goods symbolXn: Harmful
Classification: Substances or preparations which may cause acute or chronic damage to health when inhaled, swallowed or absorbed via the skin. This may lead to severe and possibly irreversible damage to health from immediate, prolonged or repeated exposure, in particular where there is suspicion of carcinogenic, or mutagenic effects or effects that are toxic for reproduction. May cause sensitisation by inhalation (if classified as R42).
Caution: contact with the human body must be avoided. If substances are suspected of being carcinogenic, mutagenic or toxic for reproduction, this fact is made explicit.

international dangerous goods symbolXi: Irritant
Classification: Non-corrosive substances which, through immediate, prolonged or repeated contact with the skin or mucous membranes, may cause inflammation. May cause sensitisation by skin contact (if classified as R43).
Caution: Avoid contact with the eyes and skin, do not inhale fumes.

international dangerous goods symbolN: Dangerous for the Environment
Classification: Substances and preparations which, were they to enter the aquatic or non-aquatic environment, may cause immediate or delayed environmental damage by altering the ecological balance. Some substances or their breakdown products can impact negatively on different components of an ecosystem at the same time.
Caution: in accordance with the hazard potential, the substance must not be emptied into drains or allowed to pollute the soil or the environment. Observe special disposal regulations!