Classes of Chemicals

Class Label Description Examples
1 explosives substance or article that has a mass explosion risk. gunpowder, fireworks, fuses detonators
2 gases compressed, liquefied or dissolved under pressure. Liquid nitrogen, carbon dioxide, oxygen, LPG
3 flammable liquids liquids which ignite on contact with a source of ignition. ether, acetone, petrol, butane
4 flammable solids substances easily ignited or liable to spontaneous combustion, substances which on contact with water emit flammable gases. sulphur, picric acid, carbon, phosphorous, nitrocellulose
5 oxidising agents oxidising agents, organic peroxides. calcium hypochlorite, hydrogen peroxide, benzoyl peroxides
6 poisonous substances substances which are liable to cause death or serious injury to humans if swallowed, inhaled or by skin contact. pesticides, bacterial cultures, calcium cyanide, lead arsenate.
7 radioactive substances materials which spontaneously emit radiation. uranium, isotopes
8 corrosives solids or liquids able to damage living tissue. sulphuric acid, nitric acid, sodium hydroxide
9 miscellaneous dangerous goods. dry ice, fishmeal, maritime hazards

All chemical containers must be clearly marked with the name of the contents and a label indicating its class. Chemicals must be stored by hazard category in accordance with the Dangerous Goods Act 1986 and not simply alphabetically. Information regarding labelling and storage of chemicals can be obtained from the Safety Officer.

Dangerous Chemicals & Hazards

STRONG ACIDS – Always add ACID TO WATER when diluting strong acids.

MINERAL ACIDS – will burn the skin. Chromic acid being specially corrosive.

STRONG ALKALIS – Sodium, potassium or calcium hydroxide, and ammonia in solution or undiluted, all rapidly affect the skin and cause painful burns. The effect of strong alkalis on the eyes is immediate and disastrous (see First Aid; page 12, Chemicals splashed in the eye).

When opening a new bottle of ammoniathere is invariably a slight spray. The procedure should be carried out in a fume cupboard with the glass front lowered to protect the eyes.

METALS – Mercury vapour is a cumulative poison. Any spillage of mercury should be cleared up immediately. A vacuum pump with a trap may be used to recover spilt mercury


Dermatitis – The skin can be damaged by many chemicals. Most organic solvents dissolve the protective secretions of the skin and dermatitis, allergic reaction or even cancer can result after prolonged exposure. Antibiotics frequently lead to skin sensitisation if handled repeatedly. Cleanliness is the most important factor in avoiding dermatoses, but use should be made of protective clothing and forced ventilation systems.

Cancer Hazards – Some chemicals are capable of inducing cancer in humans, often some years after the first exposure. Lung fibrosis and cancer of the lung or elsewhere can arise following inhalation of asbestos and other dust. If you are unsure of the chemicals you use, find out by asking the Safety Officer for advice on short and long term toxicity.

Handling Chemicals

Virtually all chemicals are potentially hazardous. They may be flammable, toxic or corrosive. BEFORE starting any experiment you must:

  • ascertain the correct handling procedure for all chemicals used and produced in the experiment;
  • consult the MSDS for the chemicals used to determine what the hazards are and how they should be handled
  • examine each step of the proposed experiment for potential hazards and acquire the necessary safety equipment;
  • find proper procedures for safe disposal of all waste material from the experiment.
  • The above information can usually be obtained from literature. Particular caution should be exercised if there is no recorded information about the material and/or handling procedures.
  • Avoid unnecessary skin contact or inhalation of chemicals; because of the rapidity with which material may be absorbed through the respiratory passages inhalation is a particular hazard.
  • Never taste chemicals.
  • Use fume hoods for handling noxious or foul-smelling compounds and for conducting any processes that are likely to emit noxious gas, vapour, dust or mist.
  • Prevent spillages and absorption of chemicals through the skin by wearing suitable protective clothing (e.g. laboratory coat, safety glasses or goggles, proper footwear, impermeable gloves) and PROMPTLY wash off any chemicals spilt on the skin or splashed into eyes with plenty of cold water from the tap or the shower hose (see First Aid, page 14).
  • Do not sniff potentially toxic material.
  • Prevent ingestion of chemicals. NEVER PIPETTE CHEMICALS BY MOUTH, use safety pipettes, pipette fillers and automatic liquid dispensers. Do not consume food or keep food and drink in a laboratory.
  • The eyes should particularly be protected from chemicals by wearing safety glasses. If ANY chemical (especially an acid or alkali) enters the eyes they should be washed at once with a copious supply of cool water (see First Aid; page 14).

Precautions with Chemicals

Very few chemicals are completely harmless. Regard all chemicals as hazardous until you know otherwise. Protection against contamination and ingestion depends mainly on good laboratory housekeeping. The use of protective clothing is not an excuse for sloppy technique but a reminder that special care is required.

Chemicals can enter the body by three routes:

  • via the respiratory tract, due to inhalation;
  • via skin absorption from the liquid, solid or even gaseous state;
  • via gastro-intestinal tract, following accidental ingestion.

Spillage of Chemicals

Immediately clean up any accidental spillages of chemicals on benches or floor (see emergency procedures.

Spill kits are located in most laboratories which use chemicals. These kits contain vermiculite to absorb spilt liquids and sodium carbonate to neutralise acid spills. Consult Safety Officer or Manager before disposing of contaminated waste.

Whenever possible provision should always be made for certain chemicals in the event of a breakage or spillage, e.g. by working on a tray.

Solutions spilt on the bench or floor should be cleared up immediately. Strong acids being neutralised by sodium carbonate and caustic alkalis treated with ammonium chloride.

Strong nitric acid can ignite organic material therefore do not mop up un-neutralised acid on rag or paper.

Release of noxious/toxic substances into atmosphere. If noxious/toxic substances are accidentally released into the atmosphere the area should be evacuated and the room ventilated. Do not re-enter until it is safe to do so. Alert the Safety Officer and if necessary summon personnel trained in the use of Self Contained Breathing Apparatus to enter the room and clean up the spill.

Disposal of dangerous chemicals. In general dangerous, poisonous and pollution chemicals must not be poured down the sink.

Chlorinated hydrocarbons (e.g. chloroform, phenol) must NOT be poured down the drains and nor should any other organic liquid; especially those immiscible with water.

Disposal of all dangerous or poisonous chemicals should be arranged through the Safety Officer. The Safety Officer will arrange, in consultation with the RMO, for periodic collection by a registered disposal contractor.

Environmental Safety

The University has a legal obligation to ensure that there is no risk to the health and wellbeing of staff and students or to the environment when transporting, purchasing, storing and handling substances which are potentially hazardous. Delivery vehicles and visitors may bring hazardous materials, which do not belong to the University, on to the premises and the University may be held liable for any spillage and leakage to drains or subsequent injury to persons.

Violent Chemical Reactions

Many materials may react suddenly and violently with little or no warning. Particularly hazardous reactions include: Strong acids with strong bases; oxidising agents with reducing agents or metal powders; Alkali metals or earth metals with water, acids or some other solvents; Concentrate nitric acid with alcohol (reacts only after a latent period). Nitric acid should not be used for cleaning apparatus.

Ethers – Diethyl Ether is a common laboratory solvent. Ethers form explosive peroxides in contact with air and on exposure to sunlight. On evaporation any heat-sensitive peroxides present will be concentrated, and if evaporated to dryness can lead to an explosion.

The following practices are recommended:

  • Laboratory Supervisors should make their staff aware of the risk and safety phrases printed on the right hand side of the label on every bottle of diethyl ether.
  • They should be stored in dark bottles with the air space above the liquid kept to a minimum. Beware of any ether which has been in a half-filled bottle for several months. The use of clear stock bottles that are periodically topped up should be avoided for the good reasons that light encourages peroxide formation and topping-up leads to a build-up of peroxides in the bottle.
  • The bench reagent bottle should be the original bottle in which ether was supplied (e.g. the BDH 500 ml bottle) and it should be kept closed when not in use. When empty, the bottle should be discarded and replaced with a new full bottle.

Organic solvents – Most organic solvents are flammable and/or toxic and should be treated as all other flammable and toxic chemical substances. Only GLOVES suitable for a particular application should be worn – consult Ansell’s “Chemical Resistance Guide”.

To reduce the fire risk of toxic solvents the following rules should be observed:

  • Flammable solvents must be stored in a laboratory approved fire-resistant storage cabinets, sited as far away from sources of ignition as possible.
  • Reduce to the absolute minimum the quantities of flammable and/or toxic solvents used in chemical operations or held in temporary storage. Flammable solvents should be stored so as not to obstruct doorways, passages or escape routes.
  • When use of fire-risk solvents is intended, all potential sources of ignition must be kept from the working area. With ethers, the vigilance must be extreme.
  • Transport fire-risk and toxic solvents carefully in stout glassware and in quantities comfortably within your control. Winchester (2.5 L) quantities should be carried in special carriers. Do not use containers larger than Winchester (2.5 L) size.
  • Highly toxic and carcinogenic solvents should be used in fumehoods ONLY, and any spillages on skin and clothes washed off immediately (see First Aid, page 10).
  • Make sure you know where the fire extinguishers and fire blankets are, and how to use them.