topic 3: chemical hazards and safety

• Globally harmonized system of classification and labelling

  (GHS)

  • system developed by the UN for consistent chemical hazard communication
  • protect humans and the environment against hazardous chemicals and facilitate international trading of chemicals
  • provides a recognized framework for countries without an existing system and reduced the need for testing and evaluation of chemicals
  • implemented in SG subce 2016
• 3 types of chemical hazard classifications and their hazard classes

  1. physical hazard - 16 hazard classes
  2. health hazard - 10 hazard classes
  3. environmental hazard - 3 hazard classes

  a lower hazard category number indicates a mroe hazardous chemical
• chemical hazard classification

  • chemicals are assigned GHS pictograms to idetify and classify them associated hazards (corrosion, etc.)
  • 9 types of pictograms
  • each pictogram conveys the hazardous properties and hazard severity of a chemical
• the 9 pictograms:

  1. flame over circle - oxidisers
  2. environment - environment toxicity
  3. exploding bomb - explosives/ organic peroxide/ self-reactives
  4. skull and cross bones - acute toxicity (severe)
  5. corrosion - corrosives
  6. gas cylinder - gases under pressure
  7. health - aspiration toxicity/ carcinogenicity/ respiratory sensitisation
  8. flame - self-heating/ organic peroxides/ aerosols
  9. exclamation mark - acute toxicity / irritant/ hazard to ozone layer
• the physical hazards

  generally refers to chemical substances that can cause combustion, fire and explosions.

  1. oxidiser (gases/liquids/solids)
  2. explosives (organic peroxides, self reacting substances/mixtures)
  3. corrosive (metals)
  4. flammable (gases, aerosols, liquids, solids, some subst, when in contact w water emit flammable GAS)
  5. gases under pressure
• health hazards:

  1. acute toxicity (short term toxic effects on humans, respiratory/skin)
  2. harmful
  3. corrosive (skin/eye irritation)
  4. toxicity(germ cell mutagenicity, carcinogenicity, repro, aspiration hazard)
• environmental hazards

  1. harmful
  2. environmental hazards (aquatic env/ ozone layer)
• safety data sheets (SDS)

  • each chemical has one
  • written by manufacturer
  • covers wide range of info to ensure safe handling and response
  • manufacturer: provide updated SDS, physical/digital (5 year validity)
  • occupier: check validity of SDS, conduct risk assessment, file SDS
  • user: refer to SDS before use, take precautionary measures
• 16 sections in SDS

  identification:name,composition, supplier details

  hazard identification: GHS pictogram, percautionary statement

  A) what is needed to identify chemical?

  B)

  C)

  D) injury

  E) flammability

  F) toxicity

  G) how to keep?

  H) personal safety

  I) acid/base

  J) extent of reactiveness

  K) toxicity

  L) environmental hazard?

  M) how to dispose?

  N) how to send it?
• signal word and preventative measures for: corrosive

  DANGER

  • wear protective gloves,clothing,eye protection, face protection
• chemical product labelling (labelling inclues...)


  1. product name
  2. GHS pictogram
  3. signal word
  4. hazard statement
  5. precautionary statement
  6. supplementary info
  7. supplier info
• dimensions of labels

  the larger the dimentions, the larger the label

  if bottle is too small, only product name and pictogram is needed(these cannot be supplied to another workplace,info is incomplete)
• general safe handling and use of chemicals

  • chemicals shall be used in process specifications and only by trained personell
  • standard operating procedures must be in place
  • hazardous chemicals must eb mixed/poured in chemical fume hood(preventing inhalations of fumes/vapors)
• good house keeping

  • no smoking, eating, drinking where chemicals are stored/handled
  • suitable PPE must be worn
  • emergency response team must be organized to handle chemical spills
• storage of chemicals

  • breakable chemical containers should be stored in a secondary container
  • all chem containers shld be dated when recieved/opened
  • chem storage areas with facilities for emergency response
  • when not in use, all chemicals should be locked to keep away from unauthourised personels
• DO NOT store chemicals at...

  1. on the floor
  2. on workbench
  3. abover eye-level
  4. in fume hood
  5. in excessive quantity
• DO store chemicals at...

  • away from sources of heat
  • properly labelled
  • by compatibility then alphabetical order
  • in proper cabinates fro segregation
• storing flammable chemicals

  • protects flammable chemcials from ignition source
  • store in 1hr-fire rated storage cabinate away from heat source or in a cool, well-ventilated area
  • DO NOT store w oxidizing chemicals/ reactive chemicals
• storing corrosive chemicals

  these chemicals have either a very low or very high pH, when in contact w moisture/water, inhaling corrosive vapour or mist can cause severe irritation of damage to respiratory tract

  • store at low shelves and in a secondary container to minimize spill/damage/injury
  • use cabinets specific for corrosives

  DO NOT store alkalis tgt (can react violently when mixed)

  DO NOT store acids w flammable chemicals (most acids are oxidisers)
• storinf gaseous chemicals

  usually compressed gas cylinders. poses both physical and chemical hazards

  • store in minimum quantitiesw labels indicating "full", "in use", "empty"
  • stationary gas cylinders shall be secured w safety chains to prevent moving/ falling over
  • DO NOT store near heat source and potential physical damage
  • DO NOT store w incompatible gases
• transporting chemicals

  • incompatible materials shall not be transported on the same cart
  • open containers shall not be transported
  • bottles shall be transported on the cart with side rails and secondary containment capable fo containing spills
• proper disposals of waste chemcials

  • all waste chemicals shall eb disposed in accordance to regulations of the NEA
  • do not pour into public sink
  • each container of liquid waste must be palced in 'secondary containment'
  • contents of waste bottles shld be written clearly
• hieraachy of risk control measures for chem hazards

  1. elimination
  2. substitution
  3. engineering controls ( implemetn phsyical changes to the workplace)
  4. administrative controls
  5. personal protective equipment (use protection to reduce exposure to risk factors)
• 16 sections of new SDS cover

  1. identification
  2. hazards identification
  3. information of ingredients
  4. first-aid measures
  5. fire-fighting measures
  6. accidental release measures
  7. handling and storage
  8. exposure controls / PPE
  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