Chemical Safety / Particularly Hazardous Chemicals

Particularly Hazardous Chemicals

The use of particularly hazardous chemicals requires extra safety precautions and work with these chemicals should only be done after consultation with your supervisor.  Users must be aware of the hazards posed, and the procedures implemented to control them, prior to working with these chemicals. This often requires extra or specialized training (e.g. Radiation and Biosafety courses offered by EHS) intended to provide a clearer understanding of safe storage practices, labeling procedures, safe handling practices, including transferring and use of equipment and apparatuses (glove boxes, gas cabinets etc.), engineering controls, selection and use of PPE and, emergency procedures. Work with these chemicals must be in designated areas and it is important that those around you are informed of the materials that you are working with so that that they too can take proper precautions.


  • Toxic or Highly Toxic Chemicals – chemicals with high acute local or systemic toxicity, or chronic toxic effects such as carcinogens, reproductive or developmental toxins, and mutagens.
  • Highly Reactive and Explosive Chemicals - chemicals that have the potential to vigorously polymerize, condense, or become self-reactive due to shock, pressure, temperature, light, or contact with another material.  The result is generally a violent release of energy with a large volume of gas, heat, and possibly toxic vapours.  Failure to observe the appropriate handling procedures can lead to fire or explosion that can cause serious injuries and property damage.

o   Explosives Chemicals (Shock/Heat Sensitive) - chemical that causes sudden, almost instantaneous release of pressure, gas, and heat when subjected to sudden adverse conditions. Heat, light, mechanical shock, detonation, and certain catalysts can initiate explosive reactions. Compounds containing the functional groups azide, acetylide, diazo, nitroso, haloamine, peroxide, or ozonide are sensitive to shock and heat and can explode violently.

o   Pyrophoric Chemicals - ignite spontaneously when exposed to air.  Also tend have corrosive, water reactive, and peroxide forming properties.

o   Water Reactive Chemicals - react with water or moisture in the air to give one or more of the following outcomes:

1.   Liberation of heat, which can cause the ignition of the chemical itself, if it is flammable, or other flammable chemicals nearby.

2.   Release of flammable, toxic or strong oxidizing gases.

3.   Formation of corrosive acids.

  • Alkali metals, alkaline earth metals, carbides, hydrides, inorganic chlorides, nitrides, and peroxides are water reactive.

o   Peroxide-Forming Chemicals. A number of chemicals can become dangerous with age due to a tendency to form peroxides when exposed to air, moisture, and other impurities. Peroxides, and the chemicals that contain them, are sensitive to heat, shock and friction, and may explode violently. Organic Peroxides are some of the most hazardous chemicals used in laboratories because, in addition to being sensitive, they readily react with oxidizing and reducing agents and are highly flammable. There are three groups of peroxides:

A.  Spontaneously form peroxides with exposure to air without further evaporation or concentration. Test for peroxides or dispose of within 3 months of opening.

B.   Form peroxides only upon concentration by evaporation or distillation. Test or dispose of within 1 year of opening.

C.   Monomers that form peroxides that may act as a catalyst, resulting in explosive polymerization.

  • The more volatile the compound the greater the hazard because evaporation allows the peroxide to concentrate.
  • Protect containers from heat sources and physical damage.
  • Do not store peroxide forming chemicals at low temperatures where peroxides may precipitate out, making them more susceptible to shock. When necessary to cool, an explosion proof refrigerator must be used.
  • Inspect the containers of peroxide forming chemicals frequently for signs of peroxide accumulation.  If any of the following are present, do not move the container and seek help with removal:

*    Liquid chemicals: Look for crystal formation around the cap or in the liquid itself, discoloration, or viscous liquid at the bottom of the container.

*    Solid chemicals: Look for discoloration or a surface crust.