Blood samples that have been contaminated by Hepatitis B viruses should be tagged with this symbol.
Heating or dropping could cause these cylinders of pressurized gas to explode.
Industrial cleaners containing sodium hydroxide, a very corrosive base, should have this symbol on their label.
The fact that most aerosol cans have propellants that can be ignited easily means that this symbol should be on their labels. Since it poses such a fire hazard a bottle of methanol would have this symbol on it' s label.
By releasing oxygen, can cause a flammable material to burn more easily.
This material could kill you if swallowed, inhaled, or absorbed through the skin.
Some chemicals bearing this symbol can undergo a dangerous reaction if they come in contact with water.
Chemicals in this devision won't kill you immediately, but could cause such unwelcome effects as birth deffects in your children or liver damage. A chemical that causes cancer after prolonged and repeated exposure would get this symbol on it's label.