An example is thiodiglycol, which can be used in the manufacture of mustard agents but is also used as a solvent in inks.
Manufacture must be declared as their production is subject to declaration to the Organisation for the Prohibition of Chemical Weapons (OPCW) per Part VII of the "Verification Annex", and they may not be exported to countries that are not party to the Convention.
Chemicals that can be used as weapons, or used in their manufacture, but that have no, or almost no, legitimate applications as well are listed in Schedule 1, whilst Schedule 3 is used for chemicals that also have widespread industrial uses.
The use of Schedule 1, 2, or 3 chemicals as weapons is banned by the Convention.
Schedule 2 lists toxic chemicals and precursors – not listed in Schedule 1 – that are deemed to pose a significant risk to be used as a chemical weapon, or may be important for the production of any of the chemicals listed in Schedule 1.