Schedule 3 substances, in the sense of the Chemical Weapons Convention, are chemicals which can either be used as toxic chemical weapons themselves or used in the manufacture of chemical weapons but which also have legitimate large-scale industrial uses.
Plants which manufacture of more than 30 tonnes per year must be declared and can be inspected as per Part VIII of the "Verification Annex", and there are restrictions on export to countries which are not CWC signatories. Examples of these substances are phosgene, which has been used as a chemical weapon but which is also a precursor in the manufacture of many legitimate organic compounds and triethanolamine, used in the manufacture of nitrogen mustard but also commonly used in toiletries and detergents.
As with the other schedules, they are sub-divided into Part A substances, which are chemicals that can be used directly as weapons, and Part B which are precursors useful in the manufacture of chemical weapons.
Chemicals which can be used as weapons, or used in their manufacture, but which have no, or almost no, legitimate applications as well are listed in Schedule 1, whilst Schedule 2 is used for chemicals which have legitimate small-scale applications.
The criteria for including a chemical in this schedule is that it is not listed in either of the other two, and: