The Organisation for the Prohibition of Chemical Weapons (OPCW), which won the Nobel Peace prize last month, said its teams had inspected 21 out of 23 chemical weapons sites. The other two were too dangerous to inspect but chemical equipment had already been moved to other sites that experts had visited.
Syria "has completed the functional destruction of critical equipment for all of its declared chemical weapons production facilities and mixing/filling plants, rendering them inoperable," it said, meeting a deadline to do so no later than November 1.
The next deadline is November 15, by when the OPCW and Syria must agree to a detailed plan of destruction, including how and where to destroy more than 1000 metric tonnes of toxic agents and munitions.
Under a Russian-US-brokered deal, Damascus agreed to destroy all of its chemical weapons after Washington threatened to use force in response to the killing of hundreds of people in a sarin attack on the outskirts of Damascus in August.
Ralf Trapp, a chemical weapons disarmament specialist, said: "This is a major milestone in the effort to eliminate Syria's chemical weapons programme."