On the day of the suspected chemical attack, Douma was still under the control of the Jaish al-Islam group, the last rebel bastion in the Eastern Ghouta region outside Damascus.
The team from the Organisation for the Prohibition of Chemical Weapons (OPCW) travelled to the town of Douma and collected samples and other items.
Media playback is unsupported on your device Media caption A short guide to the Syrian civil warInternational chemical weapons experts have finally inspected the site of a suspected attack near Damascus which caused an international crisis.
Last week Western states bombed several Syrian government sites in retaliation for the suspected attack on 7 April.
In a statement, the Russian foreign ministry accused the OPCW of itself taking too long to inspect the suspected attack sites.