A chemical weapons expert involved in the apparent discovery of continued chemical weapons attacks in Syria told ITV News earlier this week that chlorine use is "simple to identify".
Hamish De Bretton-Gordon told Diplomatic Correspondent John Ray that Syrians should be armed with information on how to identify such attacks.
He added, however: "It's very, very non-persistent - once it's released it will remain active for, at the most, minutes.
"If there is a strong wind and if it is hot as it is in Syria it will disappear very quickly."
More top news
The government has announced plans to ensure staff receive tips left by customers in bars and restaurants.
Tens of thousands are having do not resuscitate orders imposed without families' consent, according to the Royal College of Physicians.
The prime minister has said the debate over Britain's EU membership has affected his long-term friendship with the mayor of London.