Russian officers visited the site of the supposed chemical attack and found no trace of any chemical use.

https://www.rt.com/news/423627-russian-military-checks-chemical-douma/

Russia also blames the UK for staging the "provocation" having interviewed some of the people there.

"During the provision of first aid, unknown people ran into the hospital, some of them with video cameras, who started screaming, panicking and pouring everyone with water from hoses, shouting that everyone was poisoned with toxic agents. Patients… and their relatives in panic began to pour water on each other,"
https://sputniknews.com/russia/201804131063516609-russia-douma-chemical-incident/