It's more likely that a rebel held weapons cache, which included chemical weapons (!), blew up and released the gas. We don't know what caused the initial explosion, although it could have been a bomb or missile from the Assad forces trying to destroy the cache.
Great independent thinking & an original theory you've come up with there. Clearly you don't get you opinions spoon fed to you by Russians and their compliant media.
Russian Defense Ministry spokesman Igor Konashenkov stated that the Syrian air force struck a munitions factory east of the town, where rebels were producing shells filled with toxic gas to be sent to Iraq. He added that Islamist militants had used similar chemical weapons last year during the fighting in the city of Aleppo.
