An apparatus and method is provided for capturing and containing SF6 gas leakage from a gas enclosure. The apparatus includes a portage flexible gas storage container (1) of material which is substantially impermeable to SF6 gas. The container includes a gas inlet (3) which is adapted to be coupled in a sealable manner to a surface surrounding a leakage source thereby capturing the SF6 gas in thecontainer. The container inflates under pressure from the captured gas in order to accommodate up to a predetermined capacity of SF6 gas. The apparatus can be adapted to act as a container for transporting SF6 gas from a gas source to as enclosure.