An access device for containers of fluidizable substances includes a body provided with a hollow spike designed to be inserted into a container of a substance to fluidize and having an axial fluid passage and an axial passage for venting of the container, an expandable chamber connected to the venting passage of the spike through a lateral passage of the body, a first check valve enabling one-way communication from the lateral passage to the expandable chamber, a second check valve enabling one-way communication from a vent opening to the venting passage of the spike. A double impermeable filtering membrane is interposed between the first check valve and the second check valve.
