An improved system and a device for providing air inflated cushioning material which is filled and sealed at the site of its intended use, such as at a packaging line. Included is an elongate flexible layered strip material comprising two heat sealable films fused together in discrete areas to form two rows of inflatable chambers along the strip and a passageway extending the length of the strip between the rows, with each of the chambers having an inlet opening narrower than the main portion of the chamber communicating with the passageway. The strip is shipped uninflated to the site where the cushioning material is to be used, and is then inflated on the device through which the passageway in the strip is propelled over an air nozzle to inflate the chambers through their inlet openings. The device heat seals the inlet openings after first pressing together and tensioning the films around the area to be sealed to both insure a wrinkle free seal and insure that air pressure in the chamber will not rupture the sealed area while it is hot.