Abstract: A casing safety device and method are disclosed for preventing tools from falling into an open well casing and for venting gases to a distance above the open mouth of the casing. An inflatable bladder is provided for placement in the casing adjacent the open mouth, and the bladder is inflated to block the casing and provide a stop against which falling tools come to rest. Damage to the bladder is prevented by a circular rubber shroud disposed between the bladder and the open mouth of the casing which reduces the velocity of falling objects before they strike the bladder. A vent is also provided for conveying downhole fluids, such as flammable gases, to a distance above the open mouth of the casing.