Abstract: The invention provides an apparatus and a method for suppressing ignition of flammable materials in a borehole. The apparatus may include a down hole device having an upper end and a lower end, with a shaft extending between the upper and lower ends. A flexible sheath is carried about the shaft. The sheath is upwardly open to atmosphere and is sealed from the borehole adjacent its bottom end. A gas-receiving gap is defined between the sheath and the shaft. A cap seals the annulus between the borehole's wall and the flexible sheath, with the cap desirably sealingly engaging the sheath adjacent its upper end. An inert gas delivered to the gas-receiving gap through a delivery conduit. In one method of the invention, an apparatus as outline above is provided. The down hole device is placed in a borehole such that its upper end is positioned adjacent ground level and its lower end is positioned within the borehole.