Abstract: An apparatus for acetone clearing of cellulose or nitrate membrane filters includes an elongated electric heater element with tubing for transporting acetone coiled around said heater element and in contact therewith. Liquid acetone is introduced to said tubing wherein it is heated by said heater element and acetone vapor is discharged from said tubing. The temperature of the coiled tubing is thermostatically controlled. Acetone vapor is removed from said tubing and passed over a glass slide having an exposed filter containing particulars, such as asbestos fibers. The vapors clear the filter to render it translucent for examination in optical microscopy.

Abstract: A pressurized source of fluid, either liquid or gas, is supplied through a supply conduit system to a main heat sensitive conduit fabricated from a thermoplastic material and having sealed end portions positioned adjacent a potential source of fire or undesirably high temperature. A plurality of branch heat sensitive conduits are connected to the main conduit and extend therefrom into substantially abutting relation with the object to be monitored. The supply conduit system maintains a selected fluid pressure within the heat sensitive conduits which are operable to soften and rupture at a preselected temperature, as determined by the system pressure and the diameter and wall thickness of the heat sensitive conduits. When exposed to the excessive preselected temperature, the conduits rupture.