Abstract: A hollow body with an internal supporting frame (10) which is connected to a housing (14) at at least two contact points. The housing and the supporting frame are made of synthetic resin material with the housing, which is produced by blow molding, enclosing the supporting frame.

Abstract: In a vent arrangement comprising a heating cylinder 1 containing therein a screw and provided with a vent hole 3 and a reduced pressure exhaust path 4 provided with a vacuum pump and connected to the vent hole 3 for draining volatile fractions of a material to be molded from the heating cylinder by reducing the pressure in the vent hole by means of the vacuum pump, said volatile fractions are removed by arranging in the exhaust path a filter unit 7 filled with a granular filtering material 8. The material to be molded is used for the filtering material 8. According to the above construction, it can be achieved to efficiently remove volatile matters by using the molded material as the filtering material of the filter unit arranged in the reduced pressure exhaust path of a vent arrangement.

Abstract: Improved anisotropic fluid separation membranes are prepared from blends of polymers with surface energy differences. The membranes are formulated by processes wherein low surface energy polymer with desirable fluid separation and permeation characteristics is preferentially concentrated in the surface discriminating layer of the membrane.

Abstract: The present invention discloses an improved method for filtration of air within enclosed spaces. Improvement is achieved by the use of a high-temperature carbonaceous char that is catalytically active for the removal of certain undesirable constituents from contaminated air under ambient temperature conditions. This carbonaceous char is used as an air filtration medium and incorporated into an air filtration device by any of a number of technologies. Such devices may be used for removal of contaminants such as NO.sub.x, NO.sub.2, SO.sub.x, SO.sub.2, H.sub.2 S, mercaptans, light aliphatic gases such as butane and propane and other compounds such as benzene, hexane, toluene, xylene, amines and the like from enclosed or confined structures such as buildings or vehicles including automobiles, aircraft, trucks, farm equipment, and the like.

Abstract: A vacuum truck includes a storage tank mounted on the truck frame and a vacuum pump for drawing air into the storage so that a vacuum hose extending from material to be excavated to an inlet of the storage tank carries the material into the tank for discharge from the air prior to passage of the air to vacuum pump. A filter system is provided in the ducting between the storage tank and the vacuum pump to extract particles and moisture from the air. The filter system includes a chamber attached along one side of the cylindrical storage tank with that chamber having a plurality of curtains attached to an upper wall of the chamber and suspended vertically across the chamber. Each curtain is formed from a plurality of chain lengths suspended by a top link of the chain to a bracket at the top wall of the chamber. The lengths are arranged side by side to form a full curtain across the width and height of the chamber.

Abstract: A method of using water soluble foamed starch for reclaiming paint overspray particles from air includes the steps of passing a stream of air containing paint overspray particles through an air filter assembly having a filtration element. The filtration element consists essentially of water soluble foamed starch. The paint overspray particles are collected on the filtration element. The filtration element containing the collected paint overspray particles is deposited in a vessel containing water. The filtration element is dissolved in the water and an aqueous solution of starch in water is formed. The paint overspray particles are separated from the aqueous solution of starch dissolved in water.

Abstract: The present invention discloses an improved method for filtration of air within enclosed spaces. Improvement is achieved by the use of a high-temperature carbonaceous char that is catalytically active for the removal of certain undesirable constituents from contaminated air under ambient temperature conditions. This carbonaceous char is used as an air filtration medium and incorporated into an air filtration device by any of a number of technologies. Such devices may be used for removal of contaminants such as NO.sub.x, NO.sub.2, SO.sub.x, SO.sub.2, H.sub.2 S, mercaptans, light aliphatic gases such as butane and propane and other compounds such as benzene, hexane, toluene, xylene, amines and the like from enclosed or confined structures such as buildings or vehicles including automobiles, aircraft, trucks, farm equipment, and the like.

Abstract: Add-on filters for heated-air blowers and other electric motor-powered appliances. The filters are fabricated from a washable, flexible, reticulated foam which traps even minute solid and liquid particles and is adhesively attached to the blower housing. A template, which also serves as a protective cover for the adhesive, has index lines along which a blank of the filter material can be trimmed to size and configured for a particular blower intake.

Abstract: A porous polytetrafluoroethylene (PTFE) structure particularly for use as a liquid filter comprises particles of granular-type PTFE fused together to form a porous integral network. The structure is formed by spraying an aqueous suspension of granular PTFE particles and baking at a temperature of 335.degree.-350.degree. C. Typically the specific gravity is 0.8 to 1.54. The crystallinity is less than 95%. The structure may be supported on a perforate substrate such as stainless steel mesh.

Abstract: A micropore filter of discrete flow-through pores of highly controlled pore configuration and dimensions is formed by bonding platelets into a laminate, each platelet having been etched, preferably by a combination of electropolishing and photoetching techniques, to form depth-etched passages and through-etched passages, respectively. The filter is housed in a module which contains wiper blades for periodically removing deposited debris from the filter surface.

Abstract: A wool filter for a dust-proof mask is disclosed, in which wool fibers are mixed with chemical resin film slitting yarns so as to manufacture a non-woven fabric, thereby doubling the electrostatic force to improve the dust filtering function. In manufacturing the wool filter for a dust-proof mask, 40 to 90 weight % of wool yarns is uniformly mixed with 10 to 60 weight % of chemical resin film slitting yarns, preferably polyolefinic resin film slitting yarns.

Abstract: An air cleaning apparatus includes an air passage chamber having a suction port, from which air is sucked, and a discharge port from which the air sucked from the suction port is discharged, an air blower, provided in the air passage chamber, for sucking the air from the suction port into the air passage chamber and discharging the sucked air from the discharge port, and a particle removing mechanism for removing particles contained in the air sucked from the suction port, the entire body of the particle removing mechanism being formed of a material which generates little impurity gas detrimental to processing in a processing space.

Abstract: A circular filter cartridge for air pollution control has a plurality of pleats 10 so arranged on fold lines as to define an inner end section 20 for each pleat on the periphery of a circle 22 of a first diameter, and outer sections 24 extending between adjacent pleats lying on the periphery of a further circle 26 of increased diameter. By providing flat surfaces, dust or other pollution does not build up at any particular point on the filter and also wear on the cartridge is reduced, leading to a more efficient and cost effective filter cartridge. Lower pressures of compressed air or liquid can also be used for cleaning.

Abstract: The filter device (10) has a filter element (12) including a filter medium (20) arranged in zig-zag shaped pleats. On its two longitudinal sides extending in the pleating direction (36), the filter medium (20) is provided with stabilizing strips (34) bonded thereto for stabilizing the zig-zag-shaped pleated configuration of the filter medium (20). During use of the filter device (10), the filter element (12) is arranged within a filter element holding frame (14) which is inserted in a holding members, e.g. in the air inlet shaft (18) of an air conditioning system. Due to a certain inherent stability of shape of the filter medium (20) and the stabilizing strips (34), the filter element (12) is sufficiently firm and has a self-supporting construction. The filter element (12) is easy to handle and can be inserted into the filter element holding frame (14) in a simple manner. Except for the actual filter medium (20), the filter element (12) requires little extra material, i.e.

Abstract: An improved filter unit suitable for use in a variety of clean air filtration applications is taught. The filter unit employs continuous microporous filtration membranes, such as expanded polytetrafluoroethylene, to deliver exceptional filtration efficiencies on the order of 99.99999% at 0.1 .mu.m with minimal pressure drop produced across the filter. Additionally, the filter unit of the present invention has the further advantage of avoiding many previous deficiencies in HEPA and ULPA filter units, such as filter contamination from shedding particles and/or out-gassing, and limitations on chemicals to which the filter can be exposed without deterioration. As a result, the present invention provides a cleaner and more durable filter that can be used to address growing contamination problems in many different industries, such as electronics and pharmaceuticals.

Abstract: Aminated polymers capable of reversibly complexing carbon dioxide and other acid gases including CO.sub.2, SO.sub.2, NO.sub.x and H.sub.2 S, a method of using such polymers and an operational unit including such polymers are disclosed. The polymers incorporate amine group which reversibly complex acid gases. Such polymers provide a significant advantages over presently used sorbents used to remove acid gas.

Abstract: A paint arrestor for absorbing paint overspray comprises a series of layers of sheet material, each of the layers being slit and expanded to define an array of air spaces distributed in columns. The air spaces alternate in size from column to column and repeat in size in every other column. Means are provided for securing the layers in contiguous, overlying relationship with one another.

Abstract: A magnetic filter material is disclosed. The filter material according to the present invention comprises a spray-spun, self-bonded, nonwoven fibrous structure consisting essentially of 40 to 99% by weight of a polymer selected from the group consisting of polycarbonate, polyethylene, polypropylene, polyamide, polyimide, polyester, polytetrafluoroethylene and polyacrylonitrile and 1 to 60% by weight of a magnetic substance selected from the group consisting of barium ferrite, strontium ferrite and samarium-cobalt.The magnetic filter material of the present invention shows excellent filtration efficiency of metal impurities such as iron, iron oxides, and other metal dusts due to have a dual function by physical porosity and magnetic attraction, and thus is suitable as an air and oil filter medium for automobiles and other industrial machinery, a liquid filter medium for treating industrial waste water and oil, a filter medium in dust collecting and air-conditioning systems, and so forth.

Abstract: A meshed plastic filter of a narrow-pitch net with a net structure and a frame structure formed in either a square or a circular overall shape into a plastic injection molded unitary body includes a dam/discharge rib in the net structure for storing molten plastic material and accumulating pressure of the molten plastic material, thereby enabling implementations of a fine-pitch net filter having mesh holes of 0.2 mm in diameter at a spacing of 0.3 mm, which has diverse applications, such as a filter or sieve for gasoline or oil, a dust collector filter and other various filtration.

Abstract: A filter apparatus having a filter bag subassembly for collecting contaminating material. The filter bag sub-assembly includes five diametrically and axially-spaced bags and an integral collar. The five spaced bags form five spaced chambers and the integral collar has a stepped shape forming five cylinder support portions for the five spaced bags.

Abstract: A noise attenuating air cleaner assembly for an internal combustion engines or the like operating in a dusty environment. The air cleaner assembly having a silencer assembly arranged concentric inside an air filter cartridge assembly and a noise attenuating end wall assembly closing an end of the air filter cartridge assembly attenuating air cleaner assembly to provide a source of clean air to the engine and to reduce transmitted induction noise.

Abstract: A method of manufacturing a water barrier fabric, in flexible or rigid form, and articles manufactured thereby, formed by dispersing a water-absorbent material, in powdered or granular form, among a mass of fibers during the formation of a loose mat of said fibers, to homogeneously disperse the powdered or granular water-absorbent material above, below and on each side of the fibers forming the mat, and thereafter densifying and structurally consolidating the mat, to secure the fibers in position surrounding and entrapping the water-absorbent material, such as by sewing, quilting, needle punching or otherwise bonding the fibers into a consolidated, structurally secure fabric at least partially filled with the powdered or granular water-absorbent material. In a preferred embodiment, one, or both, major surfaces of the fabric is coated with a water-insoluble adhesive to substantially increase the tensile strength of the fabric and to prevent shifting of fibers when installed on sloping surfaces.

Abstract: A fluid filtration material made of a porous substrate, e.g. a membrane or a fabric, that is coated with a fluorinated copolymer that contains recurring vinyl alcohol units that have been reacted with a monoepoxide to aid in preventing loss of hydrophilicity in the coated material.

Abstract: An expanded fiber composite structure and process for making an expanded fiber composite structure are provided. The expanded fiber composite structure is made up of a fiber mat held in partial compression by a monolithic plastic coating on the fibers, the structure having a plurality of interstitial voids which may optionally be filled with a polymeric interstitial material. The process includes impregnating a fiber mat with a plastic material, compressing the mat to impregnate the mat with the plastic, fully wetting each fiber and creating a substantially void-free fiber/plastic matrix, and reducing the compressive forces on the mat, allowing the fibers to rebound and expand the mat to a predetermined desired thickness, in the process creating the interstitial voids. The structure is then cooled such that the plastic material stiffens and itself retains the structure at the desired thickness.

Abstract: Provided are molded adsorbents comprising a mixture of adsorbent particles, fine plastic particles and a reinforcing fiber, the mixture having been molded utilizing the fine plastic particles and, as required, the reinforcing fiber as binder. They have features, as compared with conventional molded adsorbents utilizing a latex binder, having an adsorptive capacity having been decreased to a smaller extent from those of the raw material adsorbent particles used and higher adsorption rate owing to well-maintained porosity. They have good mechanical properties at normal temperature and can hence be processed by cutting or like machinings into various machine parts, including blades of fans having both adsorptive capacity and high mechanical properties. Also provided are a process for producing the above molded adsorbents and their use as deodorizing units.

Abstract: A catalytic air cleaner purifies air in enclosed spaces, such as in an aircraft or spacecraft. The air cleaner includes a pair of metal strips, wound into a double spiral. The strips have projections, affixed to the strips, to maintain the spacing between turns of the spiral. The spiral defines a core which accommodates an electrically heated catalytic converter. The strips themselves have no catalyst coating. A pair of ports at the periphery of the spiral allows air to enter and leave the spiral through inlet and outlet channels. Air entering the spiral through the inlet channel receives heat, by heat exchange, from air leaving the spiral, and then enters the core, where the electrically heated catalytic converter burns off various impurities. The air then leaves the spiral through the outlet channel, and becomes cooled by transferring its heat to the incoming air.

Abstract: An air filter assembly for an engine such as a chain saw engine. The filter assembly includes a cage, a foam filter having a sidewall surrounding a sidewall of the cage, a retaining member pressing an endwall of the filter against an endwall of the cage and a nut. The nut receives a threaded end of an anchor bolt passing through axially aligned holes in the endwalls of the cage and the filter and a hole in the retaining member. The filter assembly provides high flow rates therethrough and substantially avoids penetration of dirt around the nut connection.

Abstract: A filter element is disclosed which serves to separate dusts from gases or air and consists of metals, alloys or plastics. The element is thin-walled and sheetlike, has a wall thickness of 0.05 to 2 mm and has a large number of regularly arranged holes, which have any of various shapes and sizes and have a non-circular cross-section and a hydraulic diameter of 0.01 to 1 mm. In that filter element the area which is occupied by the holes is 3 to 25% of the front surface area of the filter element.

Abstract: An air filter assembly for an engine such as a chain saw engine. The filter assembly includes a cage, a foam filter having a sidewall surrounding a sidewall of the cage, a retaining member pressing an endwall of the filter against an endwall of the cage and a nut. The nut receives a threaded end of an anchor bolt passing through axially aligned holes in the endwalls of the cage and the filter and a hole in the retaining member. The filter assembly provides high flow rates therethrough and substantially avoids penetration of dirt around the nut connection.

Abstract: A filtering device includes a head intended to be permanently installed in a fluid dispensing machine and a disposable canister therefor. A central chamber is formed in the head which chamber is in communication with an inlet port and an outlet port for receiving an unfiltered liquid and supplying a filtered liquid, respectively. The disposable canister has a flask shaped main body with a flat top and a neck of substantially uniform diameter on the top. The neck fits in the central chamber. A tube extending through the neck defines an annular clearance between the tube and the interior of the neck which annular clearance is in fluid communication with the inlet port. The opening into the tube located at the top of the neck is in fluid communication with the outlet port in the head. A pair of tab receptacle on the head and a complementary pair of tabs on the canister are engageable with one another by 1/4 rotation of the canister to lock the canister to the head.

Abstract: A method for lining a porous tube (5) with a film (11) of SiO.sub.2 is described. The treated tube may be used to separate hydrogen from reaction mixtures such as those resulting from the water-gas shift reaction or the catalytic decomposition of hydrogen sulfide.

Abstract: A filtering device includes a head intended to be permanently installed in a fluid dispensing machine and a disposable canister therefor. A central chamber is formed in the head which chamber is in communication with an inlet port and an outlet port for receiving an unfiltered liquid and supplying a filtered liquid, respectively. The disposable canister has a flask shaped main body with a flat top and a neck of substantially uniform diameter on the top. The neck fits in the central chamber. A tube extending through the neck defines an annular clearance between the tube and the interior of the neck which annular clearance is in fluid communication with the inlet port. The opening into the tube located at the top of the neck is in fluid communication with the outlet port in the head. A pair of tab receptacles on the head and a complementary pair of tabs on the canister are engageable with one another by 1/4 rotation of the canister to lock the canister to the head.

Abstract: A process for producing a filter including a microporous membrane and a supporting structure connected thereto, including producing a mold for the membrane and the supporting structure, filling the mold with a molding material whose solubility can be changed by high energy radiation, and forming the micropores by partial irradiation of the membrane with high energy radiation and removal of the regions having increased solubility. The filter produced according to the above method is a unitary structure with the supporting structure integrally connected to the membrane.

Abstract: A container for adsorbing components present in an environment, which comprises a tubular structure of expanded, porous polytetrafluoroethylene sealed at both ends, so as to encapsulate an adsorbent present with the tubular structure.

Abstract: A gas mask filter material is described comprising a dried acidic ion exchange resin which is effective in removing low levels of ethylene oxide from air contaminated therewith. Specifically described is a gas mask filter comprising a cross-linked polystyrene resin with sulfonic acid functionality that contains less than about 20 percent by weight water.

Abstract: An evaporative fuel control canister device containing a quantity of fuel-absorbing material which includes EPDM elastomeric foam for improved absorption of both fuel vapor and liquid fuel.

Abstract: This invention provides a material for gas separating membrane comprising a fluorine-containing acrylate or methacrylate polymer or a crosslinked compound of the polymer.

Abstract: Disclosed is the filtration of fluids by utilizing porous biogenetic silica ash devoid of fiber alone or combined with additives. The biogenetic silica may be in particles or prilled or pelleted. Solid particles and liquids are filtered from gases and liquids by passing them through the biogenetic silica. The additives are materials which attract the impurities into the pores of the biogenetic silica, such as water-swellable polymers or carbon remaining on the biogenetic silica when incompletely pyrolyzed. The carbon can be activated.

Abstract: An air filter comprising a first layer of reticulated foam plastic material having a thickness of between 10 mm and 20 mm and a porosity of between 5 and 60 pores to the linear inch, a second layer of reticulated foam plastic material having a thickness of between 6 mm and 10 mm and a porosity of between 60 and 100 pores to the linear inch, and at the interface between said first and second layers an open mesh substrate approximately one millimeter in thickness constricting a maximum of about ten percent of each of the first and second layers, the filter being impregnated with a flame proof retention and plasticizer additive, the first and second layers being bonded together at the interface.

Abstract: A process for producing dense membranes comprises allowing a solution comprising a polar polymer and/or a polar prepolymer in a polar solvent which is substantially soluble in a polar liquid to spread out over the surface of the polar liquid and allowing the spread out solution to desolvate. The dense membranes can be applied in supported membranes for use in gas separation processes.

Abstract: The invention relates to films and tubular structures which are selectively permeable to liquids and gases which are based on a copolymer composed of a copolymerized fluorinated olefin, copolymerized vinyl acetate and, optionally, a copolymerized olefin. It is possible for the acetate groups of the copolymer to have been saponified to form OH groups. The films or tubular structures have in each case an inherent, latent capacity for modifying their structure and are at the same time oleophobic and oleophilic. The invention also embraces processes for the preparation of the shaped articles described and processes for modifying their structure. The invention also relates to the use of shaped articles according to the invention.

Abstract: The present invention provides an apparatus and process for separating and removing chemical impurities from air which impurities are difficult to absorb. The apparatus for carrying out the process of the present invention comprises a reaction tower (11, 51, 91) into which the air-gas mixture is fed, aperture means (35, 74, 96) in a wall (16, 60, 98) of the tower, at least one filter means (12, 52, 92) carried in the reaction tower, means for distributing (13, 58, 93) an absorbent medium onto the filter, collecting means (14, 54, 94) beneath the filter for collection of the absorbent medium passing through the filter, and fan means (15, 55, 95) provided in the aperture for creating a flow of air through the reaction tower for the separation of substantially all of the impurities therefrom.

Abstract: The invention provides an air cleaner assembly in combination with an engine having a blower housing with airflow circulating therethrough and a carburetor having an intake. The assembly comprises a duct having an inlet and an outlet with the inlet angularly disposed through the blower housing, an air cleaner housing having side walls and a bottom wall, and an outlet chamber having an inlet and an outlet in communication with the carburetor inlet. Within the air cleaner housing, a first interior wall is upstanding from the bottom wall and defines with certain side walls an intake chamber having an inlet communicating with the duct outlet, and a second interior wall upstanding from the bottom wall so that a filter chamber is formed between the interior walls having an outlet in its bottom wall so that the filter chamber and outlet chamber communicate through the filter chamber outlet and the outlet chamber inlet.

Abstract: Hot gas filter for separating solid particles carried along in high temperature or waste gases having a filter casing made of heat-resistant brickwork, in which there is provided at least one oblong filter cell one end of which ends in a hot gas supply duct whereas the other end is tightly closed by a removable cover. The walls of the filter cell are at least partly made of perforated bricks, through which the hot gas entering the filter cell may overflow to a treated gas discharge duct. The filter cell is lined over the whole length thereof with a replaceable filter hose of heat resistant fabric or tissue, preferably non-woven ceramic fiber fabric or a fabric of ytrium-oxide stabilized zircon-oxide fibers.

Abstract: A gas-liquid separator, especially for use with a submersible well pump, having a substantially conical-shaped mesh member in the path of flow of gas-laden liquid. The majority of the liquid flows through the mesh; gas bubbles are trapped by the mesh and are swept by the flow of the liquid to a location where they are removed with a relatively small amount of bleed liquid from the separator Any particulate foreign matter in the gas-laden liquid, is trapped by the mesh and is swept along with the gas bubbles to the gas removal location.

Abstract: An apparatus for removing particulate matter from a gas stream includes a sorbent injector, a charging antenna, and a plurality of granular media filter cells. The gas stream containing the particulate matter is directed through an inlet plenum. The sorbent injector, located within the inlet plenum, injects fine particles of a sorbent material toward the charging antenna for electrostatically charging the sorbent particles. The charged sorbent particles form a large charged surface area for inducing charges on the particulate matter entrained by the gas stream. The plurality of filter cells each include inner and outer perforated, concentric cylinders, and granular media is caused to move downward between the inner and outer cylinders of each filter cell.

Abstract: A reusable filter to remove contaminants from high temperature gases, in excess of 4500.degree. F., developed by burning propellants and used to do work such as actuation of piston-powered devices in aircraft store ejector racks. Contaminants are removed to prevent fouling of the device being acted upon. The filter has a metal strip wound in the form of a helix, the turns of the helix being spaced from one another to permit side entry of the gas between the turns. Protuberances spaced along one side of the strip establish filter gaps between the turns. A closed, convoluted structural support runs through the center of the helix from one end to the other of the filter in order to support the shape of the helix. The convoluted structural support also defines a plurality of axial flow passages between its closed surface and the helix, the passages communicating with the filter gaps to allow axial gas flow along the inside of the filter for end exit.

Abstract: A reusable filter to remove contaminants from high temperature gases, in excess of 4500.degree. F., developed by burning propellants and used to do work such as actuation of piston-powered devices in aircraft store ejector racks. Contaminants are removed to prevent fouling of the device being acted upon. The filter has at least one metal strip wound in the form of a flat spiral about a central member, the turns of the flat spiral being spaced from one another to permit axial entry of gas between the turns. A further flat spiral filter may be similarly constructed about the central member and axially displaced from the first filter, and both such filters may have different filtering capacities. On each flat spiral, protuberances are spaced along one side of the metal strip to establish filter gaps between the turns. The one or more flat spirals are restrained at their outer circumference by a cylindrical casing having inlet and outlet ends for the hot gas.

Abstract: A reusable filter to remove contaminants from high temperature gases, in excess of 4500.degree. F., developed by burning propellants and used to do work such as actuation of pistonpowered devices in aircraft store ejector racks. Contaminants are removed to prevent fouling of the device being acted upon, to increase reliability and to decrease maintenance of the device. The filter has stacked metal discs spaced from one another to permit side entry of the gas between the disc edges, and the discs are made of molybdenum, columbium or tantalum. A plurality of studs pass through the discs to align and hold the filter together, with raised bosses at the stud holes in each disc establishing the filter gaps between the discs. Each disc has a plurality of flow openings communicating with the filter gaps and aligned with the openings of the other discs to allow axial gas flow along the filter for end exit.

Abstract: A low profile chemical biological air filter, comprising a frame having a rst end for attachment to a mask and having an upwardly facing surface defining an inlet for the filter. The frame has a length sufficient to space first and second filters from the inlet to the attachment first end and a width sufficient to enclose the two filters. Its thickness is no greater than that necessary to contain only one of the two filters to minimize the thickness of the frame by placing the two filters side by side. The filters include a HEPA filter for removing particulate material from the air and a Whetlerized charcoal filter bed for secondary filtering of the air. The HEPA filter is supported in the frame at the inlet as is the charcoal filter bed along with a fines filter for protecting from dust which may be dislodged from the charcoal filter bed.