Abstract: An ion generating apparatus is built by sandwiching a dielectric layer between an induction electrode and a discharge electrode. The induction electrode is formed of a metal substrate of, for example, aluminum. Even when the apparatus is made larger, it offers improved mechanical strength compared with a conventional structure employing a dielectric layer formed of a ceramic substrate, a brittle material. The dielectric layer is formed of a thin film having an insulation breakdown withstand voltage of 30 V/?m or more and having a thickness of 30 ?m or less. The discharge electrode is formed on the dielectric layer such that the area occupied by the electrode portion of individual line-shaped electrodes is smaller than the area occupied by the non-electrode portion thereof. This helps to make the discharge voltage lower and to reduce the amount of ozone generated by electric discharge.

Abstract: An oxygen separator for separating oxygen from ambient air utilizing a vacuum swing adsorption process has a mass of less than 2.3 kg. A carrier is mountable on a person to support the oxygen separator for ambulatory use.

Abstract: A particle precipitation device for removing particles entrained in a gas stream includes an array of passages through which a gas stream can be directed relatively freely. The passages are provided between plastics walls adapted to create an electrical field within the array. The plastics walls may have areas of conductive material in contact therewith. High and low electrical potentials alternately applied to isolated areas of the conductive material provide charged sites in the array for collecting particles from the gas stream. Alternatively, the plastics walls may have electret properties.

Abstract: A particle precipitation device for removing particles entrained in a gas stream includes an array of passages (10) through which a gas stream can be directed relatively freely. The passages are provided between plastics walls adapted to create an electrical field within the array. The plastics walls may have areas of conductive material (1, 2) in contact therewith. High and low electrical potentials alternately applied to isolated areas of the conductive material provide charged sites in the array for collecting particles from the gas stream. Alternatively, the plastics walls may have electret properties.

Abstract: The invention relates to a method and device for separating materials in the form of particles and/or drops from a gas flow, in which method the gas flow is directed through a collection chamber the outer walls of which are grounded, and in which high tension is directed to the ion yield tips arranged in the collection chamber, thus providing an ion flow from the ion yield tips towards the collection surfaces, separating the desired materials from the gas flow. It is characteristic of the invention that the collection surfaces conducting electricity are electrically insulated from the outer casings; and that high tension with the opposite sign of direct voltage as the high tension directed to the ion yield tips is directed to the collection surfaces. According to an embodiment of the invention the electrical insulation is made of ABS, and the surface conducting electricity comprises a thin chrome layer arranged on the insulation layer.

Abstract: An air cleaner includes a fan unit (1; 1′) and a filter unit (3) that is entirely replaceable, where the fan unit (1; 1′) and the filter unit (3) are mutually connected by a quick coupling and the filter unit includes a filter and an exterior casing that defines an exterior of the air cleaner when the air cleaner is in an operating position.

Abstract: This invention relates to an apparatus and method to electrostatically charge or neutralize particles conveyed in a pneumatic stream. More particularly the invention is drawn to an apparatus that has at least two longitudinal chambers separated from each other with a plate electrode. Within each chamber is at least one corona charging electrode with multiple discharge points and at least one power level zone. The apparatus divides a single gas stream into a multiple streams where corona discharge polarizes or neutralizes particles with a similar or dissimilar polarity causing coalescing or separation of the particles as they exit the charging chambers.

Abstract: An electret is described that includes a surface modified polymeric article having surface fluorination produced by fluorinating the polymeric article.

Abstract: A self-contained electrostatic air filter assembly having two hinged rectangular frames into which is disposed rectangular polyester/wool filter dielectrics with a conducting charging screen in between. The polyester/wool dielectrics are charged through the conducting screen by a high voltage power supply having a low source resistance. The high voltage supply having a small source resistance is integrated into the air filter assembly and connected electrically to the conducting screen. High voltage is quickly dissipated from the screen and dielectrics when the unit is turned off by a specially designed bleeder resistor. As an air mass is forced through the filter, particulates in the air are removed electrostatically quickly and efficiently by the charged polyester/wool filter material. The air filter assembly has been shown to have a high particulate capacity.

Abstract: A filter apparatus of the present invention includes a filter housing having an inlet and an outlet and a filter device locatable therebetween. The filter device includes a filter medium, an electrically conductive screen or mesh, and a conductor for supplying high voltage power. The conductor abuts the filter medium such that when the conductor is subject to a high voltage, the filter medium is polarized and nothing, apart from air or a support or retention material of dielectric material, is on a side of the filter medium immediately opposite to the conductor and no other charge applying device is located upstream of the conductor.

Abstract: An attractive portable air cleaner effectively purifies air in a room or office for added comfort and a healthier environment. Instead of using expensive custom-made filters, the air cleaner uses regular toilet paper or paper towels for customer convenience and lower customer costs. A quiet blower system circulates air through the air cleaner. Ion emitters are positioned near the intake and collector plates support and charge the paper media.

Abstract: Electrets are disclosed comprising syndiotactic vinyl aromatic polymer, for example syndiotactic polystyrene. These electrets have good charge retention at elevated temperature.

Abstract: The present invention provides a filter medium, which contains an electretized nonwoven web of crimped fibers selected from the group consisting of spunbond filaments and staple fibers, wherein the nonwoven web has a Frazier permeability equal to or greater than about 100 ft.sup.3 /min/ft.sup.2 and a density between about 0.01 g/cm.sup.3 and about 0.095 g/cm.sup.3.

Abstract: A corona-assisted electrostatic filtration apparatus which includes a cathode, an anode filter element, and a means of establishing a nonalternating potential difference between the cathode and the anode which is sufficient to maintain a corona field of ionized gas between the cathode and the anode filter element. The anode filter element includes a porous fibrous sheet material having pores in a range of from about 0.1 to about 100 micrometers, with at least a portion of the fibers thereof being uniformly coated with a metal. Also provided is a method of utilizing such apparatus to remove particulate matter from a gaseous medium.

Abstract: A clog-resistant filter for extracting fine particulate contaminants, such as smoke, from a gaseous fluid stream, such as air, uses interaction between Van der Waals forces and a non-ionizing electrostatic field to efficiently capture the contaminant particles in a filter material whose pores are many times larger than the diameter of the particles to be captured. The filter material is physically so configured to further enhance that interaction and is disposed between at least a pair of electrodes of opposite polarity. The material may be spaced apart from the electrodes, but preferably touches one of them. The particles are trapped generally throughout the thickness of the filter material but ample room is left for continued air flow. The electrostatic voltage is preferably between 3 and 9 kV and is largely independent of electrode spacing. The configuration of the filter material is such that the flow velocity through the material is less than 0.1 m/sec, preferably on the order of 0.03 m/sec.

Abstract: An ionizing type air cleaner having ionizing needle(s) and a collector element. The collector element is made of either many conducting elements with isolating resistors or a single high resistivity element in order to prevent electric shock when touched.

Abstract: A low-profile gas purifying apparatus includes a plurality of conductive plates each having a serrated portion at the periphery thereof. The plates are disposed opposite a flat electrode which is coated with a dielectric layer and are separated from the flat electrode by a predetermined gap. A high voltage A.C. power source is connected between the plates and the flat electrode. The plane surfaces of the conductive plates are slanted with respect to the gas flow direction to reduce flow resistance through the apparatus.

Abstract: The invention relates to apparatus for biological purification and filtration of air. The apparatus includes a coarse filter (1), an ionizer (5), an additional plate (9) and a fine filter (10), which are installed in this order along the path of the gas flow, and a power source (23). The coarse filter (1) is essentially an electrostatic precipitator consisting of three plates (2,3,4) adjacent to each other, the outer-most (2,3) of which are made of a cellular metal and are connected electrically to the opposite-in-sign terminals of the power source (23), whereas the central plate (4) is made of polyurethane foam. The coarse filter (1) abuts closely on the cylindrical nondischarge electrode (6) of the ionizer (5).

Abstract: An electrostatic air cleaner is disclosed for use in removing particulate matter from moving streams of air. A high voltage ionizer is used as a corona source to ionize the particulate matter as it approaches the air filter portion of the electrostatic air cleaner. The air filter uses reticulated polyether foam filter media for collecting the particulate matter, and the filter media is non-deliquescent, thus preventing the high-voltage electric field from being dissipated by imbedded water vapor, which is the cause of filter inefficiency in the prior art. In one embodiment, the air filter uses strips of conductive material raised to a very high DC voltage interleaved between strips of conductive material held to ground potential, and these strips are oriented so as to be parallel to the direction of the air flow through the air filter's foam filter media, thereby creating an electric field that is perpendicular to the direction of air flow.

Abstract: An electret filter formed by laminating a plurality of network electret film-split fiber fleeces having a different mesh size. It exhibits a high collecting efficiency with a very small pressure loss and without any appreciable fiber dropping, or any channeling.

Abstract: The improved nonwoven fabric in an electret state is composed of monofilaments with an average fiber diameter of 0.5-100 .mu.m that are formed of a polymer composition containing no more than 1 mol % of polar groups; the fabric has a weight of 5-100 g/m.sup.2, a bulk density of 0.05-0.40 g/cm.sup.3 and an average surface charge density of at least 0.1.times.10.sup.-9 C/cm.sup.2. This nonwoven fabric is capable of efficient dust collection and its trapping ability is retained for a prolonged time even in a hot and humid condition. Also disclosed are a process for producing this nonwoven fabric, as well as a filtering and an air masking material which are composed of that nonwoven fabric.

Abstract: An electrostatically stimulated air filter and process, contemplates a housing having an fluid intake and a fluid exhaust; a upstream electrode, disposed downstream of the fluid intake, for carrying a ground potential; a filter, disposed downstream of the prefilter, for filtering out contaminants in the fluid; an ionizing electrode, disposed between the filter and the prefilter, for carrying a second potential; and a downstream electrode, disposed downstream of the filter, for carrying a ground potential; and a fan, downstream of the filter, for driving air through the prefilter and the filter. Ionization of incoming fluid occurs as a result of electric fields generated by the downstream electrode, the ionizing electrode, and the upstream electrode. The filter comprises an upstream dielectric layer and a downstream conductive layer, usually fibers coated with activated carbon powder.

Abstract: A non-ionizing, clog-resistant filter for extracting fine particulate contaminants such as smoke from a gaseous fluid stream such as air uses interaction between Van der Waals forces and a non-ionizing electrostatic field to efficiently capture the contaminant particles in a filter material whose pores are many times larger than the diameter of the particles to be captured. The filter material is physically so configured to further enhance that interaction, and is disposed between at least a pair of electrodes of opposite polarity. The material may be spaced from the electrodes, but preferably touches one of them. The particles are trapped deeply into the thickness of the filter material and leave ample room for continued air flow. The electrostatic voltage is preferably between 3 and 9 kV and is largely independent or electrode spacing. The configuration of the filter material is such that the flow velocity through the material is less than 0.1 m/sec, preferably on the order of 0.03 m/sec.

Abstract: An electrostatic air cleaner is disclosed along with a method for removing particulate matter from moving streams of air. A high voltage ionizer is used as a corona source to ionize the particulate matter as it approaches the air filter portion of the electrostatic air cleaner. The air filter uses a pair of reticulated polyether foam filters for collecting the particulate matter. The foam filters are separated by a thin, grid-like layer of semiconductive material (carbon-impregnated polycarbonate) which is raised to a very high DC voltage. The foam filters are also surrounded by thin, grid-like layers of electrically conductive material which are held at ground potential, thus creating a high-voltage electric field through each of the foam filters. The polyether foam filter media is non-deliquescent, thus preventing the high-voltage electric field from being dissipated by such imbedded water vapor, which is the cause of filter inefficiency in the prior art.

Abstract: A first recess for detachably mounting an ionizer therethrough is formed to oppose a dust-collecting air suction side of a precipitator machine body. The ionizer includes an ionizing wire unit having an ionizing wire, and a counterelectrode plate, which can be detachably assembled. A second recess for detachably mounting a dust collector therethrough is formed to oppose a dust-collecting air discharge side of the precipitator body. The dust collector captures and collects dust particles, charged by the ionizer, with a Coulomb force. The ionizer and dust collector are simultaneously electrically connected to the body when they are mounted on the corresponding recesses.

Abstract: Non-diffusible dye-providing compounds for the dye diffusion transfer process yielding color images of wanted absorption characteristics and improved light fastness correspond to the formula(A).sub.n -P-N=N-B-(A).sub.1-nin whichA represents an oxidizable organic carrier residue which may be attached through a connecting member X and containing a group which confers diffusion resistance, from which carrier residue, either in its oxidized or in its unoxidized form, a part is split off together with the group which confers diffusion resistance under alkaline photographic development conditions, a diffusible azo dye represented by the formula P--N.dbd.N--B being released imagewise at the same time;P represents a monocyclic, carbocyclic aromatic group;B represents a bicyclic, carbocyclic aromatic group which carries a sulphonamide group in the p-position to the azo group;N=0 or 1.

Abstract: A photographic element comprising a support, a layer containing certain photographically useful fragments and a layer containing a dye mordant composition comprising a polymer having recurring units of the formula: ##STR1## wherein: A comprises polymerized units of ethylenically unsaturated monomers;R is H or alkyl;R.sup.1 is H, alkyl or is a group containing at least one atomatic nucleus;Q is a linking group;Y is H or an inert group;X is a leaving group;E and F are the atoms necesary to complete a 5-7 membered heterocyclic ring;N is 0 to 2;M is 1 to 3;P is 0 or 1;X is 0 to 90 weight percent; andY is 10 to 100 weight percent of the polymer.The polymeric mordants covalently bond with dyes or dye precursors and are especially useful in diffusion transfer processes.

Abstract: Novel yellow ortho, ortho' dihydroxy azomethine dyes and metal complexes of such dyes which are particularly useful in photographic products and processes are presented by this invention. The novel yellow ortho, ortho' dihydroxy azomethine dyes have the following structural formula: ##STR1## WHERE N' IS THE INTEGER 1-8 AND M' IS THE INTEGER 1 OR 2.

Abstract: A color photographic material having on a support at least a photographic emulsion containing an excellent colored coupler represented by the general formula ##STR1## wherein R.sub.1 represents an aryl group or a heterocyclic group; R.sub.2 represents a phenyl group having a halogen atom, an alkoxy group, or an aryloxy group at the ortho-position to the imino group bonded to the 3-position of the pyrazolone ring of the coupler; and R.sub.3 represents a phenyl group having a hydroxyl group at the para-position to the azo group of the coupler; the coupler having a hydrophobic diffusion-resisting group in the molecule thereof.

Abstract: Suitable masking compounds for masking the undesired color side densities of image dyes produced from color couplers are those of the following formula ##STR1## in which R.sup.1 represents hydrogen or one or more substituents such as halogen, alkyl, aryl, a heterocyclic group alkoxy, hydroxyl, amino, acylamino, sulfo, sulfonyl, carboxyl or carbamyl or condensed carbocyclic or heterocyclic ring.R.sup.2 represents alkyl, aryl, a heterocyclic group carboxyl or esters or amide derived from carboxylX represents a dye group optionally containing a solubilizing group.On development with black-and-white or color-forming developers the dye group is released imagewise and is removed by aqueous processing baths leaving back a positive color or masking image.

Abstract: Photographic elements, diffusion transfer assemblages and processes are described which employ a novel nondiffusible compound having a novel releasable azo dye. The dyes are azophenols, or precursors of azophenols, and have electron withdrawing groups in each of the positions ortho to the phenolic hydroxy group.

Abstract: The present invention relates to novel bicyclic compounds useful as photographic silver halide developing agents, to the preparation of these compounds and to photographic products, processes and compositions employing the same. The subject compounds may be represented by the formula ##STR1## wherein R.sub.1 and R.sub.2, the same or different, each represents hydrogen, a hydrocarbon moiety, preferably an alkyl group, --COOH or --COOR.sup.1 wherein R.sup.1 is an alkyl group; R.sub.3 and R.sub.4, the same or different, each represent hydrogen or an alkyl group, R.sub.5 represents hydrogen or --COR.sup.2 wherein R.sup.2 is an alkyl group; R.sub.6 represents hydrogen when R.sub.5 is hydrogen and represents hydrogen or --OCOR.sup.3 wherein R.sup.3 is an alkyl group the same as R.sup.2 when R.sub.5 represents --COR.sup.2 ; X represents --OH, --NH.sub.2 or --NHCOR.sup.4 wherein R.sup.4 represents an alkyl group the same as R.sup.2 ; Y represents --OH or --OCOR.sup.5 wherein R.sup.

Abstract: A dye-releasing mechanism is described which employs a nondiffusible dye-releasing compound having a dye or dye-precursor moiety attached thereto through a sulfonamido cleavage linkage so that a diffusible sulfonamide dye or dye-precursor will be released upon oxidation and subsequent alkaline hydrolysis of the compound.

Abstract: Photographic elements, diffusion transfer assemblages and processes are described which employ a novel nondiffusible compound having a releasable pyridylazopyrazole or pyrimidylazopyrazole dye moiety. The compound contains in the ortho position of the azopyrazole moiety a metal chelating group, a salt thereof or a hydrolyzable precursor thereof, and a ballasted carrier moiety which is capable of releasing the diffusible azo dye under alkaline conditions. The dye is transferred imagewise to an image-receiving layer where it is contacted with metal ions to form a metal-complexed azo dye transfer image of excellent stability.

Abstract: Photographic elements, diffusion transfer assemblages and processes are described which employ a novel nondiffusible compound having a releasable azo dye moiety. The compound has the formula: ##STR1## wherein: G is a metal chelating group (or a salt or hydrolyzable precursor thereof) or a group which together with a ##STR2## IS CAR (bonded through the oxygen); G.sup.1 is a hydroxy group (or a salt of hydrolyzable precursor thereof);Z is an electron withdrawing group;Z' is alkyl, aryl or N(R).sub.2 (R being H, alkyl or aryl);Car is a ballasted carrier moiety; andT is 0 or 1.The dye can be transferred imagewise to an image-receiving layer where it can be contacted with metal ions to form a metal-complexed azo dye transfer image of excellent stability. The retained dye image in the photographic element can also be bleached, fixed and metallized to form a color transparency or a motion picture film.

Abstract: Photographic elements, diffusion transfer assemblages and processes are described which employ a novel nondiffusible compound having a releasable 1-arylazo-4-isoquinolinol dye moiety. The compound contains:(a) in the ortho position of the arylazo moiety a metal chelating group, a salt thereof or a hydrolyzable precursor thereof; and(b) a ballasted carrier moiety which is capable of releasing the diffusible azo dye under alkaline conditions. The dye is transferred imagewise to an image-receiving layer where it is contacted with metal ions to form a metal-complexed azo dye transfer image of excellent stability.

Abstract: Photographic elements, diffusion transfer assemblages and processes are described which employ a novel nondiffusible compound having a releasable 2-(5-nitro-2-pyridylazo)-1-naphthol dye moiety. The compound contains a ballasted carrier moiety which is capable of releasing the diffusible azo dye under alkaline conditions. The dye is transferred imagewise to an image-receiving layer where it is contacted with metal ions to form a metal-complexed azo dye transfer image of excellent stability.

Abstract: Photographic elements, diffusion transfer assemblages and processes are described which employ a novel nondiffusible compound having a releasable azo dye moiety such as an arylazo-pyrazolotriazole or arylazo-pyridinol. The compound contains:(a) a nitrogen atom in a metal chelating location in at least one of the rings attached to the azo group;(b) in the ortho position of the arylazo moiety a metal chelating group (or a salt thereof or a hydrolyzable precursor thereof), and(c) a ballasted carrier moiety which is capable of releasing the diffusible azo dye under alkaline conditions.The dye is transferred imagewise to an image-receiving layer where it is contacted with metal ions to form a metal-complexed azo dye transfer image of excellent stability.

Abstract: Aromatic nitro compounds are disclosed where the aromatic ring contains electron-withdrawing groups and said aromatic nitro compound is capable of undergoing intramolecular nucleophilic displacement after reduction of the nitro group. The compounds are especially useful in photographic elements where an image dye-providing material or a photographic reagent are released upon cleavage from the compound.

Abstract: Non-diffusible dye-providing compounds for the dye diffusion transfer process yielding yellow to red color images of wanted absorption characteristics and improved light fastness correspond to the formula(A.sup.1).sub.n -- D -- N .dbd. N -- Py -- (A.sup.1).sub.1-nin whichA.sup.1 represents an oxidizable organic carrier residue which may be attached through a connecting member X and containing a group which confers diffusion resistance, from which carrier residue, either in its oxidized or in its unoxidized form, a part is split off together with the group which confers diffusion resistance under alkaline photographic development conditions, a diffusible azo dye represented by the formula P--N.dbd.N--B being released imagewise at the same time;D represents a heterocyclic or carbocyclic aromatic group;Py represents a pyridine or 1,2-dihydropyridine group which is attached to the azo group through its 3-position and carries an amino or hydroxyl group in its 6-position;N = 0 or 1.

Abstract: Positive images including color images are obtained by imagewise exposure and development of a material which comprises at least one light-sensitive silver halide emulsion layer which contains an unfogged direct-positive silver halide emulsion, when the development is carried out in the presence of a fogging agent of the formula ##STR1## wherein the symbols are defined as hereinafter. The fogging agent is preferably contained in a layer of the material and more preferably in the unfogged direct-positive silver halide emulsion layer. For the production of color instant images the material may also contain non-diffusible color providing compounds capable in their oxidized form of being split under alkaline photographic development conditions to release diffusible dyes.

Abstract: Photographic elements, processes for forming images in photographic elements and new compounds are disclosed. Generally, the invention relates to ballasted electron-accepting nucleophilic displacement compounds; after acceptance of at least one electron (reduction) by a nucleophile precursor group, the compounds are capable of undergoing intramolecular nucleophilic displacement to release a diffusible moiety, such as an image dye or a photographic reagent. In certain embodiments, the ballasted electron-accepting nucleophilic displacement compounds are used in combination with electron donors and electron-transfer agents. The processes disclosed are particularly useful in providing positive transfer images using negative-working silver halide emulsions.

Abstract: A novel class of redox releasing compounds contains an N,N-disubstituted carbamoyl ballast group. These compounds can be used in photographic elements and processes to release a dye or other photographically useful group as a function of silver halide development.

Abstract: Polymeric derivatives of tetrazole-5-thiols are useful in conjunction with photosensitive silver halide elements as interlayers to provide interimage control, as dispersants for dye image-forming materials or as silver scavengers.

Abstract: A method for adding oil-soluble photographic addenda in the form of their solution in a high boiling organic solvent to a hydrophilic colloidal solution for forming a layer of a light-sensitive silver halide photographic material in the homogeneously dispersed state, is described.

Abstract: Photographic dye developing agents represented by the following formula (I): ##STR1## wherein A represents an anthraquinone dye moiety, X represents a hydrogen atom, an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aryl group or a heterocyclic group, at least one of A and X contains an o-dihydroxyphenyl group or a p-dihydroxyphenyl group as a dye developing agent moiety, n is an integer of 1 to 4, and COY represents a group which is released from the nitrogen atom at a pH of above 9.

Abstract: A color photographic light-sensitive material comprising a support having thereon at least one layer of a silver halide photographic emulsion with the light-sensitive material containing at least one hydroquinone compound represented by the following general formula (I): ##STR1## wherein R.sup.1 represents a hydrogen atom, ##STR2## or a precursor thereof.

Abstract: The invention is directed essentially to photographic material containing, on a carrier, a layer with azo dyestuffs of the formula ##STR1## wherein A, B, X and Y are certain substituents, in a second main aspect azo dyestuffs of the formula ##STR2## wherein B' represents certain substituents and in a third main aspect azo deystuffs of the formulaA.sub.1 --N.dbd.N--B.sub.1 --NH--CO--X.sub.1 --Y--Z.sub.1 --OC--HN--B.sub.1 --N.dbd.N--A.sub.1wherein A.sub.1, B.sub.1, X.sub.1, Z.sub.1 and Y are certain substituents.The photographic materials provide advantages stemming from the use of the dyestuffs of the invention which are distinguished by particularly high fastness to light coupled with excellent bleachability, good resistance to diffusion and advantageous color strength.

Abstract: In the photographic dye-diffusion transfer process use is made of dye-giving compounds, which are non diffusing in photographic binder layers, and which during development if oxidized imagewise in accordance with the silver halide developed are split owing to the alkali of the developer composition to release diffusing dyes, which are transferred to an image-receiving layer. The dye-giving compounds have the formulaY--NH--Ar--NH--SO.sub.2 --Xar represents an arylene radical such that the group Y--NH-- is attached to the group --NH--SO.sub.2 --X through a chain of n(n=1,2,3, or 4) vinylene groups which are part of the arylene radical;X represents the radical of a dye or dye precursor;Y represents a --COR or --SO.sub.2 R radical; andR represents an alkyl, aryl or heterocyclic group and can constitute part of a second dye moiety.

Abstract: An adjustable air filter for use in heating, ventilating, cooling, and forced air systems. The air filter includes a media for filtering air and adapted to be cut with scissors, and a frame embracing the peripheral edges of the media. The frame includes a pair of male sections and a pair of female sections respectively telescopingly receiving the male sections. Also, the frame is adapted to be cut with scissors and is preferably formed of polyvinyl chloride. Each of the male sections includes a T-shaped projection and each of the female sections includes a complementary shaped T-shaped slot adapted to telescopingly receive the T-shaped projection for preventing inward separation of the sections from one another. In the preferred form the media is of the electrostatic type and includes at least one layer of polypropylene woven in an egg-crate pattern. Also, the layer preferably includes a pad of washable polyester material.