JP6192057B2 - Air purification filter - Google Patents

Description

  The present invention relates to a filter used by being incorporated in an air purification device, and more particularly to an air purification filter suitable for purification of air containing substances harmful to the human body such as formalin.

  In anatomical practice at medical and dental departments, in order to prevent corruption and bacterial growth, formalin is injected and autopsy specimens immersed in ethanol are dissected on the dissection table. In order to prevent the harmful substances from being diffused into the dissection room, the air around the dissection table is taken into the air purification device, and the harmful substances are removed and cleaned, and then released into the dissection room.

  For example, as described in Patent Document 1, the air purification apparatus incorporates a filter in an air flow path inside a filter chamber (filter housing), and sucks external air into the filter chamber by a blower. A filter having a structure in which harmful substances contained in the air are decomposed and removed by passing a filter medium in the filter is used.

  FIG. 9 is a partial cross-sectional view in the horizontal plane showing the main structure inside the filter chamber of such an air purifier, and an intake air for taking in external air to one end of the filter chamber A1 shown in FIG. A mouth A2 is provided. Although not shown, an exhaust port communicating with a blower built in the air purifier is provided at the other end of the filter chamber A1.

  As shown in the figure, a plurality of air purification filters A3 are incorporated in an air flow path formed inside the filter chamber A1. In these air purification filters A3, as shown in FIG. 10, a filter medium F made of granular potassium permanganate is filled inside a box-like filter casing A4 that is flat in the ventilation direction.

  A perforated plate A5 is mounted on the front and rear surfaces of the filter casing A4 in the ventilation direction so that air can pass in the front-rear direction. (In the following description, the front surface means the air flow inflow side surface, and the rear surface means the outflow side surface.)

  The upper surface of the filter casing A4 is provided with an opening A7 that is sealed by the lid A6. The filter casing A4 is filled with the filter material F from the opening A7, or a new used one is added. It can be refilled. Further, a seal member S made of a belt-like rubber material is attached to the rear peripheral edge portion of the filter casing A4 over the entire circumference.

  As shown in FIG. 9, in the air purification filter A3 configured as described above, each filter casing A4 is held by a filter holding member A8 fixed in the filter chamber A1.

  The rear surface of the peripheral edge of the filter casing A4 of the air purification filter A3 arranged on the most downstream side in the ventilation direction is the filter positioning member A9 attached over the entire inner wall of the filter chamber A1 via the seal member S. It is in contact with the front end face.

  Further, a pressing member of a filter fixing mechanism (not shown) is pressed against the front peripheral edge of the filter casing A4 of the air purification filter A3 disposed on the most upstream side, and these air purification filters A3 are It is sandwiched between the pressing member and the filter positioning member A9 and fixed at a predetermined position in the filter chamber A1.

  Note that the gap between the filter casings A4 adjacent to each other in the front and rear direction and the gap between the most downstream filter casing A4 and the front end face of the filter positioning member A9 are sealed by the seal member S, respectively.

JP 2013-654 A

  By the way, when air passes through the filter A3 having the conventional structure as described above, the portion surrounded by the one-dot chain line circle a of the filter casing A4 in FIG. 9 is an enlarged view of this portion as shown in FIG. The resistance received when the air X passing through the perforated plate A5 and flowing into the filter casing A4 passes between the particles of the filter medium F and the smooth side wall inner surface of the filter casing A4 is between the particles of the filter medium F. The amount of air X is less than the resistance that is received when passing through the filter, so that a large amount of air X flows through the gap between the inner wall of the filter casing A4 and the filter medium F, passes through the filter A3, and is harmful in the air X due to contact with the filter medium F. There is a problem that the substance is discharged from the air purifier into the room without being sufficiently decomposed and removed.

  In particular, as shown in FIG. 9, in the case where the filter A3 has a structure that allows ventilation from the horizontal direction, even if the filter medium A is initially filled with the filter medium F, Due to the influence of external vibration, the overall volume decreases with time, and the gap between the filter medium F and the top plate A6 (see FIG. 10) of the filter casing A4 gradually increases. There was a problem that the air purification function of A3 rapidly deteriorated.

  In addition, the filter medium F adjacent to the inner surface of the side wall of the filter casing A4 is locally exposed to a large amount of air having a large flow velocity, so that harmful substances are decomposed and removed as compared with the filter medium F in other parts. There was also a problem that the ability deteriorated early.

  By the way, when potassium permanganate is used for the filter medium, the color of the filter medium inside the filter casing is upstream of the ventilation direction in the process of oxidizing and decomposing harmful substances such as formalin contained in the air. From the thing toward the downstream side, the color gradually changes from reddish purple to brown according to the degree of deterioration.

  Therefore, an attempt has been made to determine a filter replacement time by forming a part of the side wall of the filter chamber or the filter casing with a transparent material such as glass and visually confirming the color change state of the filter medium from the outside of the filter chamber.

  However, as described above, if only the filter medium adjacent to the inner surface of the transparent material part of the filter casing is locally deteriorated at an early stage, there is a problem that it is difficult to appropriately determine the filter replacement time. It was.

  Further, in the portion where the perforated plate A5 surrounded by the dot-dash line circle b in FIG. 9 and the filter medium F are adjacent, as shown in FIG. 12 which is an enlarged view of this portion, the perforated plate A5 on the inflow side of the air X The particles of the filter medium F located directly behind the vent hole h (grains shown by hatching in the figure) and the filter medium F in contact with the back surface of the perforated plate A5 at a position away from the vent hole h. Since there is a difference in the flow rate of air striking the surface of these grains, there is a problem in that the degree of deterioration varies.

  Therefore, the present invention eliminates the problems in the prior art as described above, can enhance the effect of removing harmful substances, and can prevent local early deterioration of the filter medium in the filter casing. The purpose is to provide a filter.

The air purification filter of the present invention provided for the above-mentioned purpose is filled with a granular filter medium inside a frame-shaped or cylindrical filter casing, whose end surfaces before and after the aeration direction are each composed of a porous plate, An air purification filter that is used by being incorporated in a filter chamber of an air purification device, wherein the filter casing is configured to cause an air flow that is in contact with an inner surface of the side wall and passes through the inside of the filter casing to flow at least on the inner surface of the side wall. A wall surface flow blocking member that is partially blocked from the inner surface of the side wall and detoured so as to increase the path length in contact with the filter medium is provided so as to protrude from the inner surface of the side wall into the filter medium.

In addition, an oxidizing agent whose surface color changes according to the degree of progress of deterioration is used for the filter medium, and at least a part of the side wall of the filter casing has an outer color change state of the filter medium along the ventilation direction. A transparent material that is visible from the inside, and the inner surface of the transparent material has a square shape in which the longitudinal direction is substantially perpendicular to the ventilation direction and the length of one side is substantially equal to the average particle diameter of the filter medium A cross-shaped wall-shaped flow blocking member having a transverse cross section is provided .

In the air purification filter, the filter casing is installed in the filter chamber in such a direction as to vent downward from above, and between the upper surface of the filter medium filled therein and the lower surface of the upper porous plate facing the filter medium. In addition, it is desirable that air gaps are provided for diffusing the air flow that has passed through the air holes of the perforated plate substantially uniformly over the upper surface of the filter medium .

  According to the air purification filter of the first aspect of the present invention, the wall surface flow blocking member causes an air flow that passes through the inside of the filter casing in contact with the inner surface of the side wall to pass through the inner surface of the side wall at least at a part of the inner surface of the side wall. In order to prevent the air from passing through the filter casing and to make a detour so as to increase the path length in contact with the filter medium, a part of the air taken into the filter casing does not pass through the inner wall of the side wall as it is, and by sufficient contact with the filter medium Effectively removes harmful substances.

  Moreover, since the flow rate of the air flowing on the inner side of the side wall of the filter casing is limited by the provision of the wall surface flow blocking member, it is possible to prevent local early deterioration of the filter medium in the vicinity of the inner side of the side wall of the filter casing. As a result, it is possible to extend the filter replacement interval or the filter material refill interval.

In addition, it is possible to easily grasp the timing of filter replacement by visually checking the degree of deterioration of the filter medium along the ventilation direction from the outside of the side wall of the filter casing made of a transparent material. Can do .

At that time, a cross-shaped wall-shaped flow blocking member having a square cross section in which the length of one side is substantially equal to the average particle diameter of the filter medium, the longitudinal direction being substantially perpendicular to the ventilation direction, is formed on the inner surface of the transparent material. Because it increases the contact area with the filter medium and increases the ventilation resistance of the air flow that bypasses this part, the flow rate of air passing through the gap between the inner surface of the transparent material and the filter medium adjacent thereto can be suppressed. .

As a result, it is possible to avoid the problem that only the filter medium in contact with the transparent material inner surface visible from the outside is exposed to a large amount of air flow and deteriorates or discolors at an early stage, thereby preventing erroneous judgment of the filter replacement time. Can

According to the air purification filter according to the second aspect of the present invention, in addition to the effect brought about by the first aspect of the invention described above, the upper surface of the filter medium filled in the filter casing and the upper side opposite thereto are further provided. Between the lower surface of the perforated plate is provided with a gap for decelerating the high-speed air flow that has passed through each vent hole of the perforated plate and diffusing substantially uniformly over the entire upper surface of the filter medium, Air can be permeated uniformly throughout the filter medium .

As a result, it is possible to further enhance the effect of removing harmful substances contained in the air and to prevent partial early deterioration of the filter medium. Can be extended .

It is a longitudinal cross-sectional view of the filter chamber of the air purification apparatus incorporating the air purification filter of the present invention. It is a disassembled perspective view of the filter casing in one Embodiment of the filter for air purification of this invention. It is a fragmentary sectional view inside a filter casing in one embodiment of a filter for air purification of the present invention. It is a figure which shows typically the ventilation path | route of the wall surface flow-blocking member vicinity in one Embodiment of the filter for air purification of this invention. It is a fragmentary sectional view of the window part vicinity of the filter casing in one Embodiment of the filter for air purification of this invention. It is a figure which shows typically the flow velocity distribution of the airflow which passes through the inside of the space | gap of filter casing upper part in one Embodiment of the filter for air purification of this invention. It is a fragmentary sectional view inside the filter casing in another embodiment of the filter for air purification of the present invention. FIG. 8 is an enlarged view of a portion surrounded by a dashed line A in FIG. It is a fragmentary sectional view in the horizontal surface which shows the principal part structure inside the filter chamber of the conventional air purification apparatus. It is a disassembled perspective view of the conventional air purification filter. FIG. 10 is an enlarged view of a portion surrounded by a dashed line a in FIG. 9. FIG. 10 is an enlarged view of a portion surrounded by a dashed line b in FIG. 9.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal sectional view of a filter chamber incorporating an air purification filter of the present invention (hereinafter also simply referred to as a filter). As shown in FIG. 1, the filter 1 of the present invention has a box shape. Are arranged side by side in two upper and lower stages in an air passage formed in the vertical direction inside the filter chamber 2.

  The filter chamber 2 is a part of an air purification device not shown in its entirety, and an intake port 3 for taking in external air containing harmful substances such as formalin mist is provided at the upper end thereof. An exhaust port 4 is provided at the lower end.

  The exhaust port 4 communicates with a blower (not shown), and the air in the filter chamber 2 is sucked out from the exhaust port 4 and exhausted by the blower, so that air is introduced from the intake port 3 into the filter chamber 2. It comes to be taken in.

  In the filter chamber 2, there is provided a wind guide plate 5 whose upper surface is slightly inclined at a medium and high height for guiding the air flow taken in from the intake port 3 to expand radially, and below the filter chamber 2. A horizontal perforated plate 6 is provided that rectifies so that the air flow velocity is substantially uniform over the entire cross section of the air flow path in 2.

  In addition, the two filters 1 have the same specification, in which a granular filter medium F of potassium permanganate is filled in a box-shaped filter casing 7 whose upper and lower end faces are closed by perforated plates. belongs to.

  As shown in FIG. 2, the filter casing 7 of these filters 1 is composed of a rectangular parallelepiped casing body 8 and a casing lid body 9 that closes the upper end thereof, and a bottom plate 8 </ b> A of the casing body 8 and the casing lid body 9. Each of the top plates 9A is composed of a perforated plate.

  In the present embodiment, a stainless steel porous plate having an inner diameter of the air hole h of 3 mm is used for these porous plates, and the filter medium F filled in the filter casing 7 is used. In this case, the surface of granular (pellet-shaped) alumina having an average particle diameter of about 5 mm is added with potassium permanganate.

  A seal member 10 for sealing a gap between the casing body 8 and the lower surface of the peripheral edge of the casing lid 9 is adhered to the upper surface of the peripheral edge of the casing body 8 over the entire periphery. Further, the casing lid body 9 has a peripheral edge of the casing main body 8 by countersunk screws 11 penetrating the sealing member 10 at a total of six places, four places near the four corners and two places on the left and right sides of the middle position in the longitudinal direction. It is designed to be fixed to the upper surface of the part.

  In addition, a rectangular window portion 13 to which a transparent glass plate 12 (transparent material) is attached from the inside is provided on the front side wall 8 a of the casing body 8. As shown in FIG. 1, the window portion 13 is formed on the front surface (right surface in FIG. 1) of the filter chamber 2 in a state where the two filters 1 are incorporated in the filter chamber 2. Facing the replacement opening 14.

  The filter replacement opening 14 is normally sealed with a removable lid 15. The lid 15 is provided with an observation window 15A on which transparent glass is mounted, and the filter medium F in the upper and lower filters 1 can be visually recognized from the outside of the filter chamber 2 through the observation window 15A. It has become.

  Further, inside the filter chamber 2, a receiving member 16 having a rectangular frame shape in plan view that supports the entire periphery of the bottom peripheral edge of the casing body 8 of the lower filter 1, and the front and rear directions and the left and right directions of the two upper and lower filters 1. A positioning member 17 having a U-shape in plan view for positioning the position is provided.

  In addition, a band-shaped seal member 18 made of a rubber material is attached to the entire periphery of the bottom surface of the casing body 8 of each filter 1, and the lower filter 1 is formed by these seal members 18. Between the bottom peripheral edge of the casing body 8 and the top surface of the receiving member 16, and between the bottom peripheral edge of the casing main body 8 of the upper filter 1 and the upper peripheral edge of the casing lid 9 of the lower filter 1, respectively. It is sealed.

  When the used filter 1 in the filter casing 2 is replaced with a new one, the cover 15 is removed from the filter chamber 2, the filter replacement opening 14 is opened, and the filter 1 is moved horizontally from here. Take it in and out.

  As shown in FIG. 2, the inner surface of each of the rear side wall 8b, the left side wall 8c, and the right side wall 8d of the casing body 8 has a transverse section so that the longitudinal direction is horizontal and parallel to the upper and lower stages. A rectangular wall surface flow blocking member 19 is bonded and fixed.

  In the present embodiment, these wall flow blocking members 19 are made of an elastic polyurethane foam resin, and are buried in the filter medium F in the filter casing 7 as shown in FIG. In the position.

  As shown in FIG. 4, when the air flow X enters the gap between the inner wall of the filter casing 7 and the filter medium F from above in the ventilation direction, these wall surface flow blocking members 19 block the path of the filter medium F. Guide you to get around.

  As a result, the length of the path through which the air flow X passes through the filter casing 7 and the contact area with the particle surface of the filter medium F are increased as compared with the case where the wall surface flow blocking member 19 is not provided. The removal effect can be enhanced.

  In particular, the wall surface flow blocking member 19 formed of the polyurethane foam resin in this embodiment has a concave surface due to the pressure received from the particles of the surrounding filter medium F, and the contact area with the particles of the filter medium F is small. To increase.

  As a result, since the flow resistance between the wall surface flow blocking member 19 and the filter medium F increases, the air flow X passes between the particles of the inner filter medium F having a smaller flow resistance. As compared with the case where a hard resin or metal material is used, the harmful substances can be decomposed and removed more effectively.

  The polyurethane foam resin has some air permeability because it contains many continuous fine cavities inside, but the internal cavities are crushed when compressed under pressure from the surrounding filter medium F. The air permeability is reduced to such an extent that there is no practical problem.

On the other hand, the glass plate 12 provided in the window part 13 of the casing main body 8 mentioned above is being fixed to the circumference | surroundings of the window part 13 from the inner side by the fixing member 20, as shown in detail in FIG.
A seal member 21 made of a rubber material is incorporated between the inner surface around the window portion 13 and the outer peripheral edge portion of the glass plate 12 so that the air inside does not leak outside.

  As shown in FIGS. 2 and 5, two elongated wall flow blocking members 22 are attached to the inner surface of the glass plate 12 in parallel in the form of a rail in two upper and lower stages with the longitudinal direction set horizontally. It has been. The cross-sectional shape of the wall surface flow blocking member 22 is a square shape whose one side is approximately equal to the average particle diameter of the filter medium F, and one side surface corresponding to the one side is fixed to the inner surface of the glass plate 12. Has been. (In FIG. 5, the size of the wall surface flow blocking member 22 is drawn larger than the particle size of the filter medium F for the sake of clarity.)

  The wall surface flow blocking member 22 diverts the flow of air passing between the inner surface of the glass plate 12 and the filter medium F adjacent thereto into the filter medium F, similarly to the wall flow block member 19 described above, In the filter casing 7, the length of the path in which the air flow contacts with the filtering material F is increased to increase the effect of removing harmful substances contained in the air.

  In the present embodiment, these wall surface flow blocking members 22 are transparent vinyl chloride square bars having a side of a cross section of approximately 5 mm in order to increase the visibility of the filter medium F from the outside of the glass plate 12. It is possible to visually recognize the discoloration state of the particles of the filter medium F located on the back side of the wall surface flow blocking member 22 by using an adhesive that is made of a material and adhesively fixed to the inner surface of the glass plate 12 using an adhesive that solidifies in a transparent state I am doing so.

  The reason why the length of one side of the cross section of the wall flow blocking member 22 is a square shape substantially equal to the average particle diameter of the filter medium F is that if the length of the side perpendicular to the ventilation direction is longer than this, However, since the air flow hardly enters the corners of the inner surface of the glass plate 12 and the wall surface flow blocking member 22, the filter medium F in this portion cannot contribute to the decomposition of harmful substances. On the other hand, when the length of the side in the ventilation direction is increased, the visibility of the filter medium F from the outside of the glass plate 12 is deteriorated.

  Moreover, as shown in FIG. 1, in the thing of this embodiment, the upper surface of the filter medium F with which the inside of the filter casing 7 of each filter 1 was filled, and the top plate 9A (upper perforated plate) facing this are shown. Between the lower surface, gaps R for diffusing the air flow that has passed through the air holes h of the perforated plate substantially uniformly over the entire upper surface of the filter medium F are formed.

  In these gaps R, the airflow that has flowed into the vent holes h of the top plate 9A from above, as schematically shown by the downward arrows in FIG. Only the vicinity of the pores h is locally high speed. (Here, the length of each downward arrow schematically represents the magnitude of the flow velocity at each location in the gap R.)

  However, as the air moves away from the top plate 9A, the air in the portion where the flow velocity is fast drags the surrounding air due to viscosity, so the variation in the flow velocity of the air flow in the same horizontal plane is gradually averaged, and the upper surface of the filter medium F In the vicinity, the speed of the air flow is generally uniform throughout.

  Therefore, as compared with the case where the filter casing 7 is fully filled up to the position where the upper surface of the filter medium F is in contact with the top plate 9A, the entire upper filter medium F is effectively removed of harmful substances contained in the air. At the same time, local early deterioration of the filter medium F can be prevented. In FIG. 6, the distance L from the lower surface of the porous plate 9A to the upper surface of the filter medium F is desirably set in the range of 3 to 5 times the inner diameter d of the vent hole h of the porous plate 9A.

  In the case where the filter 1 filled with the filter medium F with the air gap R formed in the upper part of the filter casing 7 is transported to a place where the air purification device is installed by a vehicle or the like, the filter casing 7 is subjected to shaking or vibration during transportation. In order to prevent the upper surface of the filter medium F from moving and the upper surface of the filter medium F from being inclined, the filter medium F is filled in the casing body 8 and the upper surface is leveled horizontally, and then formed in the void R with a foamed polystyrene resin or the like. It is desirable to pack the rectangular parallelepiped spacer members so that the filter medium F does not move.

  In the above-described air purification filter 1, the front side wall 6 </ b> A of the filter casing 7 is provided with a window portion 13 fitted with a glass plate 12 as a transparent material, and through the glass plate 12, the filter medium F ( Although the color change according to the degree of progress of deterioration of potassium permanganate) can be observed from the outside, the present invention is not limited to this embodiment, and an acrylic plate or the like is used instead of the glass plate 12. The transparent resin material may be used.

  Furthermore, you may form the whole side wall of a filter casing with transparent materials, such as glass and an acrylic resin. Further, the shape of the filter casing is not limited to a box shape as in the above-described embodiment, and may be, for example, a cylindrical shape in which perforated plates are attached to both end faces.

  Furthermore, the filter casing formed in a cylindrical shape with a transparent material may be similarly concentrically incorporated in a cylindrical filter chamber formed with a transparent material. In this case, the filter medium in the filter casing is attached to the filter chamber. It is possible to visually recognize from various directions outside.

  In addition, in the thing of embodiment mentioned above, although the granular potassium permanganate which oxidizes and decomposes and removes harmful substances, such as formalin contained in the air, is used as the filter medium F, the filter medium is used for this. Without being limited thereto, an oxidant such as sodium permanganate that changes color with deterioration in the same manner may be used.

Furthermore, the form of the wall surface flow blocking member 19 described above is not limited to this , and the air length is increased so as to increase the path length in contact with the filter medium by blocking the ventilation path between the inner surface of the side wall of the filter casing and the filter medium. Any device having a function of diverting the flow may be used.

  FIG. 7 and FIG. 8 show another embodiment of the air purification filter of the present invention in which a bubble cushioning material used for general packaging or the like is used for the wall surface flow blocking member. Here, FIG. 8 is an enlarged view of a portion surrounded by a one-dot chain line circle A in FIG. 7, and the filter 1A shown in these drawings uses a large number of cylindrical protrusions V of the bubble cushioning material 23 as wall surface flow blocking members. Yes.

  Note that the filter 1A is obtained by replacing only the wall surface flow blocking member 19 used in the filter 1 described above with the bubble cushioning material 23, and is denoted by the same reference numerals in FIGS. 7 and 8 as those in FIG. Each part has the same structure as the filter 1 in the above-described embodiment.

  As shown in FIG. 8, the bubble cushioning material 23 is formed by bonding a flat polyethylene sheet 23B to the back surface of the polyethylene sheet 23A on which a large number of cylindrical protrusions V are formed. Air is enclosed, and the back surface of the polyethylene sheet 23 </ b> B is bonded to the inner surface of the casing body 8 with a double-sided adhesive sheet 24.

  Since each of the cylindrical protrusions V swells due to the pressure of air sealed inside, the cylindrical protrusions V are flexibly deformed so as to be in close contact with the particles of the filter medium F in contact with the pressure received from the surrounding filter medium F. The contact area with the filter medium F is increased.

  In addition, since many of these cylindrical protrusions V are arranged in a staggered manner on the inner surface of the casing body 8, the flow resistance of the air flow passing through the filter casing 7 is increased by the bubble cushioning material 23. It is guided so as to pass through the inner filter medium F having a smaller flow resistance than the vicinity of the casing main body 8.

  In this embodiment, as shown in FIG. 7, the bubble cushioning material 23 is continuously pasted from the lower end of the inner surface of the side wall of the casing body 8 to the filling height of the filtering material F. As shown in FIG. 2 and the wall surface flow blocking member 19 shown in FIG. 3, a plurality of members that are continuous in a strip shape in the horizontal direction may be pasted in the vertical direction (venting direction).

  The air purifying filter of the present invention can be effectively used in the field of handling harmful substances such as medical universities, research institutions, hospitals and the like.

DESCRIPTION OF SYMBOLS 1, 1A Air purification filter 2 Filter chamber 3 Intake port 4 Exhaust port 5 Air guide plate 6 Porous plate 7 Filter casing 8 Casing body 8A Bottom plate (porous plate)
8a Front wall
8b Rear side wall 8c Left side wall 8d Right side wall 9 Casing lid 9A Top plate (perforated plate)
10 Sealing member 11 Countersunk screw 12 Glass plate (transparent material)
DESCRIPTION OF SYMBOLS 13 Window part 14 Filter opening 15 Cover 15A Observation window 16 Receiving member 17 Positioning member 18 Sealing member 19 Wall surface flow blocking member 20 Fixing member 21 Seal member 22 Wall surface flow blocking member 23 Bubble cushioning material 23A 23B Polyethylene sheet 24 Both surfaces Adhesive sheet F Filter medium R Air gap V Cylindrical protrusion X Air flow h Ventilation hole

Claims (2)

For air purification used in a filter chamber of an air purifier, in which a filter medium having a granular shape is filled in a frame or cylindrical filter casing whose front and rear end surfaces are each composed of a perforated plate. A filter,
In the filter casing , air flow passing through the inside of the filter casing in contact with the inner surface of the side wall is blocked from the inner surface of the side wall by at least a part of the inner surface of the side wall, and the path length in contact with the filter medium is increased. wall flow blocking member to be bypassed, is provided by projecting from the inner surface of the side wall into the filtering material,
For the filter medium, an oxidizing agent whose surface color changes according to the degree of progress of deterioration is used,
At least a part of the side wall of the filter casing is made of a transparent material that can visually recognize the discolored state of the filter material along the ventilation direction from the outside.
On the inner surface of the transparent material, there is a cross-shaped wall-shaped flow blocking member having a square cross section in which the length of one side is substantially perpendicular to the ventilation direction and the length of one side is substantially equal to the average particle diameter of the filter medium. An air purifying filter characterized by being provided .   The filter casing is installed in the filter chamber in such a direction as to vent downward from above, and each passage of the perforated plate is interposed between the upper surface of the filter medium filled therein and the lower surface of the upper perforated plate facing the filter casing. The air purification filter according to claim 1, wherein a gap for decelerating a high-speed air flow that has passed through the pores and diffusing substantially uniformly over the entire upper surface of the filter medium is provided.

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