A filter unit (100) includes a rigid filter block (1) that filters out a gas or particles from a gas mixture flowing through the filter unit (100). The filter block (1) has two end faces (Sf.a, Sf.e) and a shell surface (M). A housing including a pot (4) and a cover (2) surrounds the filter block (1). The pot (4) includes a base (4.1) and a tube (4.2). A gap (Sp) occurs between the tube (4.2) of the pot (4) and the shell surface (M) of the filter block (1). Between one end face (Sf.a) of the filter block (1) and the base (4.1) of the pot (4) there is a flat inner area (3.1) of a deformable damping layer (3). An outer area (3.2) of the damping layer (3) surrounds the inner area (3.1) in a circular ring form and is located in the gap (Sp).

A plugged honeycomb structure includes: a honeycomb substrate and a plugging portion, and is configured to trap particulate matter included in fluid flowing from an inflow side end face to an outflow side end face. The partition wall includes, as raw materials, particulates of a base material and a binder and having a melting point lower than that of the base material, the base material has a particle diameter in a range of 5 μm to 60 μm, a mass ratio of the binder to a total mass of the raw material of the base material and the binder is in a range of 22 mass % to 45 mass %, and the cells include round cells as a part, the round cells being defined by a circular-arc partition wall having a circular-arc shape that is at least a part of the partition wall to have a circular shape or the like.

A honeycomb structure includes honeycomb segments each having a porous partition wall defining a plurality of cells, and includes a porous bonding layer containing a crystalline anisotropic ceramic and disposed so as to bond side surfaces of the honeycomb segments to each other. A ratio of a pore volume (cc/g) of a fine pore defined as a pore in the bonding layer having a pore diameter of 10 μm or more and less than 50 μm with respect to a pore volume (cc/g) of a coarse pore defined as a pore in the bonding layer having a pore diameter of 50 μm or more and 300 μm or less is from 2.0 to 3.5, the pore volume of the fine pore is from 0.15 to 0.4 cc/g, and the pore volume of the coarse pore is from 0.05 to 0.25 cc/g.

A plugged honeycomb structure in which in a cross section of a honeycomb structure body which is perpendicular to an extending direction of cells, inflow cells are disposed to surround an outflow cell, and the number of the inflow cells is larger than the number of the outflow cells, and the cross section has a plurality of intersecting portions of partition walls each defining the inflow cells which are adjacent to each other, and in 60% or more of a total number of the intersecting portions, a relation between a diameter (D.sub.1) of a circle inscribed in the intersecting portion and a diameter (D.sub.0) of a circle inscribed in the partition wall defining the inflow cell and the outflow cell which are adjacent to each other satisfies D.sub.1/(√2×D.sub.0)=1.20 to 1.80

An air filter element and air filter system are provided. The filter element has an annular gasket that has multiple portions. A first portion provides axial sealing while a second portion provides only radially sealing. The filter element includes a frame with a radial abutment for engagement with a tooth on a filter housing for providing lateral biasing to the portion of the gasket that provides radial sealing.

A silicon carbide porous body includes a skeletal structure formed by a plurality of silicon carbide particles bonded to each other, a plurality of pores formed by the skeletal structure, neck parts formed by surface-contacting of adjacent silicon carbide particles, and an average pore size is larger than 3 m and equal to or smaller than 9 m, and a porosity ranges from 35% to 55%. A break filter using the silicon carbide porous body enables high performance of collection of particles, prevention of soaring up of particles, and shortening of a restoration time from the depressurized state of the chamber to the atmospheric state.

A plugged honeycomb structure includes: a honeycomb substrate and a plugging portion, and is configured to trap particulate matter included in fluid flowing from an inflow side end face to an outflow side end face. The partition wall includes, as raw materials, particulates of a base material and a binder and having a melting point lower than that of the base material, the base material has a particle diameter in a range of 5 m to 60 m, a mass ratio of the binder to a total mass of the raw material of the base material and the binder is in a range of 22 mass % to 45 mass %, and the cells include round cells as a part, the round cells being defined by a circular-arc partition wall having a circular-arc shape that is at least a part of the partition wall to have a circular shape or the like.

A silicon carbide porous body includes a skeletal structure formed by a plurality of silicon carbide particles bonded to each other, a plurality of pores formed by the skeletal structure, neck parts formed by surface-contacting of adjacent silicon carbide particles, and an average pore size is larger than 3 m and equal to or smaller than 9 m, and a porosity ranges from 35% to 55%. A break filter using the silicon carbide porous body enables high performance of collection of particles, prevention of soaring up of particles, and shortening of a restoration time from the depressurized state of the chamber to the atmospheric state.

A plugged honeycomb structure in which in a cross section of a honeycomb structure body which is perpendicular to an extending direction of cells, inflow cells are disposed to surround an outflow cell, and the number of the inflow cells is larger than the number of the outflow cells, and the cross section has a plurality of intersecting portions of partition walls each defining the inflow cells which are adjacent to each other, and in 60% or more of a total number of the intersecting portions, a relation between a diameter (D.sub.1) of a circle inscribed in the intersecting portion and a diameter (D.sub.0) of a circle inscribed in the partition wall defining the inflow cell and the outflow cell which are adjacent to each other satisfies D.sub.1/(2D.sub.0)=1.20 to 1.80

A honeycomb structure includes honeycomb segments each having a porous partition wall defining a plurality of cells, and includes a porous bonding layer containing a crystalline anisotropic ceramic and disposed so as to bond side surfaces of the honeycomb segments to each other. A ratio of a pore volume (cc/g) of a fine pore defined as a pore in the bonding layer having a pore diameter of 10 m or more and less than 50 m with respect to a pore volume (cc/g) of a coarse pore defined as a pore in the bonding layer having a pore diameter of 50 m or more and 300 m or less is from 2.0 to 3.5, the pore volume of the fine pore is from 0.15 to 0.4 cc/g, and the pore volume of the coarse pore is from 0.05 to 0.25 cc/g.