An air filter cartridge includes a coiled media pack with inlet flutes and outlet flutes. The coiled media pack has first and second rounded ends with at least a first straight side and a second side. The coiled media pack has: (i) a length extending along a straight line from a center of the first rounded end to a center of the second rounded end; (ii) a first width between the first straight side and second side; the first width being perpendicular to the length; and (iii) a second width thereacross; the second width being perpendicular to the length. The first width is narrower than the second width.

An air filter cartridge includes a coiled media pack with inlet flutes and outlet flutes. The coiled media pack has first and second rounded ends with at least a first straight side and a second side. The coiled media pack has: (i) a length extending along a straight line from a center of the first rounded end to a center of the second rounded end; (ii) a first width between the first straight side and second side; the first width being perpendicular to the length; and (iii) a second width thereacross; the second width being perpendicular to the length. The first width is narrower than the second width.

An air purifying system may include a main air purifier that has a flat upper surface configured to support at least two cylindrical portable air purifiers. Each of the main and portable air purifiers may have a fan to suction air and a filter to filter suctioned air. The upper surface of the main air purifier may include a seating groove, an elastic member provided in the seating groove, and a seating plate resting on top of the elastic member. When a portable air purifier is seated on the seating groove, the elastic member may be compressed and the seating plate may be lowered such that the portable air purifier may be supported within an inner wall of the seating groove. When the portable air purifier is removed from the seating groove, the elastic member may expand and raise the seating plate back to an initial position.

An air purifying system may include a main air purifier that has a flat upper surface configured to support at least two cylindrical portable air purifiers. Each of the main and portable air purifiers may have a fan to suction air and a filter to filter suctioned air. The upper surface of the main air purifier may include a seating groove, an elastic member provided in the seating groove, and a seating plate resting on top of the elastic member. When a portable air purifier is seated on the seating groove, the elastic member may be compressed and the seating plate may be lowered such that the portable air purifier may be supported within an inner wall of the seating groove. When the portable air purifier is removed from the seating groove, the elastic member may expand and raise the seating plate back to an initial position.

A powder container including a filter that separates air and powder from each other, a hopper that includes a first opening portion installed below the filter, a second opening portion that has an opening area that is smaller than that of the first opening portion, and an inclined surface that partially overlaps the filter in plan view, a container box installed so as to be detachable from the hopper, the container box containing the powder, and a detection sensor (an optical sensor) installed outside the container box so as to oppose a side surface of the container box, the detection sensor being installed near the second opening portion and near a side of the inclined surface in a lower direction.

A powder container including a filter that separates air and powder from each other, a hopper that includes a first opening portion installed below the filter, a second opening portion that has an opening area that is smaller than that of the first opening portion, and an inclined surface that partially overlaps the filter in plan view, a container box installed so as to be detachable from the hopper, the container box containing the powder, and a detection sensor (an optical sensor) installed outside the container box so as to oppose a side surface of the container box, the detection sensor being installed near the second opening portion and near a side of the inclined surface in a lower direction.

In an example, a particulate filter includes a porous filter substrate including a first surface and a second surface. The porous filter substrate is configured to filter gas flowing through the porous filter substrate between the first surface and the second surface. A plurality of conductors are coupled to the porous filter substrate. The plurality of conductors are approximately parallel to each other along the porous filter substrate. The particulate filter also includes a plurality of input nodes in signal communication with the plurality of conductors and configured to receive a voltage signal from an input signal source. The plurality of conductors are configured to generate an electric field on at least one of the first surface or the second surface of the porous filter substrate in response to the plurality of input nodes receiving the voltage signal from the input signal source.

In an example, a particulate filter includes a porous filter substrate including a first surface and a second surface. The porous filter substrate is configured to filter gas flowing through the porous filter substrate between the first surface and the second surface. A plurality of conductors are coupled to the porous filter substrate. The plurality of conductors are approximately parallel to each other along the porous filter substrate. The particulate filter also includes a plurality of input nodes in signal communication with the plurality of conductors and configured to receive a voltage signal from an input signal source. The plurality of conductors are configured to generate an electric field on at least one of the first surface or the second surface of the porous filter substrate in response to the plurality of input nodes receiving the voltage signal from the input signal source.

In an example, a particulate filter includes a porous filter substrate including a first surface and a second surface. The porous filter substrate is configured to filter gas flowing through the porous filter substrate between the first surface and the second surface. A plurality of conductors are coupled to the porous filter substrate. The plurality of conductors are approximately parallel to each other along the porous filter substrate. The particulate filter also includes a plurality of input nodes in signal communication with the plurality of conductors and configured to receive a voltage signal from an input signal source. The plurality of conductors are configured to generate an electric field on at least one of the first surface or the second surface of the porous filter substrate in response to the plurality of input nodes receiving the voltage signal from the input signal source.

A dehumidifier comprising: a water tank with a mounting port facing upward, a machine body including an air inlet and a filter net slot beside the air inlet, and a filter net removably inserted in the filter net slot and covering the air inlet. The machine body is configured to be in one of a plurality of states including an idle state in which the machine body is at least partially accommodated in the water tank through the mounting port and a working state in which the machine body is extended out relative to the water tank through the mounting port.