A toner cartridge for storing toner to be supplied to an image forming apparatus, includes a container in which the toner is stored and including a first wall having a filling port through which the toner is filled, and a second wall having a ventilation port sealable by a plug, the plug sealing the port during operation of the cartridge and is removed during maintenance of the cartridge to enable air to be supplied into the container through the port, a paddle configured to rotate to stir the toner between the first and second walls of the container, and a paddle gear connected to the paddle and through which a rotation force is transmitted to the paddle. The gear has a through hole that aligns with the ventilation port in a first direction parallel to a rotation axis of the gear when the gear is at a predetermined rotational position.

A developing device includes a developer carrier that rotates while holding a developer, a developer container that supports the developer carrier and contains the developer, a transport member that is supported in the developer container and that transports the developer by rotating, and a conveying member that is disposed on the transport member and that conveys air in the developer container toward an exhaust port, which enables the air in the developer container to be exhausted outside, along with rotation of the transport member.

Provided is an inexpensive image forming apparatus capable of monitoring the generating state of various powders. The image forming apparatus includes a minute-particle-measuring device, a toner-particles-detecting air duct, a paper-dust-detecting air duct, and blower fans. The minute-particle-measuring device detects the concentration of minute particles in air. The toner-particle-detecting air duct is an air duct leading from the image forming unit to the minute-particle-measuring device. The paper-dust-detecting air duct is an air duct leading from the paper-conveying path to the minute-particle-measuring device. The blower fans are respectively provided in the toner-particle-detecting air duct and the paper-dust-detecting air duct, and generate airflow that flows toward the minute-particle-measuring device side. The blower fans in the toner-particle-detecting air duct and in the paper-dust-detecting air duct are switched.

Provided is an inexpensive image forming apparatus capable of monitoring the generating state of various powders. The image forming apparatus includes a minute-particle-measuring device, a toner-particles-detecting air duct, a paper dust-detecting air duct, and blower fans. The minute-particle-measuring device detects the concentration of minute particles in air. The toner-particle-detecting air duct is an air duct leading from the image forming unit to the minute-particle-measuring device. The paper-dust-detecting air duct is an air duct leading from the paper-conveying path to the minute-particle-measuring device. The blower fans are respectively provided in the toner-particle-detecting air duct and the paper-dust-detecting air duct, and generate airflow that flows toward the minute-particle-measuring device side. The blower fans in the toner-particle-detecting air duct and in the paper-dust-detecting air duct are switched.

A toner collecting device includes an exhaust path and a catching installation. Through the exhaust path, air containing a floating toner is passed. The catching installation is configured to catch the floating toner from the air passing through the exhaust path. The catching installation is formed by overlapping a plural of filters each having a different mesh size.

In opposition to a sheet feeding path, an ultrafine particle (UFP) collecting filter provided between transfer and fixing is easily exchanged. Therefore, a duct unit kept in a state of holding the UFP collecting filter is removably and easily mounted to a duct.

A developing device includes a developer carrier that rotates while holding a developer, a developer container that supports the developer carrier and contains the developer, a transport member that is supported in the developer container and that transports the developer by rotating, and a conveying member that is disposed on the transport member and that conveys air in the developer container toward an exhaust port, which enables the air in the developer container to be exhausted outside, along with rotation of the transport member.

A developing device includes a developer accommodating container, a developer carrier, an exhaust path, a capturing member, and a closing member. The developer accommodating container accommodates a developer. The developer carrier is disposed in an opening of the developer accommodating container to be rotated while facing an image carrier, and carries the developer. The exhaust path exhausts an air in the developer accommodating container to an outside. The capturing member captures a toner in the exhausted air passing through the exhaust path. The closing member includes a base end portion and a tip end portion. The base end portion is held by the developer accommodating container. The tip end portion is sandwiched between the developer accommodating container and the developer carried on the developer carrier, downstream of the opening in a rotation direction of the developer carrier. The closing member closes a gap.

A developing device includes a developer accommodating container, a developer carrier, an exhaust path, a capturing member, and a closing member. The developer accommodating container accommodates a developer. The developer carrier is disposed in an opening of the developer accommodating container to be rotated while facing an image carrier, and carries the developer. The exhaust path exhausts an air in the developer accommodating container to an outside. The capturing member captures a toner in the exhausted air passing through the exhaust path. The closing member includes a base end portion and a tip end portion. The base end portion is held by the developer accommodating container. The tip end portion is sandwiched between the developer accommodating container and the developer carried on the developer carrier, downstream of the opening in a rotation direction of the developer carrier. The closing member closes a gap.

An image forming device includes an image carrier, a charging device that charges the surface of the image carrier, an electrostatic image forming device that forms an electrostatic image on the surface of the image carrier, a developing device that uses a developer containing toner particles and external additives adhering to the surface of the toner particle to develop the electrostatic image into a toner image, a transfer device that transfers the toner image to a recording medium, a cleaning device having a blade that cleans off residual toner from the image carrier, a suction device that suctions all or part of residual toner excepting the external additives released from the surface of the toner particles, and a fixing device that fixes the toner image to the recording medium.