JP7545941B2 - Air Purifying Negative Pressure Device - Google Patents

Description

The present invention relates to an air purification negative pressure device that purifies the air in a room while maintaining a negative pressure in the room.

Filter units that capture and purify fine particles in polluted air using a HEPA (High Efficiency Particulate Air) filter before discharging the air are widely known and used to turn polluted air into clean air. They are primarily used in medical institutions and research facilities for the purpose of capturing and normalizing bacteria and viruses. Patent Document 1 describes how indoor air is purified by passing it through a HEPA filter and then exhausted to the outside by an exhaust fan.

JP 2001-178785 A

The structure of a conventional example of an air purification filter unit for creating negative pressure in a hospital room is shown in Figure 10. Figure 10 is a cross-sectional view showing the structure of an air purification filter unit 80 in a conventional example. By driving the fan motor 86 and rotating the fan 85, air in the hospital room is sucked in and introduced into the air purification filter unit 80 from the suction part 82 of the exhaust HEPA filter unit. The sucked in air passes through the HEPA filter 81, and the air purified by the HEPA filter 81 is exhausted to the outside through the exhaust port 87 by the rotation of the fan 85.

In addition, it is desirable to place parts requiring maintenance such as motor replacement and cleaning on the exhaust side of the HEPA filter of the exhaust HEPA filter unit. If a fan or fan motor requiring maintenance such as replacement is placed on the intake side of the HEPA filter, the air before being purified by the HEPA filter passes through the fan or fan motor, causing viruses and bacteria floating in the air to adhere to the fan or fan motor. There is a risk of workers becoming infected from viruses and bacteria adhering to the fan or fan motor during subsequent maintenance of the filter unit, so it is preferable to place fans or fan motors requiring maintenance such as replacement on the exhaust side of the purification filter.

When carrying out a performance evaluation test to check the performance of the HEPA filter 81 or to confirm that there are no problems with the installation of the HEPA filter 81, for example, a measurement port 88 for the performance evaluation test is temporarily attached to a part of the filter unit 80, and the measurement port 88 is connected to a particle sensor that measures fine particles for measurement. In the conventional example shown in Figure 10, an example is shown in which the measurement port 88 for the performance evaluation test is temporarily attached to the back side of the suction part 82.

As a result, because the measurement port 88 was a temporary mounting position, it was impossible to accurately evaluate the cleaning performance of the filter when the filter unit was in normal use.

It is also possible to measure at the blowing surface of the HEPA filter 81 by using a removable cover on the rear side of the suction section 82 on the front side. However, in this case, when the fan 85 is rotated, contaminated air is sucked into the filter unit through the opening of the removable cover on the rear side, and the contaminated air does not pass through the HEPA filter 81, so it is necessary to install another fan upstream of the HEPA filter 81.

In light of the above, there was a demand for a filter unit that would enable performance evaluation tests to be performed under normal operating conditions, while also improving the ease of routine maintenance such as motor replacement, filter replacement, and cleaning of the filter unit.

The present invention provides an air purification negative pressure device that improves the accuracy of performance evaluation tests for air purification filters while improving the ease of routine maintenance work, and has a compact configuration that allows for easy installation.

To solve the above problem, an example of an air purifying negative pressure device includes a filter chamber having an intake section provided on the front of a housing that draws in air containing fine particles from inside a room, and a purification filter that purifies the air drawn into the intake section by passing it backward, a duct that provides an air flow path extending in a direction substantially perpendicular to the air flow path direction that passes backward through the purification filter, and a rear chamber having an intake port that draws in air inside the duct and is provided at substantially the center of the longitudinal direction of the front wall of the duct, a fan that draws in air flowing out of the rear chamber forward, a fan motor that drives and rotates the fan, an exhaust port that discharges the air drawn in by the fan to the side, and a cover that allows the front of the housing to be opened. The device has a configuration including: a filter chamber having an intake section provided on the front of a housing that draws in air containing fine particles from inside the housing, and a purification filter that purifies the air drawn into the intake section by passing the air backward through the purification filter; a duct that provides an air flow path extending in a direction substantially perpendicular to the air flow path direction that passes backward through the purification filter, and a rear chamber having an intake port that draws in air inside the duct and is provided at substantially the center of the longitudinal direction of the front wall of the duct; a fan chamber having a fan that draws in air flowing out of the rear chamber forward, a fan motor that drives and rotates the fan, a exhaust port that discharges air drawn in by the fan to the side, and a cover that allows the front of the housing to be opened; and a connection section that allows a measuring device outside the housing that measures the purification performance of the purification filter to be connected to the intake port from the front of the housing.

The present invention improves the accuracy of performance evaluation tests for air purification filters while improving the ease of routine maintenance work, and allows for easy installation with a compact configuration.

FIG. 1 is a configuration diagram showing an installation state of an air cleaning negative pressure device 100 in a first embodiment. 1 is a cross-sectional view showing the internal structure of an air cleaning negative pressure device 100 according to a first embodiment, viewed from above. FIG. 2 is a perspective view of the bell mouth 14 in the first embodiment as viewed from the cleaned air flow D side. 2 is a schematic diagram for explaining the measurement principle of a particle counter 60 in the first embodiment. FIG. 4 is a graph showing the measurement results of a particle counter 60 in Example 1. FIG. 11 is a configuration diagram showing the installation state of an air cleaning negative pressure device 200 in a second embodiment. FIG. 11 is a configuration diagram showing the installation state of an air cleaning negative pressure device 300 in the third embodiment. FIG. 11 is a configuration diagram showing the installation state of an air cleaning negative pressure device 400 in a fourth embodiment. FIG. 13 is a configuration diagram showing the installation state of an air cleaning negative pressure device 500 in a fifth embodiment. FIG. 11 is a cross-sectional view showing the structure of an air cleaning filter unit 80 in a conventional example.

The embodiments will be described in detail with reference to the drawings. However, the present invention should not be interpreted as being limited to the description of the embodiments shown below. Those skilled in the art will easily understand that the specific configuration can be changed without departing from the concept or spirit of the present invention.

The position, size, shape, range, number, etc. of each element shown in the drawings are merely examples to facilitate understanding of the invention, and the position, size, shape, range, and number of each element are not limited to those disclosed in this specification and the drawings. They can be modified as appropriate to suit each embodiment. Note that in the following examples, multiple similar elements are arranged, and some of the elements will be described as representative.

Figure 1 is a configuration diagram showing the installation state of the air cleaning negative pressure device 100 in Example 1. In Figure 1, the air cleaning negative pressure device 100 is installed on the wall surface of a negative pressure room 1. The negative pressure room 1 is mainly intended as a hospital room or a bacteriology laboratory, and is a space in which the air in the room is cleaned and exhausted by driving a fan described below, while maintaining negative pressure in the room and preventing the spread of infection.

The air purification negative pressure device 100 takes in contaminated air flow A containing dust with viruses, bacteria, etc. attached, purifies it, and then discharges it to the outside as purified air flow B. Thus, the air purification negative pressure device 100 is a device that purifies the air in the negative pressure room 1 by collecting dust in the air, and prevents infection by maintaining negative pressure.

The internal structure and operation of the air cleaning negative pressure device 100 will be described in detail below. Figure 2 is a cross-sectional view of the internal structure of the air cleaning negative pressure device 100 in Example 1, viewed from above. The housing of the air cleaning negative pressure device 100 is separated into three chambers: a fan chamber 10, a filter chamber 20, and a rear chamber 30. In Figure 2, the upper part of the figure indicates the rear side, and the lower part of the figure indicates the front side.

The filter chamber 20 is a filter chamber provided with an intake section 22 on the front side and a cleaning filter 21 inside. The cleaning filter 21 has a structure including an outer frame that holds the filtering material, using glass fiber as the filtering material and a light metal such as aluminum that is anodized and clear-coated. The above-mentioned structure shows a general structure of the cleaning filter 21, and is not limited to this structure. For example, a material that is easily available, such as nonwoven fabric, may be used as the filtering material. The filter chamber 20 draws in indoor air from the intake section 22 on the front side, passes the air through the cleaning filter 21 inside, and discharges the air to the rear. The intake section 22 can be opened and closed forward.
The rear chamber 30 is provided on the rear side of the filter chamber 20, and includes a duct that provides an air flow path extending in a direction approximately perpendicular to the direction of the air flow path that has passed rearward through the purification filter 21. In Fig. 2, air is sent out to the right side of Fig. 2 on the rear side of the filter chamber 20.

A fan chamber 10 is provided to the side of the filter chamber 20 and in front of the rear chamber 30. The fan chamber 10 is an exhaust chamber that has a bellmouth 14 at the suction port from the rear chamber 30, a fan 12 inside, a fan motor 11 that drives and rotates the fan 12, a motor mounting base 15 to which the fan motor 11 is fixed, a duct flange 13 as an exhaust port, and a cover 42 on the front.

The fan 12 is a rotating blade that has a rotating shaft that is rotated by the fan motor 11 and multiple fins of a predetermined shape around the rotating shaft, for example, four fins if the fan has four blades. The negative pressure conditions can be optimized by designing the rotation speed of the fan motor 11 and the diameter of the fins on the fan 12 in conjunction with the bell mouth 14 described below.

In FIG. 2, contaminated air flow A is taken in by the suction section 22 of the air cleaning negative pressure device 100. The taken in contaminated air flow A is purified by the purification filter 21 in the filter chamber 20 and flows out as purified air flow C to the rear chamber 30 at the rear. The purified air flow C flows through the rear chamber 30, which extends in a direction approximately perpendicular to the air flow path direction that passed through the purification filter 21, and is drawn in by the suction of the fan 12 like purified air flow D, and is taken into the fan chamber 10 in front of the rear chamber 30.

The purified air flow D taken into the fan chamber 10 is discharged to the outside as purified air flow B through the bell mouth 14 and duct flange 13 by the rotation of the fan 12. The fan 12 is driven to rotate by the fan motor 11, and purifies the air in the room by drawing air from the room through the air flow path of the filter chamber 20, rear chamber 30, and fan chamber 10, and maintains a negative pressure in the room by exhausting the air from the duct flange 13 as an exhaust port.

The bellmouth 14 is a suction section for adjusting the suction pressure sucked into the fan chamber 10. Figure 3 is an oblique view of the bellmouth 14 in Example 1, seen from the side of the purified air flow D. By appropriately designing the inner diameter of the bellmouth 14, the outer diameter of the fins of the fan 12, and the rotation speed of the fan 12, it is possible to make the suction pressure of the fan chamber 10 more efficient in relation to the driving power of the fan motor as an air flow with good negative pressure efficiency, and also to adjust the degree of negative pressure in the room.

The filter chamber 20, rear chamber 30, and fan chamber 10 are each formed into a partitioned box shape, which prevents the contaminated air flow before purification by the purification filter 21 from flowing into the fan chamber 10 before exhaust, ensuring that the air purification function of the air purification device is fulfilled. Furthermore, the manufacturing and assembly process is simplified by combining these three chambers.

The air purified by the purification filter 21 is taken into the rear chamber 30. In the rear chamber 30, a measurement port 40 is provided on the air flow path where the purified air flow C flows into the purified air flow D by the rotational suction of the fan 12. The measurement port 40 is a suction port provided on the air flow path where the purified air flows from C to D, at approximately the center of the longitudinal direction of the front wall of the duct. If the measurement port 40 is positioned too close to either the purification filter 21 or the fan 12, there is a possibility that dust particles near the purification filter 21 or the fan 12 may be detected, and the detection accuracy may decrease. Therefore, the position of the measurement port 40 is preferably approximately the center of the purification filter 21 and the fan 12 in the air flow path in the rear chamber 30.

A tube 41 can be connected to the measurement port 40. The front end 41a of the tube 41 is disposed at the front of the air cleaning negative pressure device 100 and is a connection part that allows a particle counter 60 to be connected to the outside of the device.

The particle counter 60 is a measuring instrument capable of measuring the particle size and number of particles of fine particles, and obtains performance evaluation measurements of the purification filter 21. FIG. 4 is a schematic diagram explaining the measurement principle of the particle counter 60 in Example 1. The air flow inside the rear chamber 30 is drawn into the particle counter 60 with a predetermined suction force through the tube 41. The air flow drawn from inside the rear chamber 30 is discharged into the particle counter 60 by the nozzle 61, and the discharged air flow is irradiated with laser light from the laser light source 62. If fine particles are contained in the air flow irradiated with the laser light, the laser light is scattered by the fine particles. The degree of scattering of the laser light is imaged by the condenser lens 63 and detected by the light receiving element 64, making it possible to detect the fine particles.

The measurement principle shown in Figure 4 gives the measurement results shown in Figure 5. Figure 5 is a graph showing the measurement results of the particle counter in Example 1. A pulse waveform as shown in Figure 5 is obtained from the output voltage of the detection result of the light receiving element 64, with the peak size indicating the particle size of the particles and the number of pulses indicating the number of particles. As shown in Figure 5, by measuring the particle size and number of particles in the air, it is possible to measure the performance of the purification filter 21. However, the particle sensor 60 does not depend on the detection principle and measurement result configurations as shown in Figures 4 and 5.

In this way, the air purification negative pressure device 100 in Example 1 makes it possible to measure the air flow in the rear chamber 30 along the air flow path under normal use conditions, making it possible to perform performance evaluation tests of the purification filter 21 under normal use conditions with high accuracy from the front side of the device housing.

In addition, in FIG. 2, by opening the cover 42 located on the front, maintenance work such as replacing the fan 12 and fan motor 11 and cleaning the inside of the air cleaning negative pressure device 100 can be performed from the front side of the air cleaning negative pressure device 100. As described above, both the performance evaluation test under normal use conditions of the cleaning filter 21 and the maintenance work can be performed from the front side of the device housing, improving workability.

The air purification negative pressure device of this embodiment, with the above-mentioned configuration, has the effect of reducing the amount of viruses and bacteria in the negative pressure room and weakening their infectiousness by collecting dust with viruses and bacteria attached in the negative pressure room with the purification filter 21. In addition, by discharging the air purified by the purification filter 21 to the outside, it has the effect of preventing the spread of infection from viruses and bacteria in the negative pressure room to the outside.

As shown in FIG. 2, the air purifying negative pressure device 100 is made up of a housing in which the filter chamber 20 and the fan chamber 10 are arranged in parallel, with the rear chamber 30 arranged at the rear. The rear chamber 30 is a flow path member provided to form an air flow path from the filter chamber 20 to the fan chamber 10, and has a depth of about 70 to 100 mm. Therefore, even if the filter chamber 20 and the fan chamber 10 are arranged in front of the rear chamber 30, the air purifying negative pressure device 100 can be used as a thin and compact device housing. In addition, the manufacturing process is also simplified, since the three chambers, the filter chamber 20, the rear chamber 30, and the fan chamber 10, are manufactured separately and then the three chambers are finally combined to form a housing.

As described above, the air purifying negative pressure device 100, which is configured as a compact device housing, can be easily installed on the wall of a room, and because of the improved workability as described above, for example, a general hospital room can be easily renovated into an infectious disease control room, and maintenance is also easy.

According to the first embodiment, the housing is configured with a filter chamber 20 having a purification filter 21, a rear chamber 30 at the rear, and a fan chamber 10 having a fan 12. A measurement port 40 for evaluating the performance of the purification filter is provided in the approximate center of the rear chamber, and a connection part 41a for connecting to the measurement port 40 and a cover 42 for maintenance work are provided on the front of the housing, thereby improving the accuracy of the performance evaluation test of the air purification filter and improving the ease of daily maintenance work, and providing an air purification negative pressure device with a compact configuration that can be easily installed.

Furthermore, as mentioned above, by appropriately designing the correspondence between the inner diameter of the bell mouth 14, the fan fin diameter, and the fan rotation speed, the suction pressure in the fan chamber 10 can be made more efficient in relation to the driving power of the fan motor, and the degree of negative pressure in the room can also be adjusted. This leads to a reduction in the driving power of the fan motor, which reduces carbon emissions caused by the driving power, prevents global warming, and has the effect of protecting the environment and leading to the realization of a sustainable society.

The air cleaning negative pressure device 200 in Example 2 will be described below. FIG. 6 is a configuration diagram showing the installation state of the air cleaning negative pressure device 200 in Example 2. In Example 2, the description of the same components as in Example 1 will be omitted. The difference from Example 1 is that a port guard 50 is provided as a barrier downstream in the air flow direction flowing around the measurement port 40.

In FIG. 6, air is drawn into an external particle counter 60 from a measurement port 40 to measure the airflow, but the airflow velocity may be too high to be drawn into the measurement port 40 properly. If the airflow velocity around the measurement port 40 is too high, a port guard 50 can be provided to reduce the airflow velocity around the measurement port 40, allowing accurate measurement by the particle counter. The port guard 50 is a straightening member with an L-shaped cross section.

According to the second embodiment, the port guard 50 is provided as a straightening member, which prevents measurement problems from occurring when air is sucked into the particle counter 60 provided outside, and makes it possible to adjust the performance evaluation measurement accuracy when measuring the performance of the purification filter 21.

The air cleaning negative pressure device 300 in Example 3 will be described below. FIG. 7 is a configuration diagram showing the installation state of the air cleaning negative pressure device 300 in Example 3. In Example 3, the same components as in Example 2 and Example 1 will not be described. The difference from Example 1 is that a port guard 51 is provided as a barrier downstream in the air flow direction flowing around the measurement port 40.

In FIG. 7, air is sucked into the particle counter 60 from the measurement port 40 to measure the airflow, but the airflow may not be sucked into the measurement port 40 properly if the airflow speed is too high. The port guard 51 is a straightening member with an opening 51a on the downstream side of the airflow direction of its L-shaped cross section. The longitudinal position of the opening (perpendicular to the paper surface) is determined taking into account the position of the measurement port. By providing the opening 51a on the downstream side as in the port guard 51 shown in FIG. 7, the airflow around the measurement port 40 can be sucked in properly, and the deterioration of measurement accuracy, which would be caused by dust accumulating in the port guard 50 shown in Example 2, can be suppressed, which would otherwise cause more particles to be detected than in a normal air flow path.

According to the third embodiment, the port guard 51 is provided as a straightening member, which prevents measurement problems from occurring when air is drawn into the particle counter 60 provided outside, makes it possible to adjust the performance evaluation measurement accuracy when measuring the performance of the purification filter 21, and prevents a decrease in measurement accuracy due to dust accumulation inside the port guard.

The air cleaning negative pressure device 400 in Example 4 will be described below. FIG. 8 is a configuration diagram showing the installation state of the air cleaning negative pressure device 400 in Example 4. In Example 4, the description of the same components as in Example 1 will be omitted. The difference from Example 1 is that a port guard 52 is provided to rectify the air flow around the measurement port 40.

In FIG. 8, air is drawn into the particle counter 60 from the measurement port 40 to measure the airflow, but the airflow velocity may be too high to draw the airflow into the measurement port 40. The port guard 52 is a straightening member having a mountain-shaped configuration as shown in FIG. 8. By making it into a mountain-shaped configuration as shown in FIG. 8, the airflow around the measurement port can be straightened, and the measurement accuracy decrease due to the accumulation of dust can be suppressed, which would otherwise cause the detection of more particles than in a normal air flow path. Furthermore, the airflow passing above the port guard 52 can be straightened, suppressing pressure loss in the rear chamber 30.

According to the fourth embodiment, by providing a port guard 52 as a straightening member, measurement problems occurring when air is sucked into the particle counter 60 installed outside can be prevented, the performance evaluation measurement accuracy when measuring the performance of the purification filter 21 can be adjusted, and pressure loss in the rear chamber 30 can be suppressed.

The air cleaning negative pressure device 500 in Example 5 will be described below. FIG. 9 is a configuration diagram showing the installation state of the air cleaning negative pressure device 500 in Example 5. In Example 5, the same points as in Example 1 will not be described. The difference from Example 1 is that a port guard 53 is provided to rectify the air flow around the measurement port 40.

In FIG. 9, air is sucked into the particle counter 60 from the measurement port 40 to measure the airflow, but the airflow may not be sucked into the measurement port 40 properly if the airflow speed is too high. The port guard 53 is an upright straightening member provided to prevent the airflow in the rear chamber 30 from directly hitting the measurement port 40, as shown in FIG. 9. By making it upright as in FIG. 9, turbulence is generated in the rear chamber 30, and if there is a leak inside the air cleaning negative pressure device 500, the turbulence can diffuse particles into the rear chamber 30. By diffusing the particles in the rear chamber 30 and reducing the airflow speed around the measurement port 40, the measurement accuracy of the particle counter 60 is improved.

According to the fifth embodiment, the port guard 53 is provided as a straightening member, which prevents measurement problems from occurring when air is drawn into the particle counter 60 provided outside, and if there is a leak inside the air cleaning negative pressure device 500, the turbulent flow can diffuse the particles into the rear chamber 30. By diffusing the particles in the rear chamber 30 and reducing the air flow speed around the measurement port 40, the measurement accuracy of the particle counter 60 is improved.

In the above, in Examples 2 to 5, embodiments in which the port guards 50 to 53 provided around the measurement port 40 have various shapes have been described. As described above, by designing the shapes of the port guards 50 to 53, the inner diameter of the bell mouth 14, the fin diameter of the fan 12, and the rotation speed of the fan 12 in correspondence with each other, it becomes possible to adjust the amount of air suction at the measurement port 40, and to optimize the performance measurement accuracy of the purification filter 21. By optimizing the performance measurement accuracy of the purification filter 21, an air purification negative pressure device is provided that is more efficient in terms of drive power and design labor.

In addition, by adjusting the inner diameter of the bell mouth 14, the fin diameter of the fan 12, and the rotation speed of the fan 12 in a corresponding manner, it is possible to adjust the exhaust pressure to the duct flange 13 and optimize the degree of negative pressure created by the air purification negative pressure device.

In the first to fifth embodiments, the filter chamber and the fan chamber are arranged side by side in the housing configuration, but they may be arranged one above the other. In this case, the housing will be elongated vertically, and this configuration is suitable for cases where an elongated vertical arrangement is preferable due to limitations in the installation space.

1: Negative pressure room 10: Fan chamber 11: Fan motor 12: Fan 13: Duct flange (exhaust port)
14: Bell mouth (suction part)
20: Filter chamber 21: Cleaning filter 22: Suction section 30: Rear chamber 40: Measurement port (suction port)
41a: Tube front end (connection part)
42: Cover 50, 51, 52, 53: Port guard (flow straightening member)
60: Particle sensor

Claims (9)

A filter chamber having an intake section provided on a front surface of a housing for sucking in air containing fine particles from inside a room, and a cleaning filter for passing the air sucked in through the intake section backward to clean it;
a rear chamber including a duct providing an air flow path extending in a direction substantially perpendicular to the direction of the air flow path that has passed rearward through the cleaning filter, and a suction port provided in a front wall surface of the duct at a substantially central position in the longitudinal direction thereof for sucking in air within the duct;
a fan chamber including a fan that draws in the air discharged from the rear chamber forward, a fan motor that drives and rotates the fan, an exhaust port that discharges the air drawn in by the fan from a side to the outside of the room, and a cover that allows the front surface of the housing to be opened;
An air cleaning negative pressure device comprising: a measuring device outside the housing for measuring the cleaning performance of the cleaning filter; and a connection portion that enables the measuring device to be connected to the suction port from the front surface of the housing . Further, a straightening member is provided to adjust the air flow in the vicinity of the suction port,
The air cleaning negative pressure device according to claim 1, wherein the airflow straightening member is provided on a front wall surface of the duct. 3. The air cleaning negative pressure device according to claim 2, wherein the airflow straightening member is L-shaped with a surface perpendicular to the air flow direction in the duct provided downstream of the suction port in the air flow direction. 4. The air cleaning negative pressure device according to claim 3, wherein the airflow straightening member has an opening on a surface perpendicular to the air flow direction in the duct. 3. The air cleaning negative pressure device according to claim 2, wherein the airflow straightening member is a mountain-shaped member that is inclined with respect to the air flow direction in the duct and is disposed near the suction port. 3. The air cleaning negative pressure device according to claim 2, wherein the airflow straightening member has an upright shape with a surface perpendicular to the airflow direction in the duct provided upstream of the suction port in the airflow direction. 2. The air cleaning negative pressure device according to claim 1, wherein the cleaning filter can be replaced from the front side of the housing by opening the suction section. a suction section is further provided at an inlet through which air is sucked from the rear chamber to the fan chamber;
The air cleaning negative pressure device according to claim 2, characterized in that the accuracy of performance evaluation of the cleaning filter can be adjusted by correspondingly adjusting the shape of the straightening member, the inner diameter of the suction part, the fin diameter of the fan, and the rotation speed of the fan. a suction section is further provided at an inlet through which air is sucked from the rear chamber to the fan chamber;
2. The air cleaning negative pressure device according to claim 1, wherein the degree of negative pressure in the room can be adjusted by adjusting the inner diameter of the suction part, the fin diameter of the fan, and the rotation speed of the fan.

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