Ventilation Control Device

Abstract

To provide a ventilation controller capable of more reducing an infection risk based on CO2 concentration in a target space.SOLUTION: A ventilation controller 1 for controlling ventilation in a target space to reduce a risk of infectious diseases, determines a CO2 concentration standard value based on the number of people staying in the target space, and performs control so that a CO2 concentration in the target space is equal to or lower than the CO2 concentration standard value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a ventilation control device that determines a target CO2 concentration standard value in a target space. [Background technology]

[0002] The CO2 concentration is used as an indicator for maintaining a good indoor environment. The Building Sanitation Law's "Building Environmental Sanitation Management Standards" require that the CO2 concentration in indoor air be kept below 1000 ppm. To keep the indoor CO2 concentration below 1000 ppm, a ventilation volume of about 30 CMH (cubic meter per hour) per person is required.

[0003] Generally, when designing air conditioning equipment, the amount of outside air intake and the capacity of the outdoor air conditioner are determined based on the formula "30CMH / person x maximum occupancy density x room area" assuming the maximum occupancy density indoors. Therefore, when the occupancy density is low, the rated operation of the outdoor air conditioner will take in more outside air than necessary. In other words, when the occupancy density is low, adjusting the temperature of the indoor air using the air conditioner consumes a lot of energy.

[0004] Conventionally, a ventilation device has been disclosed that determines the amount of outside air to be introduced by correcting a threshold value of the CO2 concentration in indoor air based on the measurement result of the CO2 concentration in the outside air (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 053946 [Non-Patent Document 1] Rudnick, SN, Milton, DK, Risk of indoor airborne infection transmission estimated from carbon dioxide concentration. Indoor Air 13(3), 237-245., 2003 [Non-Patent Document 2] Brent Stephens: HVAC filtration and the Wells-Riley approach to assessing risks of infectious airborne diseases, Final Report, 2012 Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the ventilation device described in Patent Document 1 can maintain the CO2 concentration below a threshold, it is not necessarily effective against the risk of infection from viruses such as COVID-19. Figures 1 and 2 show images of the occupancy density and infectious particle concentration in a room where the ventilation device is controlled based on the CO2 concentration. Figure 1 shows a case where the infection risk is low, and Figure 2 shows a case where the infection risk is high.

[0007] The CO2 concentration is maintained constant in the rooms shown in Figures 1 and 2. While all people staying in the room are sources of CO2, only infected people are sources of infectious particles. Therefore, as the person density decreases, the ratio of CO2 generated by infected people to the total amount of CO2 in the room increases. In other words, as the person density decreases, the amount of exhaled breath of infected people lingering in the room, that is, the amount of infectious particles, increases. Therefore, if the CO2 concentration is controlled to a constant level regardless of the person density, the risk of infection is higher when an infected person is in a room with a low person density as shown in Figure 2 than when an infected person is in a room with a high person density as shown in Figure 1.

[0008] Conventional CO2 concentration-based management methods for maintaining a good indoor environment were designed to keep the total amount of indoor pollutants generated by people in the room below a certain level. Therefore, in a situation where infectious particles are emitted from some infected people among the people in the room, this was sometimes insufficient to reduce the risk of infection. Therefore, the present invention provides a ventilation control device that can calculate a target CO2 concentration in a target space and further reduce the risk of infection based on the calculated CO2 concentration. [Means for solving the problem]

[0009] The ventilation control device according to the present invention comprises: A ventilation control device for controlling ventilation in a target space to reduce the risk of infectious diseases, A CO2 concentration standard value is determined based on the number of people in a target space, and the CO2 concentration in the target space is controlled to be equal to or lower than the CO2 concentration standard value. It is characterized by: Effect of the Invention

[0010] According to the ventilation control device of the present invention, it is possible to further reduce the risk of infection based on the CO2 concentration in the target space. [Brief description of the drawings]

[0011] [Figure 1] This is an image of the occupancy density and infectious particle concentration in a room with CO2 concentration control, showing a case where the risk of infection is low. [Diagram 2] This is an image of the relationship between occupancy density and infectious particle concentration in a room with CO2 concentration control, showing a case where the risk of infection is high. [Diagram 3] 1 shows an example of a system structure of a ventilation control device of the present embodiment. [Figure 4] 4 shows an image of changing control settings of the ventilation control device of this embodiment. [Diagram 5] 4 shows an example of a flowchart of ventilation control according to the present embodiment. [Figure 6] The standard CO2 concentration is shown for the number of people staying in a conference room. [Figure 7] The standard CO2 concentration is shown for the number of people assumed to be staying in an office. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a ventilation control device 1 according to one embodiment of the present invention will be described with reference to the drawings. The ventilation control device 1 of this embodiment controls to reduce the risk of infection with an infectious disease in a target space based on the number of people staying in a room (the number of people staying) and the outdoor air CO2 concentration. Here, the ventilation control device 1 of this embodiment targets airborne infection, and does not target droplet infection or contact infection in which infectious particles do not remain in the air due to dynamic settling. Infectious particles are, for example, mold, bacteria, or viruses.

[0013] It is assumed that infectious particles, such as droplet nuclei, remain suspended in the air for a long period of time. Such infectious particles are spread indoors through exhaled air, including sneezing and coughing. The concentration of CO2 contained in human exhaled air varies depending on the amount of movement of the person, but generally ranges from about 10,000 ppm to 90,000 ppm, compared to 350 ppm to 400 ppm in outdoor air. In addition, in most indoor buildings, the source of CO2 is human exhaled air, so CO2 is effective as a marker of exhaled air exposure.

[0014] The ventilation control device 1 of this embodiment is designed to change the CO2 concentration standard value for the target space. Therefore, as long as information on people in the target space can be obtained, it can be applied to existing air conditioning systems. The information on people only needs to know the number of people staying in the target space.

[0015] Note that the ventilation control device 1 of this embodiment will be described with respect to the CO2 concentration control within a target space that is managed by one ventilation control device 1. There may be multiple target spaces within one room.

[0016] FIG. 3 shows an example of a system structure of the ventilation control device 1 of this embodiment.

[0017] The ventilation control device 1 of this embodiment comprises at least a detection unit 10 that detects conditions inside and outside the target space, an input unit 20 that inputs predetermined parameters, and a control unit 30 that changes the ventilation control settings based on information from the detection unit 10 and the input unit 20.

[0018] The detection unit 10 has a human detection sensor 11 that detects the number of people staying in the target space, and an outside air CO2 concentration sensor 12 that measures the concentration of CO2 in the outside air.

[0019] The human detection sensor 11 detects the number of people staying in a target space such as a specified room, and inputs the number of people to the control unit 30. The human detection sensor 11 may be one that detects wireless tags distributed in advance when people enter a room, one that analyzes images taken with a camera or the like, one that recognizes people by laser scanning or the like, one that detects temperature by infrared rays or the like, or the like.

[0020] The outside air CO2 concentration sensor 12 is installed in the outside air to measure the concentration of CO2 and input the measured value to the control unit 30. The outside air CO2 concentration sensor 12 may be an optical type such as an NDIR (Non Dispersive Infrared Gas Anaryzer), an electrochemical type using an electrochemical reaction, a semiconductor type using a semiconductor such as tin oxide, or the like.

[0021] The input unit 20 has at least an attribute input unit 21 for inputting an estimated time that a person will stay in the target space, and an infectious disease parameter input unit 22 for inputting information related to an infectious disease.

[0022] The attribute input unit 21 inputs the representative stay time t of the target space, which has been set in advance by the administrator, to the control unit 30. The representative stay time t is a time that the administrator assumes for each target space, taking into consideration the use of the target space, and is set by the administrator. For example, if the target space is a conference room, the administrator assumes the stay time to be about 1 to 2 hours, and sets the representative stay time t to 2 hours in the attribute input unit 21. Also, if the target space is an office, the administrator assumes the stay time to be about 8 hours, and sets the representative stay time t to 8 hours in the attribute input unit 21.

[0023] The infectious disease parameter input unit 22 inputs a plurality of infectious disease parameters having constant values ​​preset by the administrator to the control unit 30. The infectious disease parameters include three parameters: the number of infected people I, the CO2 concentration Ca in the breath of building users (stayers) including the infected people, and the amount of infectious particles generated by droplet nuclei q emitted by the infected people. The CO2 concentration Ca in the breath of building users varies depending on the building, and the number of infected people I varies depending on the infection status of the building users. The amount of infectious particles generated q also varies depending on the infectious disease. For this reason, the number of infected people I, the CO2 concentration Ca in the breath, and the amount of infectious particles generated q listed as the infectious disease parameters may be set by the administrator based on the characteristics of the infectious disease, the infection status of the building users, the use of the building, and the like. Details of each infectious disease parameter in this embodiment will be described later.

[0024] The control unit 30 determines the infection probability reference CO2 concentration C at which the infection probability in the target space is equal to or lower than a certain level. p Or the basic reproduction number standard CO2 concentration C where the basic reproduction number is below a certain level R and a CO2 concentration standard value selection unit 32 that compares the CO2 concentrations calculated by the CO2 concentration calculation unit 31 and selects the lower one. The system may also have a control setting change unit 33 that changes the setting of the CO2 concentration control proportional band using the CO2 concentration standard value selected by the CO2 concentration standard value selection unit 32. R When comparing, a calculated reference CO2 concentration may be set.

[0025] First, the infection probability reference CO2 concentration C calculated by the CO2 concentration calculation unit 31 p This article explains:

[0026] The probability of infection is evaluated using the modified Wells-Riley model proposed by Rudnick and Milton in Non-Patent Document 1. The following formulas (A-1) and (A-2) are expressed as the number of people n in the target space detected by the human detection sensor 11, the outdoor air CO2 concentration C detected by the outdoor air CO2 concentration sensor 12, oThe calculation can be performed by inputting the representative stay time t set by the attribute input unit 21 and the infectious disease parameters set by the infectious disease parameter input unit 22.

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[0027] Exhaled CO2 concentration during light work C a is about 38,000 ppm, and the outside air CO2 concentration C o The CO2 concentration in the exhaled breath is about 350-400 ppm. a By setting the value as a constant, the work intensity of the person and the outside air CO2 concentration C o By setting the value as a constant, it is possible to calculate the infection risk distribution by assuming that the outside air conditions are constant conditions without using the output of the detection unit 12.

[0028] From formula (A-1) and formula (A-2), the infection probability standard CO2 concentration C p is expressed as the following equation (1).

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[0029] The infection probability is the probability that an infected person infects a non-infected person in a specific space. The infection probability is a value between 0 and 1, and the manager (facility manager) sets a target infection probability P a For example, if there is one infected person in the target space and the administrator wants to keep the infection probability of each non-infected person below 30%, the administrator determines the target infection probability P a is set to 0.3. Note that the basic reproduction number standard CO2 concentration C R In order to match this, we always assume that the number of infected people in the target space is I = 1.

[0030] In this way, the CO2 concentration calculation unit 31 calculates the target infection probability P a By determining the infection probability standard CO2 concentration C p can be calculated.

[0031] Next, the basic reproduction number standard CO2 concentration C, which is calculated by the CO2 concentration calculation unit 31 so that the basic reproduction number of the population is equal to or less than a certain value, is calculated. R When the basic reproduction number falls below 1, the spread of infection in a population will come to an end. The basic reproduction number can be thought of as the number of new infections D for each infected person I = 1 in formula (A-2).

[0032] Therefore, we substitute I = 1 and S = n-1 into equation (A-2) and calculate the basic reproduction number from the following equation (B).

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[0033] Also, from equation (B), the basic reproductive number standard CO2 concentration C R is calculated using the following formula (2).

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[0034] In this way, the basic reproduction number, which indicates how many people one infected person can spread the infection to, is set as a target value by the manager (facility manager) from the perspective of reducing the risk of infection in the target space. Aa The CO2 concentration calculation unit 31 determines the target basic reproduction number R Aa Based on the basic regeneration arithmetic standard CO2 concentration C R can be calculated.

[0035] The CO2 concentration standard value selection unit 32 selects the infection probability standard CO2 concentration C p and the basic reproductive number standard CO2 concentration C calculated using equation (2) R As shown in formula (C), the lower CO2 concentration is set as the CO2 concentration standard value C s Select as.

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[0036] FIG. 4 shows an image of changing the control settings of the ventilation control device of this embodiment. The horizontal axis of the graph shown in FIG.s and the vertical axis represents the inverter output of the outside air introduction fan serving as the outside air introduction unit 40.

[0037] The control setting change unit 33 changes the selected CO2 concentration reference value C s Change the setting of the CO2 concentration control proportional band using the CO2 concentration reference value C s The inverter output of the outside air introduction section 40 of the ventilation system 100 is adjusted by performing proportional control having a proportional band with respect to the CO2 concentration reference value C s If the above is changed, problems such as excessively large airflow even when there are only a few people present may occur.

[0038] The control setting change unit 33 changes the CO2 concentration reference value C s The magnitude of the initial proportional band α is changed according to the change in . The magnitude of the corrected proportional band B is changed according to the following equation (3).

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[0039] For example, in the example shown in Figure 4, the initial CO2 concentration standard value C b is set to 900 ppm, and the initial proportional band α is 200 ppm. O is 400 ppm, CO2 concentration standard value C s is 500 ppm, the corrected proportional band B is 40 ppm.

[0040] In this way, the outdoor CO2 concentration C O CO2 concentration standard value C close to s By setting the corrected proportional band B, the control accuracy is improved. OCO2 concentration standard value C close to s When is set, the lower limit of the proportional band is the outside air CO2 concentration C O can be prevented from falling below

[0041] Next, a method for changing the control settings of the ventilation control device 1 of this embodiment will be described.

[0042] FIG. 5 shows a control setting change flowchart for the ventilation control device 1 of this embodiment.

[0043] First, in step 1, the ventilation control device 1 inputs the value detected by the detector 10 and the infection parameters input from the input unit 20 to the control unit 30 (ST1).

[0044] Next, in step 2, the CO2 concentration calculation unit 31 calculates the infection probability reference CO2 concentration C p and the basic reproduction number standard CO2 concentration C R Calculate at least one of the following (ST2).

[0045] Next, in step 3, the CO2 concentration reference value selection unit 32 selects the infection probability reference CO2 concentration C p and the basic reproductive number standard CO2 concentration C R The lower CO2 concentration is set as the CO2 concentration standard value C s (ST3).

[0046] Next, in step 4, the control setting change unit 33 changes the selected CO2 concentration reference value C s Use to change the setting of the CO2 concentration control proportional band (ST4).

[0047] In this way, the risk of infection can be reduced by changing the control settings of the ventilation control device 1. It is preferable to start this flowchart at regular intervals.

[0048] Next, examples of changing the control settings are shown based on the example parameters shown in Table 1. [Table 1]

[0049] The target space is a conference room and an office, and the CO2 concentration standard value C is set according to the number of people staying there. s Change the setting.

[0050] Figure 6 shows the standard CO2 concentration for the number of people staying in a conference room.

[0051] As shown in Figure 6, the infection probability standard CO2 concentration C p increases in proportion to the number of people staying in the area. This is because the more people stay in the area, the more CO2 emissions from non-infected people increase. On the other hand, the basic reproduction number standard CO2 concentration C R decreases as the number of people in the room increases.

[0052] CO2 concentration standard value C in the conference room s When the number of people staying is four or less, the infection probability standard CO2 concentration C p If the number of people staying is 5 or more, the basic reproduction number standard CO2 concentration C R In this example, even if the number of people staying increases, the basic reproductive number standard CO2 concentration C R The basic reproduction number standard CO2 concentration C R If the change in the basic reproduction number standard CO2 concentration C is known through prior verification, it will be compared with the number of people in the conference room. R It may be fixed as follows.

[0053] Figure 7 shows the standard CO2 concentration for the number of people assumed to be in an office.

[0054] As shown in Figure 7, the infection probability standard CO2 concentration C p increases in proportion to the number of people staying, and the basic reproduction number standard CO2 concentration C R However, because it is assumed that people stay in the office for a longer period of time than in the conference room, the standard CO2 concentration C p ,C R Both are low.

[0055] CO2 concentration standard value C in the office s When the number of people staying is four or less, the infection probability standard CO2 concentration C p If the number of people staying is 5 or more, the basic reproduction number standard CO2 concentration C R applies.

[0056] The ventilation control device 1 described in this embodiment is preferably used in a ventilation system 100 that performs ventilation in a target space. The ventilation system 100 includes a ventilation control device 1 and a CO2 concentration reference value C s and an outside air introduction section 40 that introduces outside air into the target space according to the target space. Also, a discharge section that discharges air from the target space may be provided. The outside air introduction section 40 may be a structure included in an existing air conditioning device.

[0057] As described above, the ventilation control device 1 of this embodiment is a ventilation control device 1 for controlling ventilation in a target space to reduce the risk of infection, and determines a CO2 concentration standard value based on the number of people staying in the target space, and controls the CO2 concentration in the target space to be equal to or lower than the CO2 concentration standard value. Therefore, the ventilation control device 1 of this embodiment can further reduce the infection risk based on the CO2 concentration in the target space.

[0058] In addition, the ventilation control device 1 of this embodiment calculates a CO2 concentration standard value C at which the infection probability in the target space is below a certain level or the basic reproduction number is below a certain level based on the number of visitors n, the representative stay time t that the expected visitors will stay in the target space, the number of infected people I in the target space, the CO2 concentration Ca of the exhaled breath of building users (visitors) including infected people, and the amount of infectious particles generated by droplet nuclei emitted by infected people q. s Therefore, according to the ventilation control device 1 of the present embodiment, it is possible to further reduce the risk of infection based on the CO2 concentration in the target space.

[0059] In addition, the ventilation control device 1 of this embodiment further receives the CO2 concentration of the outside air as an input, and calculates the number of visitors n and the CO2 concentration C o, the representative stay time t that an expected occupant stays in the target space, the number of infected people in the target space I, and the CO2 concentration in the breath of building users (occupants) including infected people C a , and the CO2 concentration standard value C at which the infection probability in the target space is below a certain level or the basic reproduction number is below a certain level based on the amount of infectious particles generated by droplet nuclei of an infected person q. s Therefore, according to the ventilation control device 1 of the present embodiment, it is possible to further reduce the risk of infection based on the CO2 concentration in the target space.

[0060] In addition, the ventilation control device 1 of this embodiment defines a CO2 concentration at which the infection probability in the target space is equal to or lower than a certain level as an infection probability reference CO2 concentration C p The CO2 concentration at which the basic reproduction number falls below a certain level is called the basic reproduction number standard CO2 concentration C R The infection probability standard CO2 concentration C p is calculated from the above formula (1) and is the basic reproduction number standard CO2 concentration C R is calculated from the above formula (2). Therefore, according to the ventilation control device 1 of the present embodiment, it is possible to further reduce the risk of infection based on the CO2 concentration in the target space.

[0061] In addition, the ventilation control device 1 of this embodiment is configured to set the CO2 concentration reference value C s The setting of the CO2 concentration control proportional band is changed according to the above formula (3) using the above. Therefore, according to the ventilation control device 1 of the present embodiment, it is possible to further reduce the infection risk based on the CO2 concentration in the target space.

[0062] It should be noted that the present invention is not limited to the embodiments, and that although many specific details are included for illustrative purposes in the description of the embodiments, those skilled in the art may make various variations and modifications to these details. [Explanation of symbols]

[0063] 1...Ventilation control device 10: detection unit, 11: human detection sensor, 12: outside air CO2 sensor 20: input section, 21: attribute input section, 22: infectious disease parameter input section 30... control unit, 31... CO2 concentration calculation unit, 32... CO2 concentration reference value selection unit, 33... control setting change unit 40…Outside air intake

Claims

1. A ventilation control device that determines a CO 2 concentration standard value based on the number of people staying in a target space in order to control ventilation in the target space to reduce a risk of infectious diseases, and controls the CO 2 concentration in the target space to be equal to or lower than the CO 2 concentration standard value, The CO 2 concentration standard value C s at which the infection probability in the target space is below a certain level or the basic reproduction number is below a certain level is calculated from the number of visitors, the expected representative stay time of the visitors in the target space, the number of infected people in the target space, the CO 2 concentration in the breath of the visitors, and the amount of infectious particles generated by droplet nuclei of the infected people. A ventilation control device comprising:

2. Outside air CO ２ The concentration is also taken as input, The number of visitors, the CO ２ concentration, the expected typical stay time of the visitor in the target space, the number of infected people in the target space, and the CO ２ The CO concentration and the amount of infectious particles generated by droplet nuclei of the infected person are used to determine whether the infection probability in the target space is below a certain level or the basic reproduction number is below a certain level. ２ Concentration reference value C ｓ Ask for The ventilation control device according to claim 1 .

3. CO that reduces the infection probability in the target space to a certain level or less ２ CO concentration as infection probability standard ２ Concentration C ｐ year, The CO that the basic reproduction number is below a certain level ２ Concentration is the basic reproduction number standard CO ２ Concentration C Ｒ year, The infection probability criterion CO ２ Concentration C ｐ is calculated from the following formula (1), and the basic reproduction number standard CO ２ Concentration C Ｒ is calculated from the following formula (2): The ventilation control device according to claim 2 . [0010] Where: n: Number of people in the target space [people], C ｏ : Outside air CO ２ Concentration [ppm], t: Stay time [h], C ｐ : Infection probability standard CO ２ Concentration [ppm], P ａ : Target infection probability, C Ｒ :Basic Regeneration Arithmetic Standard CO ２ Concentration [ppm], R Ａａ : Target basic reproduction number [people] C ａ : Exhaled CO added to exhaled air during breathing ２ Concentration [ppm], q: infectious particle generation amount by droplet nuclei [quanta / h], It is.

4. The CO ２ Concentration reference value C ｓ Using CO ２ The concentration control proportional band is changed according to the following formula (3). The ventilation control device according to claim 3 . [0025] Where: B: Corrected proportional band [ppm], C ｂ : Initial CO ２ Concentration standard value [ppm], α: Initial proportional band [ppm] It is.

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