A movable ventilation device and ventilation method for a box culvert in a tunnel
By using detachable main and branch air ducts in the box culvert inside the tunnel, combined with status detection and gas detection units, the fresh air can automatically follow the movement of the work face, solving the problem of poor ventilation in the box culvert inside the tunnel and improving construction safety and ease of operation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA CONSTR FIFTH ENG DIV CORP LTD
- Filing Date
- 2026-04-22
- Publication Date
- 2026-06-16
AI Technical Summary
In existing technologies, the box culvert structure inside the tunnel is long and narrow, with poor ventilation, making it impossible to deliver fresh air to the work surface. In addition, the ventilation ducts need to be dragged frequently, which is cumbersome and affects construction safety.
The system uses detachable main and branch ducts, combined with status detection and gas detection units. The central controller automatically adjusts the air valves and fans to achieve automatic following of fresh air as it moves across the work surface and gas concentration monitoring. The branch ducts are carried by the operators and directly inserted into the branch duct interface.
It enables fresh air to automatically follow the movement of the work surface, reducing operational complexity and labor intensity, ensuring the safety of workers, and simplifying the process of duct laying and dismantling.
Smart Images
Figure CN122215835A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of tunnel ventilation technology, and in particular to a mobile ventilation device and ventilation method for box culverts inside tunnels. Background Technology
[0002] When installing cable supports and welding in confined underground spaces such as tunnels, box culverts, and pipe galleries, insufficient oxygen or accumulation of toxic and harmful gases often occurs due to the narrow space and poor ventilation. Construction ventilation is a key measure to ensure the safety of workers. The ventilation measures currently used are as follows: A fixed blower is set up at each end of the construction area, using a "one-supply-one-exhaust" ventilation mode. Personnel carry portable oxygen concentration and toxic gas detectors. A dedicated person is stationed at the maintenance port to guard the blower and communicate and coordinate manually via walkie-talkie. Due to the narrow and long box culvert structure inside the tunnel, the cross-section is small and the wind resistance is high. The blower set up at the entrance has a limited effective air supply distance and cannot deliver fresh air to the distant work face. The middle and rear work areas are actually in a state of light wind or even no wind, and the air cannot circulate at all. In addition, the air duct connected to the blower needs to be dragged to the vicinity of the work face by hand. However, as the work face advances, the air duct needs to be dragged and reconnected frequently, which is a cumbersome process.
[0003] Based on the above situation, we propose a mobile ventilation device and ventilation method for box culverts in tunnels to solve the above problems. Summary of the Invention
[0004] This invention provides a mobile ventilation device and method for box culverts in tunnels, to solve the problem in the prior art that fresh air cannot be arbitrarily adjusted according to the movement of personnel working face.
[0005] The technical problem solved by this invention is achieved by the following technical solution: A mobile ventilation device for box culverts inside tunnels includes: A fan, installed outside the box culvert, is used to deliver wind power; The main air supply unit has its input end detachably connected to the air outlet of the fan, and the main air supply unit includes multiple main air ducts. The end of each main air duct is provided with a first quick-release connector, and two adjacent main air ducts are detachably connected through the first quick-release connector. Branch pipe interfaces are located on the main air duct, and each of the branch pipe interfaces is equipped with a control valve; The branch duct, carried by the operator, has its inlet end detachably connected to any of the branch duct interfaces via a second quick-release connector; A status detection unit, located at the branch pipe interface, is used to detect the connection status between the branch pipe and the branch pipe interface and generate a connection signal. The gas detection unit is located at the air outlet of the branch duct and moves synchronously with the branch duct to detect the gas concentration in the work area and generate a gas concentration signal. The central controller is communicatively connected to the fan, control valve, status detection unit, and gas detection unit. The central controller is configured to determine the branch pipe interface to which the branch pipe is connected based on the connection status signal generated by the status detection unit, and to control the opening and closing status and opening degree of the control valve at the corresponding branch pipe interface based on the gas concentration signal generated by the gas detection unit.
[0006] Preferably, the gas detection unit includes multiple gas sensors, a first battery, and a first wireless communication module. The control valve integrates a second battery and a second wireless communication module. The gas detection unit sends the gas concentration signal to the central controller through the first wireless communication module. The central controller sends control commands to the control valve through wireless communication to operate the opening and closing state and opening degree of the control valve.
[0007] Preferably, both the first quick-release connector and the second quick-release connector include a male connector and a female connector. The female connector has an insertion groove, and the male connector has an insertion ring that can be inserted into the insertion groove. The inner wall of the insertion groove has a through hole, and a locking member with a protrusion is slidably connected inside the through hole. The insertion ring has a groove for the protrusion to be engaged. A first spring is connected between the locking member and the through hole. The mating ends of the male connector and the female connector are provided with sealing gaskets.
[0008] Preferably, the female connector has an annular cavity inside, and a release member is slidably connected inside the annular cavity. The release member and the locking member each have parallel abutting slopes at opposite ends. A second spring is provided between the annular cavity and the release member. The release member has an operating ring extending to the outside of the female connector. When the abutting slope on the release member abuts against the abutting slope on the locking member, the locking member compresses the first spring, causing the protrusion to disengage from the groove, thereby achieving a locking connection between the male and female connectors.
[0009] Preferably, the status detection unit is a micro switch disposed in the branch pipe interface. When the male end of the branch pipe is inserted into the branch pipe interface, the front end of the male end presses the micro switch to close it, generating a connection signal. When the male end is pulled out, the micro switch resets and opens, generating a disconnection signal.
[0010] Preferably, the gas detection unit further includes a unique coding module, and the central controller associates the unique coding module of the gas detection unit with the branch pipe interface to determine the current location of the branch pipe interface where the operator carrying the gas detection unit is located.
[0011] Preferably, it also includes a first alarm and a second alarm electrically connected to the central controller. When the first alarm is installed on the ground and the second alarm is installed at the output end of the branch duct, when the gas concentration signal exceeds a preset threshold, the gas detection unit sends an alarm signal to the central controller. After receiving the alarm signal, the central controller triggers the first alarm and the second alarm to issue an alarm.
[0012] The present invention also provides a ventilation method for a mobile ventilation device for box culverts in tunnels, comprising the following steps: S1: Connect multiple main air ducts sequentially through the first quick-release connector to form a main air supply unit extending along the length of the box culvert, and connect the input end of the main air supply unit to the air outlet of the fan. S2: The operator carries the branch pipe into the box culvert. After arriving at the work point, the inlet end of the branch pipe is inserted into the corresponding branch pipe interface through the second quick-release connector. At this time, the status detection unit generates a connection signal and sends it to the central controller. At the same time, the gas detection unit detects the gas concentration in the work area and generates a gas concentration signal and sends it to the central controller. S3: The central controller determines the branch pipe interface to which the branch pipe is connected based on the connection signal, and controls the opening and closing status and opening degree of the control valve at this branch pipe interface and adjusts the output air volume of the fan based on the gas concentration signal.
[0013] The beneficial effects of this invention are: 1. Through the detachable connection between branch ducts and branch duct interfaces, and through the gas detection unit at the output end of the branch duct, fresh air is delivered to the area where the workers are located in sync with the movement of the branch duct and the personnel. The gas concentration in the breathing area of the workers is transmitted to the central controller in real time, so that the controller can automatically adjust the opening of the control valve and the speed of the fan according to the gas concentration, without the need for manual intervention, thus ensuring the safety of the workers. 2. The main duct adopts a segmented design and quick-release connectors, which can be flexibly spliced according to the length of the box culvert. It is easy to lay and disassemble. The branch ducts are carried by the operators and can be directly inserted into the branch duct interface after arriving at the work point. There is no need to drag the entire duct. The operation is simple and the labor intensity is low. Attached Figure Description
[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0015] Figure 1 This is a first-view structural schematic diagram provided for the present invention; Figure 2 This is a schematic diagram of the second-view structure provided by the present invention; Figure 3 This is a schematic cross-sectional view of the male and female connectors when connected in this invention. Figure 4 Provided in this invention Figure 4 Enlarged structural diagram of point A in the middle; Figure 5 This is a schematic cross-sectional view of the male and female heads when separated in this invention. Figure 6 This is a three-dimensional structural diagram of the release component provided in this invention; Figure 7 This is a schematic diagram of the structure when the branch pipe provided in this invention is connected to the branch pipe interface at different locations; Figure 8 This is a schematic diagram of the principle provided in this invention; Figure 9 This is a system block diagram of the alarm provided in this invention; Figure 10 This is a system block diagram of the gas detection unit in this invention; Figure 11 This is a system block diagram of the state detection unit in this invention.
[0016] In the diagram, 1. Fan; 2. Main duct; 21. First quick-release connector; 22. Branch pipe interface; 23. Control valve; 231. Second battery; 232. Second wireless communication module; 3. Branch duct; 31. Second quick-release connector; 4. Central controller; 41. First alarm; 42. Second alarm; 5. Status detection unit; 51. Micro switch; 6. Gas detection unit; 61. Gas sensor; 62. First battery; 63. First wireless communication module; 64. Unique coding module; 7. Male connector; 71. Female connector; 711. Insertion slot; 712. Insertion ring; 713. Through hole; 714. Protrusion; 715. Locking element; 716. Groove; 717. First spring; 718. Sealing gasket; 721. Annular cavity; 722. Release element; 723. Abutting slope; 724. Second spring; 725. Operating ring. Detailed Implementation
[0017] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.
[0018] Reference Figures 1-11As shown, a mobile ventilation device and method for a box culvert within a tunnel includes a fan 1, which is installed outside the box culvert for air delivery. The fan 1 can be a tunnel-specific ventilation fan 1 and is mounted on a mobile trolley for easy and flexible movement. During use, personnel are stationed at the fan 1 to ensure its normal operation. A main air delivery unit is detachably connected to the air outlet of the fan 1. The air delivery unit includes multiple main air ducts 2, and each main air duct 2 has a first quick-release connector 21 at its end. Adjacent main air ducts 2 can be connected via the first quick-release connector 21. Disassembly and connection: When working inside the box culvert, the main air duct 2 can be sent in through the inspection port of the box culvert and assembled inside the box culvert. Each main air duct 2 is also equipped with multiple branch pipe interfaces 22, and each branch pipe interface 22 is equipped with a control air valve 23. Each person working inside the box culvert carries a branch air duct 3, and then installs the branch air duct 3 on the nearest branch pipe interface 22 according to the work area of the worker. It should be noted that both the branch air duct 3 and the main air duct 2 can use PU steel wire telescopic hose or polyurethane hose to enhance wear resistance and facilitate movement inside the box culvert. A status detection unit 5 is provided at the branch pipe interface 22 to detect the connection status between the branch pipe 3 and the branch pipe interface 22 and generate a connection signal. A gas detection unit 6 is provided at the air outlet of the branch pipe 3, which can move synchronously with the branch pipe 3. It is used to detect the decrease in gas concentration in the working area at the air outlet of the branch pipe 3 and generate a gas concentration signal. It also includes a central controller 4 located on the ground. The central controller 4 is communicatively connected to the fan 1, the control valve 23, the status detection unit 5 and the gas detection unit 6. The central controller 4 is configured to determine the branch pipe interface 22 connected to the branch pipe 3 according to the connection status signal generated by the status detection unit 5, and control the opening and closing status and opening degree of the control valve 23 at the corresponding branch pipe interface 22 according to the gas concentration signal generated by the gas detection unit 6. A hook can be provided on the branch pipe 3 so that the branch pipe 3 can be hung on the body and moved synchronously without affecting the operation of personnel. Alternatively, the branch pipe 3 can be placed directly near the working area. When working inside the box culvert, the gas detection unit 6 detects harmful gases near the working face. Once the gas concentration exceeds the set threshold, a signal is transmitted to the central controller 4. The central controller 4 then adjusts the control valve 23 and the fan 1 to regulate the air volume.
[0019] Reference Figure 10As shown, the gas detection unit 6 further includes multiple gas sensors 61, a first battery 62, and a first wireless communication module 63. The control valve 23 integrates a second battery 231 and a second wireless communication module 232. The gas detection unit 6 sends the gas concentration signal to the central controller 4 through the first wireless communication module 63. The central controller 4 sends control commands to the control valve 23 via wireless communication to operate the opening and closing state and opening degree of the control valve 23. The multiple gas sensors 61 can be electrochemical oxygen sensors for detecting oxygen, carbon monoxide sensors for detecting carbon monoxide, etc. The first battery 62 powers the first wireless communication module 63 and the gas sensors 61. The first wireless communication module 63 sends the detected gas concentration to the central controller 4. The second battery 231 powers the second wireless communication module 232 and the control valve 23. The central controller 4 controls the opening degree of the control valve 23 and adjusts the airflow based on the received gas concentration signal sent to the second wireless communication module 232.
[0020] Both the first quick-release connector 21 and the second quick-release connector 31 include a male connector 7 and a female connector 71. The female connector 71 has an insertion groove 711, and the male connector 7 has an insertion ring 712 that can be inserted into the insertion groove 711. The inner wall of the insertion groove 711 has a through hole 713. A locking member 715 with a protrusion 714 is slidably connected inside the through hole 713. The insertion ring 712 has a groove 716 for the protrusion 714 to be engaged. A first spring 717 is connected between the locking member 715 and the through hole 713. When the insertion ring 712 is engaged... When inserted into the insertion slot 711, the locking member 715 is pushed towards the axis of the insertion ring 712 by the action of the first spring 717, so that the protrusion 714 is inserted into the groove 716, realizing the connection between the male head 7 and the female head 71. Both the male head 7 and the female head 71 are provided with elastic sealing gaskets 718. When the male head 7 and the female head 71 are connected, the two elastic sealing gaskets 718 abut against each other to achieve a seal as much as possible and reduce air leakage. This connection method is used between the main air duct 2 and between the branch pipe joint and the branch air duct 3, which is more convenient.
[0021] Reference Figures 3-6 As shown, furthermore, to facilitate disassembly, an annular cavity 721 is provided inside the female head 71. A release member 722 is slidably connected inside the annular cavity 721. The release member 722 and the locking member 715 are both provided with parallel abutting inclined surfaces 723. When the release member 722 moves towards the locking member 715 and abuts against the abutting inclined surface 723 of the locking member 715, the release member compresses the first spring 717, causing the protrusion 714 to disengage from the groove 716, thus releasing the connection between the male head 7 and the female head 71.
[0022] The release member 722 is provided with an operating ring 725 extending to the outside of the female head 71. The release member 722 can be operated through the operating ring 725 on the outside of the female head 71. A second spring 724 is provided between the annular cavity 721 and the release member 722. After the force on the release member 722 is lost, the action of the second spring 724 can cause the abutting slope 723 on the release member 722 to disengage from the abutting slope 723 on the locking member 715, thereby resetting the locking member and the release member 722.
[0023] Reference Figure 5 As shown, the status detection unit 5 is a micro switch 51 installed inside the branch pipe interface 22. The micro switch 51 is installed inside the female connector 71 of the branch pipe interface 22. The two leads of the micro switch 51 are connected to a small circuit board inside the node. The circuit board is powered by the second battery 231. When the male connector 7 of the branch pipe 3 is inserted and the micro switch 51 is pressed to close it, the circuit board detects the switch closure signal and sends a signal that the node has been connected to the central controller 4 through the second communication module 63. When the male connector 7 is pulled out and the micro switch 51 is reset and disconnected, the circuit board detects the disconnection signal and sends a signal that the node has been disconnected to the central controller 4.
[0024] The gas detection unit 6 also includes a unique encoding module 64. The central controller 4 associates the unique encoding module 64 of the gas detection unit 6 with the branch pipe interface 22 it is connected to, in order to determine the current location of the branch pipe interface 22 where the operator carrying the gas detection unit 6 is located. The unique encoding module 64 can be a memory chip with a pre-programmed serial number, or it can be a set of DIP switches. A unique number is set by hardware. For example, the unique encoding module 64 of the gas detection unit 6 carried by operator number 1 is set to code "001"; that of operator number 2 is set to code "002", and so on. At the same time, each branch pipe interface 22 also has a fixed interface identifier, which can also be implemented by an encoding switch or memory chip on the signal processing circuit board at the interface. When the operator inserts the branch pipe 3 into a branch pipe interface 22, the micro switch 51 at the branch pipe interface 22 is triggered, and the signal processing circuit board at the interface then communicates with the second communication... Module 63 sends data to the central controller 4, which includes the identifier of the branch pipe interface 22 (e.g., "branch pipe interface 2203"). At the same time, the gas detection unit 6 also sends data to the central controller 4 through its internal first wireless communication module 63. The data includes the code of its unique coding module 64 (e.g., "001") and the current gas concentration value. After receiving these two frames of data, the central controller 4 establishes a correspondence between "code 001" and "interface 03", thereby determining that the operator of the gas detection unit 6 carrying code 001 is currently located at interface 03. Subsequently, the central controller 4 can control the control valve 23 at interface 03 to open or adjust the air volume according to the gas concentration data sent by the gas detection unit 6. When the operator pulls out the branch pipe and moves to another interface (e.g., interface 05) and inserts it again, the same process will trigger the central controller 4 to re-associate "code 001" with "interface 05", thereby realizing adaptive tracking of the operator's position.
[0025] Reference Figure 9As shown, furthermore, it also includes a first alarm 41 and a second alarm 42. The first alarm 41 is installed on the ground, specifically near the central controller 4 or next to the operating panel of the fan 1, to alert ground monitoring personnel. The second alarm 42 is installed at the output end of the branch duct 3, i.e., close to the breathing area of the operator, to alert the operator. Both the first alarm 41 and the second alarm 42 are electrically connected to the central controller 4. The first alarm 41 can be an audible and visual alarm light, and the second alarm 42 can be a small buzzer or a vibration motor. When the gas detection unit 6 detects... When the gas concentration signal exceeds the preset threshold, the gas detection unit 6 sends an alarm signal to the central controller 4 through the first wireless communication module 63. After receiving the alarm signal, the central controller 4 simultaneously triggers the first alarm 41 and the second alarm 42 to issue an alarm. The first alarm 41 emits a loud audible and visual alarm to alert ground monitoring personnel that the gas concentration at the location of a worker exceeds the standard and that emergency measures should be taken in a timely manner or the status of personnel at the corresponding node should be checked. The second alarm 42 emits a buzzing sound or vibration to directly remind the person currently working to evacuate immediately or take protective measures to improve work safety.
[0026] In addition, the present invention also provides a ventilation method for a mobile ventilation device for box culverts in tunnels, specifically including the following steps: S1: Connect multiple main air ducts 2 sequentially through the first quick-release connector 21 to form a main air supply unit extending along the length of the box culvert, and connect the input end of the main air supply unit to the air outlet of the fan 1. S2: The operator carries the branch pipe 3 into the box culvert. After arriving at the work point, the inlet end of the branch pipe 3 is inserted into the corresponding branch pipe interface 22 through the second quick-release connector 31. At this time, the status detection unit 5 generates a connection signal and sends it to the central controller 4. At the same time, the gas detection unit 6 detects the gas concentration in the work area and generates a gas concentration signal and sends it to the central controller 4. S3: The central controller 4 determines the branch pipe interface 22 connected to the branch pipe 3 according to the connection signal, and controls the opening and closing status and opening degree of the control valve 23 at this branch pipe interface 22 and adjusts the output air volume of the fan 1 according to the gas concentration signal.
[0027] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.
Claims
1. A mobile ventilation device for box culverts inside tunnels, characterized in that, include: A fan (1) is installed outside the box culvert and is used to transport wind power; The main air supply unit has its input end detachably connected to the air outlet of the fan (1), and the main air supply unit includes multiple main air pipes (2). The end of the main air pipe (2) is provided with a first quick-release connector (21), and two adjacent main air pipes (2) are detachably connected through the first quick-release connector (21). Branch pipe interface (22) is provided on the main air duct (2), and each of the branch pipe interfaces (22) is provided with a control air valve (23). Branch duct (3), carried by the operator, has its inlet end detachably connected to any of the branch duct interfaces (22) via a second quick-release connector (31). The status detection unit (5) is located at the branch pipe interface (22) and is used to detect the connection status between the branch pipe (3) and the branch pipe interface (22) and generate a connection signal. The gas detection unit (6) is located at the air outlet of the branch duct (3) and moves synchronously with the branch duct (3) to detect the gas concentration in the work area and generate a gas concentration signal. The central controller (4) is connected to the fan (1), the control valve (23), the status detection unit (5) and the gas detection unit (6) respectively. The central controller (4) is configured to determine the branch pipe interface (22) connected to the branch pipe (3) according to the connection status signal generated by the status detection unit (5), and control the opening and closing status and opening degree of the control valve (23) at the corresponding branch pipe interface (22) according to the gas concentration signal generated by the gas detection unit (6).
2. The mobile ventilation device for box culverts in tunnels according to claim 1, characterized in that, The gas detection unit (6) includes multiple gas sensors (61), a first battery (62) and a first wireless communication module (63). The control valve (23) integrates a second battery (231) and a second wireless communication module (232). The gas detection unit (6) sends the gas concentration signal to the central controller (4) through the first wireless communication module (63). The central controller (4) sends control commands to the control valve (23) through wireless communication to operate the opening and closing state and opening degree of the control valve (23).
3. The mobile ventilation device for box culverts in tunnels according to claim 1, characterized in that, Both the first quick-release connector (21) and the second quick-release connector (31) include a male connector (7) and a female connector (71). The female connector (71) has an insertion groove (711). The male connector (7) has an insertion ring (712) that can be inserted into the insertion groove (711). The inner wall of the insertion groove (711) has a through hole (713). The inside of the through hole (713) is slidably connected to a locking member (715) with a protrusion (714). The insertion ring (712) has a groove (716) for the protrusion (714) to be inserted. A first spring (717) is connected between the locking member (715) and the through hole (713). The mating ends of the male connector (7) and the female connector (71) are both provided with sealing gaskets (718).
4. A mobile ventilation device for box culverts in tunnels according to claim 3, characterized in that, The female head (71) has an annular cavity (721) inside, and a release member (722) is slidably connected inside the annular cavity (721). The release member (722) and the locking member (715) are provided with parallel abutting slopes (723) at opposite ends. A second spring (724) is provided between the annular cavity (721) and the release member (722). The release member (722) is provided with an operating ring (725) extending to the outside of the female head (71). When the abutting slope (723) on the release member (722) abuts against the abutting slope (723) on the locking member (715), the locking member (715) compresses the first spring (717), causing the protrusion (714) to disengage from the groove (716), thereby realizing the locking connection between the male head (7) and the female head (71).
5. A mobile ventilation device for box culverts in tunnels according to claim 1, characterized in that, The status detection unit (5) is a micro switch (51) installed in the branch pipe interface (22). When the male end (7) of the branch pipe (3) is inserted into the branch pipe interface (22), the front end of the male end (7) presses the micro switch (51) to close it and generate a connection signal. When the male end (7) is pulled out, the micro switch (51) is reset and disconnected, generating a disconnection signal.
6. A mobile ventilation device for box culverts in tunnels according to claim 1, characterized in that, The gas detection unit (6) also includes a unique coding module (64). The central controller (4) associates the unique coding module (64) of the gas detection unit (6) with the branch pipe interface (22) to which it is connected, so as to determine the current location of the branch pipe interface (22) where the operator carrying the gas detection unit (6) is located.
7. A mobile ventilation device for box culverts in tunnels according to claim 1, characterized in that, It also includes a first alarm (41) and a second alarm (42) electrically connected to the central controller (4). When the first alarm (41) is installed on the ground and the second alarm (42) is installed at the output end of the branch duct (3), when the gas concentration signal exceeds the preset threshold, the gas detection unit (6) sends an alarm signal to the central controller (4). After receiving the alarm signal, the central controller (4) triggers the first alarm (41) and the second alarm (42) to issue an alarm.
8. A ventilation method for a mobile ventilation device for box culverts in tunnels, based on the mobile ventilation device for box culverts in tunnels as described in any one of claims 1-7, characterized in that, Includes the following steps: S1: Connect multiple main air ducts (2) sequentially through the first quick-release connector (21) to form a main air supply unit extending along the length of the box culvert, and connect the input end of the main air supply unit to the air outlet of the fan (1); S2: The operator carries the branch pipe (3) into the box culvert. After arriving at the work point, the inlet end of the branch pipe (3) is inserted into the corresponding branch pipe interface (22) through the second quick-release connector (31). At this time, the status detection unit (5) generates a connection signal and sends it to the central controller (4). At the same time, the gas detection unit (6) detects the gas concentration in the work area and generates a gas concentration signal and sends it to the central controller (4). S3: The central controller (4) determines the branch pipe interface (22) connected to the branch pipe (3) according to the connection signal, and controls the opening and closing status and opening degree of the control valve (23) at this branch pipe interface (22) and adjusts the output air volume of the fan (1) according to the gas concentration signal.