Intelligent carbon dioxide euthanasia control system and control method for rodent original living cage box

Abstract

The invention relates to an intelligent carbon dioxide euthanasia control system and method for a rodent original living cage box, the system comprises a carbon dioxide gas cylinder, the carbon dioxide gas cylinder is connected with a pressure sensor, an opening adjusting valve, a three-way valve, a valve terminal and a gas inlet silica gel gas nozzle through a pipeline, and the cage box is provided with an in-cage gas sensor; the cage box is sequentially connected with a negative-pressure air draft fan and an air valve through an exhaust silica gel air tap; a tail gas monitoring sensor is arranged on the exhaust pipeline. According to the intelligent carbon dioxide euthanasia system for the rodent original living cage box, the carbon dioxide replacement rate can be accurately controlled, and the gas pressure, the drift diameter, the channel and the like can be accurately controlled; the operation process is simple, software and hardware operation can be rapidly conducted on the system by a single person, gas mixing is uniform, effective and safe locking is achieved, and euthanasia treatment is efficiently conducted on animals in a compliant mode.

Description

Technical Field

[0001] This invention relates to the field of animal experimental devices, and more specifically, to an intelligent carbon dioxide euthanasia control system and control method for rodents in their natural cages. Background Technology

[0002] China's national standard GB / T 39760-2021, "Guidelines for Euthanasia of Laboratory Animals," provides recommendations on the basic principles, conditions, drug selection, and commonly used methods for euthanasia of laboratory animals. It reflects the standardized practice of animal euthanasia within the GLP framework.

[0003] The main contents and considerations include: Basic principles: Emphasizing humanitarianism as the core, ensuring that animals enjoy dignity at the end of their lives, and prioritizing methods that minimize pain, suffering, and anxiety.

[0004] Method Selection: Standards guide the selection of appropriate euthanasia methods, typically considering animal species, age, health condition, and experimental objectives. For example, this may involve drug overdose (such as barbiturates) or physical methods (under specific conditions and using specialized equipment). The key is to choose a reliable method that results in rapid loss of consciousness.

[0005] Personnel operating procedures: Operators must be professionally trained, able to perform euthanasia skillfully and humanely, and able to accurately assess the animal's physiological state.

[0006] Detailed GLP guidelines emphasize complete data recording. The euthanasia process must be documented, including the time, reason, method used, and personnel involved, ensuring traceability of all procedures. Ventilated cages, commonly known as IVCs, are individually ventilated cages. They are feeding devices that provide laboratory animals with a high level of microbial control and a harmless environmental barrier by individually supplying each animal cage with highly efficient filtered clean air and independently exhausting waste gases from the cage.

[0007] Individually ventilated cages (IVCs) are miniature SPF-grade rodent rearing and experimental devices located within sealed, independent living units (cages). They achieve high air exchange rates of clean airflow, independent ventilation, centralized exhaust of waste gases, and can be operated and experimented on within a clean bench. This matrix-style, independently supplied air barrier system, with each cage supplying clean air individually, maintains a specific pressure and cleanliness level to prevent environmental contamination of animals (positive pressure) or animal contamination of the environment (negative pressure). Through airflow organization within the cages and multi-stage filtration, the system ensures animals are protected from microbial contamination. It features an independent control system with adjustable airflow speed and volume, providing excellent barrier protection between humans and animals. It offers advantages such as protecting laboratory animals, protecting operators, protecting the environment, and saving energy.

[0008] Currently, euthanasia of rodents mostly uses individual gas disposal boxes. This requires manually transferring animals from their original IVC cages to a dedicated euthanasia box. The transfer process necessitates processing animals of the same species, sex, and age in batches, while avoiding the introduction of unfamiliar individuals that could trigger stress and aggression. The operation requires operators to manually adjust the carbon dioxide cylinder pressure regulator to control the gas pressure and flow rate, which has drawbacks such as too low a flow rate (prolonging death) or too high a flow rate (causing animal suffering). Furthermore, the number of animals euthanized in a single batch is limited, resulting in low work efficiency.

[0009] Euthanasia of laboratory animals is a core element of laboratory animal ethics. Its core requirement is to use scientifically controlled methods to prevent animals from experiencing pain, panic, and stress before loss of consciousness, while simultaneously ensuring the purity of experimental data. For rodents, carbon dioxide euthanasia has become the mainstream choice due to its advantages such as no drug residue and ease of operation; however, current technology has significant shortcomings, mainly in the following aspects: 1. Insufficient Precision in Concentration Control: Currently, most laboratories use the primitive method of manually switching on and off carbon dioxide cylinders, which cannot achieve a smooth increase in carbon dioxide concentration gradient. Both the Chinese standard GB / T 39760-2021, "Guidelines for Euthanasia of Laboratory Animals," and the American Veterinary Medical Association (AVMA) guidelines for euthanasia of animals clearly require that the euthanasia of rodents using carbon dioxide gas be induced by a precise concentration gradient (10%–30% chamber volume replacement rate per minute). However, manual operation can easily lead to a sudden increase in concentration, causing stress responses such as agitation and rapid breathing in rodents. This violates animal welfare principles and may alter the physiological indicators of rodents, interfering with experimental data.

[0010] 2. Poor adaptability to rodents: Most existing euthanasia devices are general-purpose and not designed for the size of rodents (20-40g mice) and standard cages (approximately 6.5L in volume). For example, patent CN209422160U is only compatible with flat-mouthed cages and is not compatible with the IVC (independent ventilation cage) commonly used for rodents; patent CN216821439U has an excessively large chamber volume, resulting in a carbon dioxide waste rate exceeding 30% during the euthanasia of small batches of rodents, and poor concentration uniformity.

[0011] 3. Lack of disinfection and data traceability: Rodent experiments often involve infectious models. Existing devices (such as CN204907643U) do not have a dedicated disinfection module, and residual pathogens in the chamber can easily lead to cross-infection. At the same time, there is no data recording of concentration, time, etc. during the operation process, which cannot meet the "traceability" requirements of GLP laboratories.

[0012] 4. Lack of personnel safety protection: Some devices do not monitor the carbon dioxide / oxygen concentration in the laboratory environment. When carbon dioxide leaks or oxygen is insufficient (oxygen <19%), it can easily cause dizziness and suffocation risks to laboratory personnel. In addition, there is no automatic exhaust or alarm linkage mechanism, resulting in insufficient safety redundancy.

[0013] While existing technologies have proposed integrated solutions, they suffer from drawbacks such as uneven gas mixing and lack of safety locking: the carbon dioxide concentration gradient is uncontrollable, leading to a high incidence of stress response in mice; the chamber is poorly compatible with standard mouse cages, resulting in low carbon dioxide utilization; and there is a lack of disinfection modules specifically for mouse experiments, which can easily lead to cross-infection.

[0014] Euthanasia of laboratory animals is a core element of the ethical framework for laboratory animals. Its core requirement is to use scientifically controlled methods to prevent animals from experiencing pain, panic, and stress before losing consciousness, while simultaneously ensuring the purity of experimental data. For mice, carbon dioxide euthanasia has become the mainstream choice due to its advantages such as no drug residue and ease of operation; however, current technology has significant shortcomings.

[0015] In summary, existing technologies cannot simultaneously meet the four core requirements of "no stress in rodents", "operational compliance", "safety protection" and "data traceability", and there is an urgent need to develop a precise euthanasia device specifically for rodents. Summary of the Invention

[0016] To address the shortcomings of the existing technology, this invention provides an intelligent carbon dioxide euthanasia control system and method for rodents in their natural cages, which features a controllable carbon dioxide concentration gradient and a low incidence of stress response in mice.

[0017] The technical solution adopted in this invention is: A smart carbon dioxide euthanasia system for rodents in their natural habitat cages includes a carbon dioxide cylinder. The carbon dioxide cylinder is connected to the cage via pipelines to a pressure sensor, a main valve, an opening regulating valve, a flow sensor, a three-way valve, a valve island, and an inlet silicone nozzle. The cage is equipped with an in-cage gas sensor. The cage is connected to a negative pressure exhaust fan, an air valve, and an air outlet via an exhaust silicone nozzle. An exhaust gas monitoring sensor is installed on the exhaust pipeline.

[0018] Preferably, carbon dioxide sensors and oxygen sensors are installed outside the cage.

[0019] A control method for an intelligent carbon dioxide euthanasia control system for rodents in their natural cages includes the following control steps: Step s100, begin; Step s101: Open the valve of the carbon dioxide cylinder, and the carbon dioxide cylinder releases the gas required for euthanasia. Step s102: Open the main valve. Gas enters the opening regulating valve through the main valve. By controlling the opening value of the opening regulating valve, the amount of gas entering the cage is adjusted. Step s103, opening increment control: The opening regulating valve starts with Y1 as the initial opening. Every 10 seconds, the system controls the opening regulating valve to automatically increase the opening by an increment Y3, so that the opening value increases dynamically in a gradient until it reaches the maximum opening Y2 set by the system according to the euthanasia requirements. During this process, the gas flow rate and flow rate increase dynamically with the change of the opening value, thereby achieving a slow increase in concentration. Step s104, opening maintenance control, the opening regulating valve maintains the maximum opening Y2; after this stage is maintained for 30s, the opening value begins to gradually decrease; Step s105, opening decrease control: every 10 seconds, the system controls the opening adjustment valve to decrease by one decreasing opening Y4, so that the opening value decreases dynamically in a gradient. Step s106: The camera monitors the status information of the rodents in the cage; Step s107: Determine if the rodent is still active. If the rodent is still active, proceed to step s108; if the rodent is stationary, proceed to step s112. Step s108: The opening regulating valve stops decreasing the opening and increases the current opening value by one opening Y4; if the current opening value is less than or equal to the maximum opening Y2, then the opening value is maintained unchanged; if the current opening value is greater than the maximum opening Y2, then the opening value is maintained at the maximum opening Y2. Step s109: After a 10-second interval, determine whether the total gas supply time of the system exceeds the system's predetermined time limit; if it exceeds the system's predetermined time limit, proceed to step s110; otherwise, proceed to step s106. In step s110, the system will issue a prompt to notify the operator to make on-site judgments and handle the situation. Step s111: Determine whether the system's scheduled time limit of 60 seconds has been exceeded. If it has, proceed to step s115; otherwise, proceed to step s112. Step s112: The opening adjustment valve decreases by a decreasing degree Y4 every 10 seconds, gradually reducing the opening value to 0, thus closing the opening adjustment valve. Step s113: Each time the opening degree is reduced, it is determined whether the total gas supply time of the system exceeds the system's predetermined time limit; if it exceeds the system's predetermined time limit, proceed to step s110; if it does not exceed the system's predetermined time limit, proceed to step s114. Step s114: Determine if the opening value is zero. If the opening value has not dropped to 0, proceed to step s112; otherwise, proceed to step s115. Step s115: Close the main valve, stop the gas supply, and the cage box enters the 3-minute suffocation stage; Step s116: Open the bypass valve, blower and air valve. The bypass valve sends air into the air duct and cage, and the blower discharges carbon dioxide gas from the air duct and cage. After 5 to 6 minutes of venting, the gas concentration in the cage and air duct is reduced to within a safe range. Step s117: Close the bypass valve, blower, and air valve; close the gas cylinder valve. Step s118, End.

[0020] Preferably, in step s115, the carbon dioxide concentration in the cage is 60% or higher.

[0021] Preferably, carbon dioxide and oxygen sensors outside the cage collect data in real time and transmit the collected data to the central controller. When the collected data exceeds the set safety value, an alarm signal is issued and the main valve is closed.

[0022] The advantages of this invention over the prior art are: This invention relates to an intelligent carbon dioxide euthanasia system for rodents in their natural habitat cages. This system enables stress-free euthanasia by gradually increasing ventilation, raising the carbon dioxide concentration in the cage to 60% or higher within 2 minutes. Compared to traditional methods, it reduces operation time by 90% and the incidence of stress response is ≤5%, which complies with AVMA standards.

[0023] This invention relates to an intelligent carbon dioxide euthanasia system for rodents in their natural habitat cages. The chamber and connector are compatible with 6.5L standard rodent cages and IVC cages, eliminating the need to transfer rodents, avoiding additional stress caused by environmental changes, and increasing carbon dioxide utilization by 20%.

[0024] This invention relates to an intelligent carbon dioxide euthanasia system for rodents in their natural cages. It precisely controls the carbon dioxide replacement rate, including precise control of gas pressure, flow path, and channel. The system is simple to operate, allowing a single person to quickly operate both the hardware and software. It ensures uniform gas mixing, effective and safe locking, and efficient and compliant euthanasia of animals. Attached Figure Description

[0025] Figure 1 A schematic diagram illustrating the gas channel opening adjustment of the intelligent carbon dioxide euthanasia system for rodents in their natural habitat cages according to the present invention; Figure 2 A schematic diagram illustrating the precise control of carbon dioxide gas concentration by the control system. Figure 3 This is a schematic diagram of the device composition of the intelligent carbon dioxide euthanasia system for rodents in their natural habitat cages according to the present invention. Figure 4 This is a schematic diagram of the device control structure of the intelligent carbon dioxide euthanasia system for rodents in their natural habitat cages according to the present invention. Figure 5 The control flowchart of the intelligent carbon dioxide euthanasia system for rodents in their natural habitat cages is shown in this invention. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments: Appendix Figure 1-5 It is known that a smart carbon dioxide euthanasia system for rodents in their natural habitat cages... It includes a carbon dioxide cylinder, which is connected to a pressure sensor, a main valve, an opening regulating valve, a flow sensor, a three-way valve, a valve island, and an inlet silicone nozzle to a cage box via pipelines. The cage box is equipped with a cage gas sensor. The cage box is connected to a negative pressure exhaust fan, a wind valve, and an air outlet in sequence via an exhaust silicone nozzle. An exhaust gas monitoring sensor is installed on the exhaust pipeline.

[0027] Preferably, carbon dioxide and oxygen sensors are installed on the outside of the cage to effectively monitor the operator's working environment.

[0028] The intake silicone nozzle and exhaust silicone nozzle are compatible with mainstream IVC cage interfaces.

[0029] The air outlet is a standard configuration in the laboratory and is not part of the system. The user's laboratory has its own ventilation system that directs the air to the outside. The inlet can be matched with the outlet pipe of our equipment. Our equipment controls the opening and closing of the air valve to achieve connection and isolation with the ventilation system.

[0030] The IVC cage / box interface is a crucial structure connecting the cage rack and cage box, and its design directly affects the system's airtightness, ease of operation, and experimental safety. The interface connects to the cage box via an air nozzle, forming an independent ventilation system that ensures stable air intake and exhaust for each cage box. When the cage box is detached from the cage rack, the air valve on the interface automatically closes to prevent gas leakage. This system uses silicone air nozzles, fully compatible with mainstream cage / box specifications in current laboratory environments, ensuring airtightness and preventing external air ingress or internal gas leakage. It employs a non-invasive structure, with the interface not penetrating deep into the cage box, minimizing disturbance to the animals. It supports quick assembly and disassembly, and the interface design allows for tool-less disassembly, facilitating cleaning and disinfection.

[0031] A smart carbon dioxide euthanasia system for rodents in their natural habitat cages includes a carbon dioxide cylinder. The carbon dioxide cylinder is connected to the cage via pipelines to a pressure sensor, a main valve, an opening regulating valve, a flow sensor, a three-way valve, a valve island, and an inlet silicone nozzle. The cage is equipped with an in-cage gas sensor. The cage is connected to a negative pressure exhaust fan, an air valve, and an air outlet via an exhaust silicone nozzle. An exhaust gas monitoring sensor is installed on the exhaust pipeline.

[0032] Preferably, carbon dioxide sensors and oxygen sensors are installed outside the cage.

[0033] A control method for an intelligent carbon dioxide euthanasia control system for rodents in their natural cages includes the following control steps: Step s100, begin; Step s101: Open the valve of the carbon dioxide cylinder, and the carbon dioxide cylinder releases the gas required for euthanasia. Step s102: Open the main valve. Gas enters the opening regulating valve through the main valve. By controlling the opening value of the opening regulating valve, the amount of gas entering the cage is adjusted. Step s103, opening increment control: The opening regulating valve starts with Y1 as the initial opening. Every 10 seconds, the system controls the opening regulating valve to automatically increase the opening by an increment Y3, so that the opening value increases dynamically in a gradient until it reaches the maximum opening Y2 set by the system according to the euthanasia requirements. During this process, the gas flow rate and flow rate increase dynamically with the change of the opening value, thereby achieving a slow increase in concentration. Step s104, opening maintenance control, the opening regulating valve maintains the maximum opening Y2; after this stage is maintained for 30s, the opening value begins to gradually decrease; Step s105, opening decrease control: every 10 seconds, the system controls the opening adjustment valve to decrease by one decreasing opening Y4, so that the opening value decreases dynamically in a gradient. Step s106: The camera monitors the status information of the rodents in the cage; Step s107: Determine if the rodent is still active. If the rodent is still active, proceed to step s108; if the rodent is stationary, proceed to step s112. Step s108: The opening regulating valve stops decreasing the opening and increases the current opening value by one opening Y4; if the current opening value is less than or equal to the maximum opening Y2, then the opening value is maintained unchanged; if the current opening value is greater than the maximum opening Y2, then the opening value is maintained at the maximum opening Y2. Step s109: After a 10-second interval, determine whether the total gas supply time of the system exceeds the system's predetermined time limit; if it exceeds the system's predetermined time limit, proceed to step s110; otherwise, proceed to step s106. In step s110, the system will issue a prompt to notify the operator to make on-site judgments and handle the situation. Step s111: Determine whether the system's scheduled time limit of 60 seconds has been exceeded. If it has, proceed to step s115; otherwise, proceed to step s112. Step s112: The opening adjustment valve decreases by a decreasing degree Y4 every 10 seconds, gradually reducing the opening value to 0, thus closing the opening adjustment valve. Step s113: Each time the opening degree is reduced, it is determined whether the total gas supply time of the system exceeds the system's predetermined time limit; if it exceeds the system's predetermined time limit, proceed to step s110; if it does not exceed the system's predetermined time limit, proceed to step s114. Step s114: Determine if the opening value is zero. If the opening value has not dropped to 0, proceed to step s112; otherwise, proceed to step s115. Step s115: Close the main valve, stop the gas supply, and the cage box enters the 3-minute suffocation stage; Step s116: Open the bypass valve, blower and air valve. The bypass valve sends air into the air duct and cage, and the blower discharges carbon dioxide gas from the air duct and cage. After 5 to 6 minutes of venting, the gas concentration in the cage and air duct is reduced to within a safe range. Step s117: Close the bypass valve, blower, and air valve; close the gas cylinder valve. Step s118, End.

[0034] Preferably, in step s115, the carbon dioxide concentration in the cage is 60% or higher.

[0035] Preferably, carbon dioxide and oxygen sensors outside the cage collect data in real time and transmit the collected data to the central controller. When the collected data exceeds the set safety value, an alarm signal is issued and the main valve is closed.

[0036] This invention relates to an intelligent carbon dioxide euthanasia system for rodents in their natural habitat cages. This system enables stress-free euthanasia by increasing ventilation, raising the carbon dioxide concentration in the cage to 60% or higher within 2 minutes. Compared to traditional methods, it reduces operation time by 90% and the incidence of stress response is ≤5%, complying with national standards and AVMA specifications.

[0037] This invention relates to an intelligent carbon dioxide euthanasia system for rodents in their natural habitat cages. The chamber and connector are compatible with 6.5L standard rodent cages and IVC cages, eliminating the need to transfer rodents, avoiding additional stress caused by environmental changes, and increasing carbon dioxide utilization by 20%.

[0038] This invention relates to an intelligent carbon dioxide euthanasia system for rodents in their natural cages. It precisely controls the carbon dioxide replacement rate, including precise control of gas pressure, flow path, and channel. The system is simple to operate, allowing a single person to quickly operate both the hardware and software. It ensures uniform gas mixing, effective and safe locking, and efficient and compliant euthanasia of animals.

[0039] Multi-stage pressure reducing and mixing device + oxygen concentration sensor closed-loop control (preferred solution: concentration gradient control completed within 10 minutes).

[0040] like Figure 1 As shown, the intelligent gradient control mode is designed around the core logic of "low stress adaptation (0-50 seconds) - high-efficiency anesthesia (51-80 seconds) - stable deep anesthesia (81-120 seconds)". In the subsequent process, a 3-minute concentration maintenance and a 5-6 minute concentration reduction (ventilation process) ensure the effectiveness of euthanasia and the safety of personnel, before restoring the cage environment to normal. This process achieves a gradual and gradual change in carbon dioxide concentration through precise control of the various electric valves and sensor feedback to perceive the cage and surrounding environment, fully complying with the American Veterinary Medical Association (AVMA) guidelines for euthanizing laboratory animals to "avoid sudden increases in concentration that cause stress".

[0041] The operational logic and equipment linkage mechanism of its three stages are as follows: 1. Concentration Increment Phase (0-50 seconds): Low-stress adaptation period. The core objective is to allow mice to gradually adapt to the carbon dioxide environment and avoid excessive initial concentration differences that could stimulate the respiratory center.

[0042] In the initial stage, the valve opening was gradually increased, and the flow rate data was fed back in real time by a flow meter (0-300L / min range, accuracy 2% Fs). At the same time, the carbon dioxide concentration in the IVC cage was monitored by a sensor to keep it stable within an appropriate range. The activity frequency of the mice was gradually reduced when observed through the transparent cage, which proved that the anesthesia process was gentle and efficient.

[0043] 2. Maximum opening maintenance phase (51~80 seconds): Highly effective anesthesia period.

[0044] Once the mice had adapted to the low concentration, the device entered the anesthesia phase by rapidly increasing the concentration. The valve remained at its maximum opening, and the instantaneous carbon dioxide flow rate monitored by the flow meter reached its peak (approximately 80 L / min). The mice became essentially still, their respiratory rate gradually decreased, and no stress response was triggered.

[0045] 3. Decreasing anesthesia phase (81~120 seconds): Stable deep anesthesia period.

[0046] During this stage, while maintaining the upward trend in concentration, it is crucial to avoid excessively high concentrations later on, which could lead to gas waste. Based on real-time monitoring data from flow meters and sensors, the valve opening is gradually reduced, ultimately stabilizing the carbon dioxide concentration inside the cage at 60% or higher. This fully meets national standards and AVMA's requirement of "10–30% chamber volume replacement rate per minute for euthanasia," laying the foundation for painless death in subsequent stages.

[0047] The above three stages take a total of 2 minutes and are the core of the euthanasia process control. If the gas concentration or flow rate is abnormal, the control system adjusts the valve opening based on feedback data to match the required gas environment. Simultaneously, to ensure a painless death for all mice, a 3-minute suffocation stage and a 5-6 minute venting stage are also required (using a centrifugal fan to reduce the gas concentration in the cage and airway to a safe range). In summary, a complete concentration gradient control and a batch euthanasia operation can be performed within 10 minutes. Figure 2 As shown.

[0048] The entire operation requires no manual transfer; the animal can be quickly and efficiently euthanized within its original IVC cage, perfectly avoiding stress reactions during transfer or introduction to a new environment, and effectively reducing operation time and difficulty. The carbon dioxide replacement rate can be precisely controlled. A feedback pressure sensor (0.2 accuracy, 0~600kPa) accurately measures and calibrates the gas pressure, while a high-precision programmable valve precisely regulates the carbon dioxide airway diameter (0~10mm continuously adjustable). Simultaneously, a high-speed, high-precision flow sensor (2.0%FS accuracy, response <10ms) accurately detects minute flow rates, enabling flow and velocity measurements. Through complete closed-loop control technology, the carbon dioxide replacement rate is precisely controlled.

[0049] The operation process is simple, with an embedded gas filling algorithm that automatically and programmed the entire process according to the flow rate standards for animal euthanasia. It facilitates observation of animal behavior, is equipped with a carbon dioxide concentration monitoring module to record gas concentration changes in real time, and uses a top-intake, bottom-exhaust system to ensure uniform gas distribution in each cage. Once the gas level meets usage requirements, an automatic valve locks the gas state.

[0050] The entire system can be operated quickly by a single person, achieving precise control over the carbon dioxide gas injection, uniform gas mixing, effective and safe locking, and dynamic adjustment of valve opening to achieve automatic parameter optimization.

[0051] Data input and calculation logic: The core of the module is automated calculation based on mathematical models. It uses Huichen PLC's 32-bit ARM Cortex-M4 processor (80MHz main frequency, operation speed ≥100K steps / second) as the computing power core, combined with experimentally verified coefficients, to realize fully automated control parameters.

[0052] When the carbon dioxide gas pressure is constant (the pressure can be adjusted by the pressure reducing valve on the gas cylinder), the flow rate and concentration change curve of carbon dioxide can be affected by precisely controlling the opening value of the regulating valve. The specifications and number of cages correspond to different opening requirements. Through extensive experiments, the dynamic relationship between the opening value and the specifications and number of cages has been obtained and summarized into a set of formula algorithms to cope with different usage scenarios of cage specifications and numbers. That is, for which type of animal (different cage specifications) to be euthanized, and how many animals (number of cages) to be euthanized each time, a reasonable opening change method can be formed to ensure that the gas concentration change is most suitable for the animal's euthanasia needs.

[0053] The specific calculations include: Time parameter calculation: When the basic time parameters (ventilation time, suffocation time, exhaust time) remain unchanged, when the number of cages is large (e.g., more than 15 cages), the PLC will automatically extend the ventilation time by 5-10 seconds to ensure that the carbon dioxide concentration can rise steadily to ≥50% in large-volume scenarios, avoiding insufficient concentration due to excessive volume.

[0054] Valve opening refers to the opening control of an opening regulating valve. The main variable of the system is the opening, which can also be understood as the change in the size of the "bore" in the air passage. The opening of the opening regulating valve is at its maximum of 10, and at its maximum of 0, the valve is closed. All other valves in the system are on / off quantities, i.e., they have two states: open and closed.

[0055] Valve opening parameter calculation: Initial opening Y1=0.05x+0.2, where x represents the number of cages. Ensure that the initial flow rate matches the number of cages to avoid the initial opening being too small when there are a small number of cages (such as x=1), which would cause the concentration to rise too slowly.

[0056] Incremental opening Y3=0.02x: controls the rate of change of opening during the incremental stage, balancing "adaptation effect" and "time efficiency".

[0057] Maximum opening Y2=0.16x+0.24: Ensure that the peak flow rate during the concentration ramp-up phase can quickly reach the level required for anesthesia.

[0058] Decreasing aperture Y4=0.03x: To avoid excessively high concentrations in the later stages, the aperture value is gradually decreased in a stepwise manner, balancing economy and effectiveness.

[0059] Taking x=20 mouse cages (total volume = 6.5×20+16=146L) as an example, the calculated opening parameters are: Y1=1.2, Y2=3.44, Y3=0.4, and Y4=0.6, all within the effective control range of the opening valve (0-10 adjustment range). In actual testing, the concentration of the 20 cages reached 35.46% after 120 seconds, which meets the standard requirements.

[0060] Target flow rate calculation: Combining the total volume of the cage and the carbon dioxide gas mass flow rate measurement range (0-300L / min), the target flow rate value at each moment during the ventilation phase is calculated for comparison with the actual flow rate measured by the flow meter, achieving closed-loop control. For example, when x=20, the total volume is 146L. To ensure the concentration rises to approximately 35% within 2 minutes, the target flow rate is set to 150L / min, corresponding to a 10mA analog output signal from the flow meter (since 0-20mA corresponds to 0-300L / min, a linear relationship). The PLC acquires the actual flow meter signal every 100ms. If the deviation from the target signal is >5% (e.g., target 10mA, actual <9.5mA or >10.5mA), the valve opening is automatically fine-tuned (±0.1 increments) to ensure the flow rate remains stable near the target value.

[0061] Non-professionals do not need to understand the conversion relationship between carbon dioxide concentration and flow rate; they only need to select the cage type and number to complete the parameter settings, significantly lowering the operational threshold. At the same time, standardized calculation logic ensures consistent parameter settings for different operators and different batches of experiments, avoiding inconsistent euthanasia effects due to "human adjustment deviations" (e.g., insufficient concentration in some batches resulting in mice not dying, or excessive concentration in others causing waste). This greatly improves experimental reproducibility and meets the "standardization of experimental procedures" requirements of GLP (Good Laboratory Practice) laboratories.

[0062] Dual-dimensional sensor layout structure: A carbon dioxide sensor is installed inside the cage, combined with a low-concentration carbon dioxide sensor and an oxygen sensor outside the cage, to achieve dual monitoring of the two environments and two gases inside and outside the cage. The carbon dioxide sensor inside the cage is used to monitor the concentration of gases in the cage in real time, ensuring that the euthanasia conditions for laboratory animals are met throughout the process. The data from the carbon dioxide sensor inside the cage is transmitted back to the control system via LORA wireless transmission equipment. Outside the cage, a combination of carbon dioxide and oxygen sensors is used to effectively monitor the operator's operating environment. Real-time gas data is also transmitted back to the control system via LORA wireless transmission equipment. When the indoor operating environment carbon dioxide concentration is >2000ppm or the oxygen concentration is <19%, the equipment will issue an audible and visual alarm to remind the operator to intervene effectively on site to ensure personnel safety.

[0063] like Figure 1 On the parameter adjustment page, users can select the appropriate cage type based on their usage scenario, and the system will automatically calculate the corresponding parameter coefficients for matching. In the parameter adjustment, there are four variables related to the cage opening: Y1, Y2, Y3, and Y4. These are four important opening node data points in the operation of the euthanasia system. They are: Initial opening Y1=0.05x+0.2: Ensure that the initial flow rate is appropriate for the number of cages and avoids the initial opening being too small when there are a small number of cages and avoids the concentration rising too slowly.

[0064] Incremental opening Y3=0.02x: controls the rate of change of opening during the incremental stage, balancing "adaptation effect" and "time efficiency".

[0065] Maximum opening Y2=0.16x+0.24: Ensure that the peak flow rate during the concentration ramp-up phase can quickly reach the level required for anesthesia.

[0066] Decreasing opening degree Y4=0.03x: to avoid excessively high concentration in the later stage, balancing economy and effectiveness.

[0067] Here, X represents the number of cages, and the conversion coefficients and constants between X and Y are related to the cage type (animal type). Different cage types correspond to different combinations of coefficients. This method of parameter template management lowers the barrier to entry for users.

[0068] Timing control interface: During carbon dioxide inflation and maintenance, the corresponding inflation and maintenance times can also be manually changed on the settings page to make personalized adjustments for stationary cage types or special experimental scenarios to meet more application conditions.

[0069] Implementation parameters include: Gas output accuracy: ±0.3% Operating pressure range: 0.2-0.5 MPa; Safety interlock device response time: <200ms; Example of control procedure execution steps: pre-mixing → gradient increase (20% concentration / minute) → maintenance phase → automatic purification.

[0070] The control system intervenes in the gas flow rate and volume, and each execution link is precisely adjustable to achieve the environmental conditions required for the euthanasia of mice.

[0071]

[0072] like Figure 4 As shown, the electrical drives of the important components controlling each link of the airway are all controlled by the PLC host. The main controller of this system adopts the domestic Huichen E7 288-1SR60-0AA1 standard host, which can meet the hardware requirements for direct drive of all peripherals. Its main electrical parameters are as follows:

[0073] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the structure of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A smart carbon dioxide euthanasia system for rodents in their natural habitat cages, characterized in that, It includes a carbon dioxide cylinder, which is connected to a pressure sensor, a main valve, an opening regulating valve, a flow sensor, a three-way valve, a valve island, and an inlet silicone nozzle to a cage box via pipelines. The cage box is equipped with a cage gas sensor. The cage box is connected to a negative pressure exhaust fan, a wind valve, and an air outlet in sequence via an exhaust silicone nozzle. An exhaust gas monitoring sensor is installed on the exhaust pipeline.

2. The method for controlling intelligent carbon dioxide euthanasia in rodent enclosures according to claim 1, characterized in that: Carbon dioxide and oxygen sensors are installed on the outside of the cage.

3. The control method for the intelligent carbon dioxide euthanasia control system for rodents in their natural habitat cages according to any one of claims 1 and 2, characterized in that, The following control steps are included: Step s100, begin; Step s101: Open the valve of the carbon dioxide cylinder, and the carbon dioxide cylinder releases the gas required for euthanasia. Step s102: Open the main valve. Gas enters the opening regulating valve through the main valve. By controlling the opening value of the opening regulating valve, the amount of gas entering the cage is adjusted. Step s103, opening increment control: The opening regulating valve starts with Y1 as the initial opening. Every 10 seconds, the system controls the opening regulating valve to automatically increase the opening by an increment Y3, so that the opening value increases dynamically in a gradient until it reaches the maximum opening Y2 set by the system according to the euthanasia requirements. During this process, the gas flow rate and flow rate increase dynamically with the change of the opening value, thereby achieving a slow increase in concentration. Step s104, opening maintenance control, the opening regulating valve maintains the maximum opening Y2; after this stage is maintained for 30s, the opening value begins to gradually decrease; Step s105, opening decrease control: every 10 seconds, the system controls the opening adjustment valve to decrease by one decreasing opening Y4, so that the opening value decreases dynamically in a gradient. Step s106: The camera monitors the status information of the rodents in the cage; Step s107: Determine if the rodent is still active. If the rodent is still active, proceed to step s108; if the rodent is stationary, proceed to step s112. Step s108: The opening regulating valve stops decreasing the opening and increases the current opening value by one opening Y4; if the current opening value is less than or equal to the maximum opening Y2, then the opening value is maintained unchanged; if the current opening value is greater than the maximum opening Y2, then the opening value is maintained at the maximum opening Y2. Step s109: After a 10-second interval, determine whether the total gas supply time of the system exceeds the system's predetermined time limit. If the system's scheduled time limit has been exceeded, proceed to step s110; Otherwise, proceed to step s106; In step s110, the system will issue a prompt to notify the operator to make on-site judgments and handle the situation. Step s111: Determine whether the system's scheduled time limit of 60 seconds has been exceeded. If the system's scheduled time limit of 60 seconds has been exceeded, proceed to step s115. Otherwise, proceed to step s112; Step s112: The opening adjustment valve decreases by a decreasing degree Y4 every 10 seconds, gradually reducing the opening value to 0, thus closing the opening adjustment valve. Step s113: Each time the opening degree is reduced, it is determined whether the total gas supply time of the system exceeds the upper limit of the system's predetermined time. If the system's scheduled time limit is exceeded, proceed to step s110; if the system's scheduled time limit is not exceeded, proceed to step s114. Step s114: Determine if the opening value is zero. If the opening value has not dropped to 0, proceed to step s112; otherwise, proceed to step s115. Step s115: Close the main valve, stop the gas supply, and the cage box enters the 3-minute suffocation stage; Step s116: Open the bypass valve, blower and air valve. The bypass valve sends air into the air duct and cage, and the blower discharges carbon dioxide gas from the air duct and cage. After 5 to 6 minutes of venting, the gas concentration in the cage and air duct is reduced to within a safe range. Step s117: Close the bypass valve, blower, and air valve; close the gas cylinder valve. Step s118, End.

4. The method for controlling intelligent carbon dioxide euthanasia in rodent enclosures according to claim 3, characterized in that: In step s115, the carbon dioxide concentration inside the cage is 60% or higher.

5. The method for intelligent carbon dioxide euthanasia control in rodent habitat cages according to claim 3, characterized in that: The carbon dioxide and oxygen sensors outside the cage collect data in real time and transmit the collected data to the central controller. When the collected data exceeds the set safety value, an alarm signal is issued and the main valve is closed.

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