Section 1 Intelligent Environment of Medical Laboratories

I. Intelligent Control of Ventilation Systems

The intelligentization of ventilation systems makes it possible to monitor and remotely operate all ventilation systems and equipment. From the central control room, fume hoods can be started or shut down, their sash doors raised or lowered, and automatic alarm parameters such as fume hood temperature, air velocity, air volume, and working hours can be set. Automatic start-up or shut-down times for the fume hoods can also be preset, which is particularly suited to experiments that must run for long periods without staff operating them on site. The intelligent ventilation system management software can monitor the ventilation system in real time, automatically record data, and output an Operation Monitoring Report, documenting in detail the operating conditions and faults of each time period; it can also output actual energy-saving data, giving users a clear overview of investment costs and operating costs at a glance. Once the intelligent ventilation system is connected to the Internet, it can be operated from a remote location via mobile phone or computer, and the supplier of the intelligent ventilation system can carry out remote fault diagnosis and maintenance.

[Figure: photograph of a fast-acting electric valve, a cylindrical duct valve with an electric actuator on its side]

Fig. 3-1 Fast-acting electric valve

[Figure: photograph of a fume hood monitor, a tall control panel with a digital display at the top showing 0.52 and a round push button below]

Fig. 3-2 Fume hood monitor [Figure: photograph of a displacement sensor, a light-gray square housing with a metal probe rod extending from one side]

Fig. 3-3 Displacement sensor

[Figure: photograph of a face velocity sensor, a light-gray square panel with a round opening in the center]

Fig. 3-4 Face velocity sensor

[Figure: photograph of a zone status sensor, a white elongated housing with a long black window on the front]

Fig. 3-5 Zone status sensor

Laboratory intelligent airflow control systems and intelligent gas control systems include two types: intelligent gas supply and intelligent gas exhaust. Intelligent gas supply means controlling the high and low pressure values of various gases or negative pressure (the magnitude of the vacuum in negative-pressure systems) by adjusting the upper and lower limits of contact pressure gauges or contact vacuum gauges. When the pressure or vacuum rises to the upper limit or falls to the lower limit, an alarm is triggered; all utility equipment can be automatically controlled through the system control equipment, and its manual/automatic status as well as running and fault statuses are monitored. Intelligent gas exhaust means installing intelligent management software that, through sensitive gas detection probes, detects the content of various gases in the air. The detection signals are sent to the variable air volume control system for processing, which then controls the frequency of the variable-frequency drives and the speed of the exhaust fans, achieving intelligent control of the exhaust system of the laboratory building. Intelligent gas exhaust is particularly suitable for laboratories that use flammable or toxic gases: once a gas leak is detected, the alarm system is promptly activated and ventilation is exhausted, ensuring the safety of personnel and the environment. The intelligent ventilation system is an important hallmark of an international-standard laboratory.

1. Features of the Intelligent Ventilation System

Intelligent: The ventilation volume can be automatically adjusted according to indoor air pollution levels, personnel activity and headcount, humidity, and other conditions, without manual operation. When an exhaust outlet detects a person entering, it instantly opens to maximum in order to rapidly expel odors.

Energy saving: While removing indoor pollution, it can reduce the heat and cooling losses caused by ventilation, and it can automatically adjust the ventilation volume according to the number of people, avoiding unnecessary waste.

Noiseless: The maximum sound attenuation at the air inlet is below 42 dB, and the bare fan unit is below 33 dB, reducing noise to a minimum and even achieving near-silent operation.

2. Control Principles of the Intelligent Ventilation System

The intelligent ventilation system is an upgrade of the ordinary ventilation system and is more intelligent than an ordinary fresh-air system. The fresh-air system with a fully capable heat exchanger can measure air quality by itself; when the machine is switched on, it can automatically carry out air replacement without anyone manually setting the air volume.

2.1 Principle of Fume Hood Variable Air Volume Control

Control method: Fume hood exhaust adopts a TEL variable air volume (VAV) control system with a dual-channel control method, that is, displacement detection together with face velocity detection to control the fume hood face velocity. A dual-sensor approach combining displacement detection and face velocity detection is used to control the fume hood face velocity. First, the displacement sensor detects changes in the opening of the fume hood sash and, within 1 second, controls the butterfly valve to a suitable opening. Once the sash position is stable, the face velocity sensor measures the actual fume hood face velocity and carries out precise fine adjustment. The face velocity sensor detects the fume hood face velocity in real time and promptly raises an alarm if the face velocity is too high or too low. In abnormal situations, the emergency exhaust mode is activated: the control system opens all air valves fully to discharge the maximum air volume the exhaust system can deliver, independent of the face velocity setpoint.

[Figure: schematic diagram of fume hood variable air volume control principle; the fume hood on the left is labeled with a variable air volume butterfly valve, displacement sensor, infrared sensor, and face velocity sensor, connected via red leads to the power supply module at the upper right and downward to the AFA3000 variable air volume controller]

Fig. 3-6 Principle of fume hood variable air volume control

2.2 Room Pressure Control Methods
2.2.1 Room Negative-Pressure Airflow-Tracking (Exhaust-Air) Control Method

Each fume hood variable air volume monitor feeds back the current exhaust air volume and transmits this signal to the room's makeup-air control unit, which calculates the total exhaust air volume. Within the makeup-air control unit, the room's total supply/exhaust air volumes are compared; based on the comparison result, the set air volume of the variable air volume valve is changed so that the supply air follows the exhaust air according to a fixed differential, thereby maintaining the set pressure state in the room. [Figure: three-dimensional schematic of the room negative-pressure airflow-tracking control method, showing the connections between the laboratory supply and exhaust ducts and the variable air volume supply butterfly valve, constant air volume exhaust butterfly valve, variable air volume exhaust butterfly valve, room airflow controller, etc., with the air-conditioning fresh-air unit, exhaust fan, and host computer]

Fig. 3-7 Room negative-pressure airflow-tracking control method

[Figure: photograph of a room local touch panel; the touchscreen displays in separate zones a temperature of 26℃, differential pressure of -5Pa, humidity of 50%, operating status NORMAL, and supply/exhaust air volumes and other parameters]

Fig. 3-8 Room local touch panel

The following status parameters can be sent to the BAS system:

(1) Exhaust air volume of each fume hood in the room

(2) Room negative-pressure status value

(3) Room supply and exhaust air volumes

(4) Room set airflow-tracking (excess exhaust) air volume

(5) Room door position status value

(6) Controller room monitoring status

2.2.2 Room Differential Pressure Detection Control Method

Through a differential pressure sensor, the room negative-pressure status value is monitored in real time. Based on the comparison between the indoor differential pressure value and the set value, the differential pressure controller adjusts the supply air volume so that it reaches a certain matched value with the room's exhaust air volume, thereby controlling the room's negative pressure. [Figure: three-dimensional schematic of the room differential pressure detection control method — inside the laboratory room there are a variable air volume supply butterfly valve (connected to the air-conditioning fresh-air unit), a constant air volume exhaust butterfly valve, and a variable air volume exhaust butterfly valve (connected to the exhaust fan); the room airflow controller connects to each air valve via makeup-air volume and exhaust-air volume signals, and connects via a communication interface to the host computer]

Fig. 3-9 Room differential pressure detection control method

The following status parameters can be sent to the BAS system:

(1) Room negative-pressure status value

(2) Room door position status value

(3) Controller room monitoring status

2.2.3 Compensation Control Method

[Figure: three-dimensional schematic of the room differential pressure compensation control method — in multiple rooms of the laboratory building, fume hoods and laboratory benches are arranged; reddish-brown exhaust ducts and blue supply ducts run through the rooms, and green arrows indicate the direction of outdoor airflow in and out]

Fig. 3-10 Room differential pressure compensation control method

2.3 Principle of Fan Variable-Frequency Control

A constant static pressure control method is adopted to control the variable-frequency operation of the exhaust fan units. According to the power characteristics of fans, when the air volume increases or decreases, the static pressure in the fan duct correspondingly decreases or increases. Therefore, a duct static pressure sensor is installed on the main fan exhaust duct; through the controller and the variable-frequency drive, the fan speed is regulated to maintain the duct static pressure, thereby regulating the system to operate at its original static pressure state. When the system air volume decreases, the goal of variable-frequency energy saving can also be achieved.

[Figure: three-dimensional layout schematic of an exhaust fan unit; a variable-frequency cabinet and a DDC cabinet are connected above the unit, a differential pressure sensor is installed on the main exhaust duct, and arrows indicate the direction of control signal flow]

Fig. 3-11 Schematic diagram 1 of exhaust fan variable-frequency control

[Figure: electrical control principle wiring diagram, including incoming cables, circuit breakers QF1/QF2, contactors KM1–KM4, two VFD variable-frequency drives, and thermal relays; on the right are the pre-reserved DDC power supply, 24V AC power supply, DDC controller, and terminals connecting to the static pressure sensor; the circuits at the bottom are labeled normal fan circuit, standby fan circuit, motor fan connection, and maintenance circuit]

Fig. 3-12 Schematic diagram 2 of exhaust fan variable-frequency control [Figure: schematic diagram 3 of exhaust fan variable-frequency control, an electrical schematic including PE/N/L1 L2 L3 busbars, circuit breakers/contactors, variable-frequency drives, two mutually standby exhaust fans, a duct static pressure sensor, and a TEL static pressure controller with shielded cable]

Fig. 3-13 Schematic diagram 3 of exhaust fan variable-frequency control

2.4 Fresh-Air Air-Conditioning Control
2.4.1 Control Objectives

2.4.1.1 Fresh-air temperature and humidity detection

2.4.1.2 Differential pressure alarm for the primary and intermediate filter sections

2.4.1.3 Control of fresh-air temperature and humidity in winter and summer

2.4.1.4 Fresh-air fan operating status detection and fault alarm

2.4.1.5 Variable-frequency control of the fresh-air fan

2.4.1.6 Interlocks: interlock between the fresh-air fan and the supply air valve status; interlock between the water valve and the fresh-air fan status

2.4.2 Control Methods

2.4.2.1 Supply air temperature and humidity detection

Temperature and humidity sensors are installed at the fresh-air supply outlet to detect the supply air temperature and humidity status.

2.4.2.2 Differential pressure alarm for the primary and intermediate filter sections

Differential pressure switches are installed before and after the filters to detect the differential pressure across the primary and intermediate filter sections. If the detected differential pressure exceeds the filter's rated differential pressure range, a filter blockage alarm is displayed at the workstation.

2.4.2.3 Control of fresh-air temperature and humidity in winter and summer

The supply air temperature and humidity of the fresh-air air-conditioning unit are taken as the actual measured temperature and humidity values and serve as the controlled objects of the air-conditioning system.

In winter, the supply air humidity and temperature are controlled by controlling the hot/chilled water valve and the steam humidification valve. The transition season generally refers to the period when fresh-air temperature and humidity can meet requirements; it is generally left uncontrolled. As needed, this period can be shortened or even eliminated entirely, with that time assigned directly to winter (heating) or summer (cooling) operation.

Supply air control objectives:

Summer: t=25℃ ± 2℃, φ=60% ± 10%

Winter: t=20℃, φ=50% ± 10%

Summer control method:

Control the cooling coil regulating valve to process the air down to the indoor dew point;

Then use the heating coil to bring it to the required supply air temperature.

2.4.2.4 Fresh-air fan operating status detection and fault alarm

A differential pressure switch is used to detect the fresh-air fan operating status, and position feedback signals are taken from both hot and chilled water valves. The system compares the command signals with the feedback signals; if a serious deviation is found, an alarm is raised at the workstation.

2.4.2.5 Variable-frequency control of the fresh-air fan

The fresh-air fan is under variable-frequency control, with start/stop and speed controlled through a variable-frequency drive. The control objective of the speed control loop is the terminal static (differential) pressure of each subsystem, keeping the differential pressure across the butterfly valves in the fresh-air system within their normal operating range. PID control is used; the target setpoint is determined on site, and the initial speed is determined on site.

2.4.2.6 Interlocks

The fresh-air fan is interlocked with the supply air valve status;

The water valve is interlocked with the fresh-air fan status.

[Figure: schematic diagram of exhaust fan variable-frequency control — a combined air-conditioning unit and red air ducts, with arrows connecting the variable-frequency cabinet, DDC cabinet, and differential pressure sensor to indicate control signal relationships]

Fig. 3-14 Schematic diagram of exhaust fan variable-frequency control

2.4.2.7 Start-up and shut-down sequence control

The controller performs the following start-up and shut-down sequences:

Start-up: exhaust fan → fresh-air fan fresh-air valve → fresh-air fan

Shut-down: fresh-air fan → fresh-air valve → exhaust fan

The following status parameters can be sent to the BAS system:

(1) Room fresh-air temperature status value

(2) Primary filter alarm

(3) Intermediate filter alarm

(4) Frost protection status

(5) Fresh-air on/off valve status

(6) Chilled water regulating valve position

(7) Duct temperature and humidity status values

(8) Humidification valve status

(9) Supply fan operating status

(10) Supply fan variable-frequency drive operating frequency

(11) Variable-frequency drive fault alarm

(12) Supply air duct static pressure

(13) Exhaust fan operating status (one in operation, one on standby)

(14) Exhaust fan operating frequency (one in operation, one on standby)

(15) Exhaust fan variable-frequency drive fault (one in operation, one on standby)

(16) Exhaust air duct static pressure

2.5 Laboratory Monitoring
2.5.1 Fume hood system monitoring network connection

All monitors can be connected to the BMS or a monitoring PC, achieving real-time monitoring of each fume hood.

[Figure: network connection schematic of three types of monitoring equipment — fume hood monitors, duct static pressure monitors, and room pressure status monitors — connected via green lines to the BMS host and three monitoring PC displays]

Fig. 3-15 Fume hood system monitoring network connection

2.5.2 Laboratory ventilation automatic control network structure

Achieves central-control network integration of laboratory fume hoods, laboratory room control, and HVAC equipment control.

[Figure: schematic of the laboratory ventilation automatic control network structure; at the top are a monitoring computer and printer, connected via a network bus labeled TCP/IP to multiple groups of field control devices/fume hood control nodes below]

Fig. 3-16 Laboratory ventilation automatic control network structure

2.5.3 Central management station

The central management and operation workstation consists of one computer and one printer. Using a multitasking environment such as Windows as the management and scheduling center of the system, the workstation software realizes centralized supervision and management of the whole system, guidance on operating schemes, and monitoring, scheduling, and management of all controlled equipment, achieving remote control of the equipment.

[Figure: screenshot of the central monitoring system software interface; the title bar shows laboratory Management System Software and TEL; the screen displays a three-dimensional monitoring scene of laboratory fume hoods, with the right side showing supply air 7000CMH, exhaust air 8000CMH, differential pressure 10Pa, temperature 25℃, humidity 50%, and the bottom showing FH01, FH02, FH03, FH04, FH05, FH06 and a Return button]

Fig. 3-17 Central monitoring system 1 [Figure: three Apple iMac all-in-one computers side by side displaying a dark-themed "central monitoring system" software interface; the left and right screens show trend/history curves, and the middle screen shows a data list panel]

Fig. 3-18 Central monitoring system 2

II. Intelligent Control of Clean Air-Conditioning Systems

For a fresh-air purification system to become intelligent, accurate monitoring must first be guaranteed. Air monitors are used to accurately monitor air quality parameters such as PM2.5, temperature, humidity, CO₂, and TVOC (total volatile organic compounds), providing a basis for air filtration and purification and also making the operating effect of the fresh-air purification system directly perceptible so that indoor air quality can be displayed intuitively. Air monitoring results can be displayed intuitively in multiple ways, such as on smart TVs, large screens, PADs, and mobile phones; historical air quality curves can also be viewed and equipment operating effects analyzed, enabling management personnel to keep abreast of air quality and equipment operating conditions in a timely manner. Through the touch panel, equipment operating parameters (PM2.5, CO₂, TVOC, and temperature/humidity thresholds) can be conveniently set; based on real-time detection results and the preset operating parameters, the fresh-air purification equipment (for example, air valve switches, fan speed, and whole-unit on/off) can then operate intelligently. This both saves energy and allows indoor air quality to be customized individually.

The monitoring and control functions and control methods of the intelligent fresh-air unit of the fresh-air purification system are as follows:

  1. Status monitoring and detection. Detect the status of the primary, intermediate, and sub-HEPA filters and fan differential pressure switches, the operating status and fault alarms of the fan variable-frequency drives, and filter clogging alarms.

  2. Temperature and humidity regulation. (1) Automatic control of supply air temperature. In winter, the opening of the hot water valve is automatically adjusted to ensure the supply air temperature is at the set value; in summer, the opening of the chilled water valve is automatically adjusted to ensure the supply air temperature is at the set value. (2) Automatic control of supply air humidity.

  3. Air cleanliness control. By providing three stages of filtration — primary, intermediate, and HEPA air filters — the air is brought to the required cleanliness level.

  4. Fan control. The fan control box is equipped with a manual/automatic selector switch, normally kept in the automatic position. The monitoring center remotely controls the fan through the automatic control system or automatically controls fan start/stop according to a pre-designed time schedule.

  5. Interlock control. The electromagnetic regulating valves and fresh-air dampers are interlocked with fan start-up. When the supply fan starts, the chilled water valve (hot water valve) and fresh-air damper open and the chilled water valve (hot water valve) is regulated; after the fan stops, the fresh/return air dampers, electric regulating valves, and solenoid valves close automatically. After the fan starts, if the differential pressure across it is too large, a fault alarm is triggered and the fan is interlocked to stop. The fresh-air unit is interlocked with the air-conditioning unit: the fresh-air unit must be started before the air-conditioning unit can be started.

The configuration of the various analog input (AI), analog output (AO), digital input (DI), and digital output (DO) points of the fresh-air system is shown in Fig. 3-19.

[Figure: monitoring system diagram of a purification air-conditioning fresh-air unit. The fresh-air duct passes in sequence through the primary filter, supply fan (equipped with a variable-frequency electrical control box), intermediate filter, sub-HEPA filter, surface cooler, and humidifier; monitoring points such as the UV-101 air valve, ultraviolet lamp, TE-101/TE-102 temperature sensors, TV-101 hot/chilled water regulating valve, and MV-101 humidification valve are provided, with cable specifications marked such as 4×1.5, 2×1.5, 8×1.5, and (2×1.5)+(4×1.5); below the diagram is a DDC field wiring table divided into rows for AI, DI, AO, DO, and power supply (24V), with totals of 4, 8, 2, and 3 points on the right, and two rows at the bottom of the table for "wiring number" and "connected DDC box number"]

Fig. 3-19 Monitoring system diagram of a purification air-conditioning fresh-air unit

[Figure: group control diagram of air-conditioning purification system units. Weather hoods connect to the exhaust system and the intake system respectively; the distribution box connects via a stabilized power supply and AC contactors to the main control system; outdoor temperature/humidity sensors, a cleanliness sensor, and indoor temperature/humidity sensors connect to the main control system; the main control system monitors air conditioner 1 and air conditioner 2 separately via current transformers and connects to the host computer via RS485/GPRS]

Fig. 3-20 Group control diagram of air-conditioning purification system units