Particulate pollutants in the air are composed of solid or liquid microparticles. The particle size distribution of these particles varies widely, ranging from 0.01 μm to several hundred micrometers. Particles larger than 10 μm, being heavier, gradually settle to the ground under the influence of gravity after a period of random Brownian motion, whereas particles smaller than 10 μm, being lighter, easily float with air currents and are difficult to settle to the ground. It is estimated that over 90% of suspended particles in outdoor air have a particle size of less than 0.5 μm, accounting for less than 1% of the mass; particles larger than 1 μm account for less than 2% of the quantity but make up 97% of the mass.

Suspended particles in the air can be classified according to their activity as inert biological particles and biological particles. Non-biological particles are generated from the fragmentation, evaporation, combustion, or aggregation of solid or liquid matter. Biological particles mainly include bacteria, viruses, pollen, flower fluff, and down, and they represent a small proportion of suspended particles.

I. HVAC Air Filtration Classification

Air filtration is carried out at multiple locations within HVAC systems to ensure the required air cleanliness for the protection of production processes, users, and air handling equipment and ductwork. In HVAC systems, air filtration is generally divided into three stages: pre-filtration, intermediate filtration, and final filtration, achieved through different types of air filters.

Pre-filtration and intermediate filtration (primary and secondary filtration) are typically located at the points where outside air and recirculated air enter the air handling units. Filters should reach a certain efficiency to keep internal equipment (coils, fans) and air handling units relatively clean over an extended period, achieving the expected performance. Final filtration (tertiary filtration) is installed at the discharge section of the air handling unit or downstream (after airflow adjustment) to maintain duct cleanliness, extend the service life of terminal filters (if present), and protect personnel and workspaces from the hazards of suspended particles conveyed by the air handling unit when terminal filters are absent.

Terminal filtration devices installed around rooms, such as on ceilings or walls, can ensure the supply of the cleanest air, used to dilute or remove particles released within the room. The cleanliness of air leaving the filter depends on the filter structure and is related to the quantity and quality of the upstream air. Through proper design and correct configuration of air filters, the air quality and conditions required in pharmaceutical workshops can be achieved.

II. Working Principle of Air Filters

When air flows through a series of interconnected pore spaces forming a convoluted path within the microstructure of the filter (such as fibers or membranes), particles are captured in the filter media. The mechanisms by which filter media purifies air include interception, inertial effects, diffusion, electrostatic attraction, sieving, and gravitational deposition. The effectiveness of each mechanism in capturing particles primarily depends on particle size, air velocity, and the specifications of the filter structure (such as fiber diameter).

Interception effect:

When a particle of a certain size moves close to the surface of a fiber, if the distance from the particle center to the fiber surface is smaller than the particle radius, the dust particle will be intercepted by the filter fiber and deposited.

Inertial effect:

When the particle mass is large or the velocity is high, particles collide with the fiber surface due to inertia and are deposited.

Diffusion effect:

Small particles exhibit strong Brownian motion, making them more likely to collide with the fiber surface.

Electrostatic effect:

Fibers or particles may carry charges, creating an electrostatic attraction that draws particles to the fiber surface.

Sieving effect:

When the particle diameter is larger than the cross-sectional space between two fibers, the particle cannot pass through and is deposited.

Gravitational effect:

As particles pass through the fiber layer, they settle on the fibers due to gravity.

III. Filter Applications

The following provides an overview of primary to tertiary filtration and terminal filtration parameters.

A. Primary Filtration (Pre-filter)

Primary filtration has the lowest efficiency (and also the lowest cost) and is used for pre-filtration, capturing larger particles (diameter above 3 μm, such as insects or plant debris) frequently present in the external air. It also serves as a pre-filter to extend the life of secondary filtration units. It is recommended to use a G4 filter.

B. Secondary Filtration (Intermediate Filter)

This filter has a higher cost and is generally installed downstream of the primary filter to capture smaller particles (above 0.3 μm) in order to protect coil and fan units, ducts, and personnel in the air handling system. It is recommended to use an F7/8 filter.

C. Tertiary Filtration (Final Filter)

This type of filter is installed at the discharge section of the air handling unit, downstream of the primary and secondary filters as well as the fan/coil, and can use high-efficiency or HEPA filters.

High-efficiency filters: They can capture released mold and other substances (which may grow or accumulate on the condensate (wet) cooling coils) as well as dust on belts and similar surfaces. These filters prevent these substances from moving in the ducts and coming into contact with personnel. It is recommended to use F7/8 filters.

HEPA filters: Used when the conditioned space requires a cleanliness level of Class C (100,000), and no terminal filter is used; or to protect terminal filters and extend the service life of downstream HEPA filters. These filters should be equipped with seamless sealing gaskets or silicone seals on the downstream side to create a positive seal, preventing air from bypassing around the filter. Permanent upstream and downstream protective screens should be considered to prevent physical damage to the filter media. Each HEPA filter should be replaceable without interrupting the operation of adjacent filters. H12 (99.5%) to H14 (99.995%, MPPS) filters are recommended.

D. Terminal Filtration Structure

HEPA filters are generally used as terminal filters in cases where the cleanliness level is above Class 100,000 or when particles generated in the duct may contaminate the supply air. Terminal filters can also be used for recirculated/exhaust air.

These filters should have silicone seals on the downstream side to ensure a positive seal, preventing air from bypassing the filter edges. Permanent downstream protective screens (media protection devices) should be installed to prevent physical damage to the filter media. Each HEPA filter in the filter bank should be replaceable without disrupting the operation of adjacent filters. H13 (99.95%) to H14 (99.995%, MPPS) filters are recommended.

High-efficiency air diffusers can serve as terminal filtration units and be directly installed in the cleanroom suspended ceiling, suitable for various cleanliness levels and maintenance structures.

The main features include:

1. The diffuser housing is made of high-quality cold-rolled steel plate with an electrostatic plastic coated surface;

2. Ensures the airflow velocity for injection, preventing turbulence;

3. Strong versatility, simple construction, and low investment;

4. Compact structure with reliable sealing performance; air inlet can be from the side or top, and flanges are available in square or round shapes.

High-efficiency air diffusers are aesthetically pleasing, low in investment, have a simple box structure, and allow easy replacement of HEPA filters, making them the best choice for terminal purification equipment in cleanrooms.

Laminar flow hood is an air purification device that provides a localized high clean environment. It is mainly composed of a box, a fan, a primary air filter, a damping layer, a lamp, etc., and the shell is sprayed. The product can be both suspended and ground supported, compact and easy to use. It can be used as a single or with multiple connections to form a strip of clean area. There are two types of clean laminar flow hoods: inside the fan and external fan, and there are two installation methods: suspended type and floor bracket type. The clean laminar flow hood is to pass the air through the fan through a certain air pressure through the high-efficiency air filter, and then the damping layer equalizes the pressure to send the clean air into the working area in a vertical laminar flow type of airflow, so as to ensure that the working area achieves the high cleanliness required by the process. Compared with clean rooms, clean laminar flow hoods have the advantages of low investment, quick results, low requirements for plant civil construction, easy installation, and power saving. Bag-in-bag-out filters are filter housings that use one side to capture hazardous or toxic, biological, radioactive, cytotoxin, or carcinogenic substances. Prevents hazardous airborne substances from escaping from exhaust or return ducts. It is generally located around the room (near the floor) where the material is generated, but it can also be located in the middle. The biggest feature of the bag in and out filter is that the installation, replacement, and detection of the filter are all carried out under the protection of PVC bags (or high-temperature bags), and the filter unit is completely free of contact with the outside air, thus ensuring the safety of personnel and the environment, making the replacement process convenient and fast. To be precise, it is a modular end-air supply unit with self-powered and filtration effect.

FFU (fan filter unit) is divided into two types in shape, one is cuboid and the upper part is slope-shaped; The upper part of the FFU (fan filter unit) is sloped and acts as a diversion, which is conducive to the flow and even distribution of airflow. Rectangular FFU (fan filter unit) generally rely on a different way to equalize the airflow. Structurally, it is divided into two types, one is the whole and the other is split.

FFU (fan filter unit) is widely used in the following situations:  

1. Insufficient space for the ceiling of the clean room: In some occasions with high cleanliness requirements, the air supply static pressure box on the upper part of the ceiling of the clean room has a great role to balance the pressure on the cross-section of the clean room, but when the FFU (fan filter unit) is used, the ceiling of the clean room is divided into several modules, which can meet the pressure balance requirements of the air supply static pressure box on the upper part of the ceiling by adjusting each module (i.e., FFU (fan filter unit)), thus greatly reducing the height requirements of the static pressure box. In some retrofit projects, FFU (fan filter unit) effectively solves this problem when it is limited by floor height.

2. Insufficient static pressure in the clean room: In some renovation projects, due to the constraints of conditions, the air supply resistance is very large, and it is difficult to overcome the difficulty by relying on the air supply pressure of the air conditioning unit alone, which can be well solved due to the power of the FFU (fan filter unit).

3. Insufficient area of the air-conditioning room: In some renovation projects, due to the small area of the air-conditioning room, it is impossible to accommodate large air-conditioning units.This advantage is also applied to some situations with lower cleanliness requirements.

In modern large-scale cleanroom projects, the deployment scale of Fan Filter Unit (FFU) often reaches thousands. Faced with such a large number of devices, the traditional decentralized management model, which relies on manual on-site inspection and adjustment, not only has significant disadvantages in terms of labor costs and time efficiency, but also exhibits response lag and monitoring blind spots when dealing with sudden equipment anomalies. The introduction of the Fan Filter Unit (FFU) network group control system fundamentally restructures this management paradigm, realizing centralized and intelligent control of massive amounts of equipment.

I. Fault Alarm: Constructing an all-weather, blind-spot-free intelligent monitoring system

In operating environments lacking centralized monitoring, damage to the motor or abnormal shutdown of a single Fan Filter Unit (FFU) is often difficult to detect in a timely manner, typically only emerging during periodic manual inspections. During this lag period, the cleanliness parameters of the local microenvironment may deviate, posing a potential risk to high-precision manufacturing processes and even leading to the scrapping of batches of products.

After deploying the Fan Filter Unit (FFU) network control system, all devices are connected to the unified network as intelligent nodes. The system's built-in fault self-diagnosis module monitors the operating status of each Fan Filter Unit (FFU) in real time at the millisecond level. Once a device experiences overload, phase loss, abnormal shutdown, or sensor malfunction, the system will immediately trigger a tiered alarm on the central control platform and simultaneously notify maintenance personnel through audible and visual alerts and remote communication. This instant feedback mechanism effectively prevents the spread of single-point failures to systemic risks, ensuring the continuous stability and compliance of the clean environment.

II. Remote speed control: Enables flexible and precise adjustment of wind speed parameters

Cleanroom production processes are dynamically adjustable, with varying requirements for airflow organization and cleanliness levels at different stages. Traditional adjustment methods require maintenance personnel to climb to heights and adjust equipment dials or knobs one by one, which is not only physically demanding but also carries the risk of misoperation and cannot meet the needs of modern factories for rapid line changeovers and process modifications.

Through the Fan Filter Unit (FFU) network control system, managers can remotely adjust the speed of any single unit, a specific area, or all equipment from the central control room. The system supports multi-level presets and strategic command issuance, and can synchronize the speed of thousands of devices with a single click based on production plans or environmental monitoring data. This remote and precise control capability not only significantly reduces the workload of maintenance personnel but also gives the cleanroom environment the flexibility to adapt to changing needs, effectively supporting the rapid iteration and optimization of production processes.

III. Centralized Management: Building a Highly Integrated Digital Operation and Maintenance Platform

Despite the low-maintenance nature of Fan Filter Unit (FFU), in the absence of effective management tools, maintenance teams still need to expend considerable effort on data collection, report preparation, and fault tracing when dealing with large equipment assets. Furthermore, if subsystems such as HVAC and lighting are independent, it will lead to fragmented management interfaces, increasing the complexity of system coordination.

The FFU (Functional Unit) network control system integrates dispersed hardware resources into a unified digital management platform. The system possesses comprehensive data mining and analysis capabilities, automatically generating equipment operation logs, energy consumption analysis reports, and fault statistics charts, providing objective data support for management decisions. Simultaneously, the system supports deep integration with building automation systems or manufacturing execution systems, achieving cross-system logical linkage. For example, it can automatically adjust airflow based on occupancy status to achieve energy savings, or execute emergency shutdown upon receiving a fire alarm signal. This highly integrated intelligent architecture significantly improves operational efficiency and reduces total lifecycle operating costs.

In summary, the Fan Filter Unit (FFU) network group control system, with its intelligent advantages in fault early warning, remote control and centralized management, upgrades cleanroom operation and maintenance from an inefficient, labor-intensive model to a highly efficient, digitally driven model, truly enabling a single person to accurately control thousands of devices.

What is Plant Tissue Culture lab and a Tissue Culture Laboratory?

1. What is plant tissue culture?

Plant tissue culture is a technique in which excised plant organs, tissues, cells, or protoplasts are cultivated under sterile and artificially controlled environmental conditions using appropriate culture media, allowing them to regenerate cells, tissues, or complete plants. The basis of plant tissue culture is the 'totipotency' of plant cells, meaning that each cell possesses the ability to replicate like Sun Wukong's clones.

Plant tissue culture provides an efficient, convenient, and controllable method for plant production and research. With continuous technological development, it has been widely applied in the conservation of germplasm resources, plant breeding, production of plant secondary metabolites, and plant genetic engineering, achieving remarkable and substantial results.

Through plant tissue culture, a single plant can be propagated into thousands or even tens of thousands of tissue-cultured seedlings. It enables the mass production of clones, preserves superior traits, shortens production cycles, and provides abundant material security for our lives. It has now become the most active and widely applied technology in modern biotechnology.

2. What is a tissue culture laboratory?

A plant tissue culture laboratory is a specialized facility for conducting plant tissue culture experiments. Through plant tissue culture techniques, it is possible to artificially control environmental conditions in the laboratory, simulating the growth processes of plants in nature, thereby achieving goals such as rapid propagation, variety improvement, and genetic transformation.

Plant tissue culture is carried out under strictly sterile conditions, so it requires equipment such as a Clean Bench, electronic analytical balance, precision pipette, autoclave, stereomicroscope, light-incubation chamber, biochemical incubator, air conditioner, and refrigerator.

How to Properly Choose a Clean Bench? 

How to Properly Choose a Clean Bench?

A Clean Bench is a purification device that provides a locally high-cleanliness working environment with strong versatility. Selecting a good Clean Bench is the first step to ensure sterile operations. It not only provides a sterile environment for laboratory personnel but also effectively prevents cross-contamination, allowing instruments to better serve as facilitators for experiments.

Clean Benches can be divided Horizontal Flow and Vertical Flow types based on airflow patterns. Horizontal laminar flow clean bench offer an open operation space, while vertica flow workbenches typically come with movable glass front windows. Users can choose according to their needs.

High-quality materials and scientific design are the first steps toward sterile culture. Clean Benches should use high-quality steel plates with electrostatic powder coating, and the work surface should be made entirely of stainless steel 304. The work area should be equipped with LED lighting and a UV sterilization system, built-in backup waterproof sockets, and optional glass side windows for easy observation. Options are available for single or dual-person operation.

Creating a high-cleanliness working environment and a Class 100 clean space is the core function of a Clean Bench as a key device for sterile operations. It should include a built-in adjustable air volume fan system, horizontal or vertical uniform airflow, and a high-efficiency filter made of ultra-fine glass fiber paper, achieving a filtration efficiency of ≥99.99% (@0.3μm).

High safety performance standards are an important guarantee for sterile culture. The workbench should include built-in mechanical protection devices, interlocks for lighting and sterilization systems, and the sterilization system can only be activated when the sliding door is fully closed. When the UV lamp is on, opening the movable front window will automatically turn off the UV lamp. Optional delayed switches and programmed timing functions for the sterilization system improve efficiency while ensuring user safety.

A user-friendly interface is the choice for digital upgrades and better empowers sterile operations. The standard controller comes with an embedded LCD display that can show the device's operating status in real time, such as wind speed, lighting, sterilization, and filter lifespan, and provides multiple audible and visual alarm functions for various faults.

In the ICU wards of hospitals, negative pressure control is a crucial technology, acting as an invisible barrier to protect the safety of medical staff and patients. Behind this barrier, the seamless coordination of efficient air supply and exhaust systems, along with sealing mechanisms to prevent virus leakage , together enact a battle between technology and the virus.

The principle of negative pressure control

The core principle of a negative pressure environment is to maintain an indoor air pressure lower than that of adjacent areas. When the ward door is closed, air automatically flows from the corridor (positive pressure zone) to the ward (negative pressure zone) due to the pressure difference, while contaminated air inside the ward cannot escape. This tiny pressure difference (usually -5Pa to -15Pa), though imperceptible, can effectively curb the spread of viruses .

High-efficiency air supply outlets and exhaust systems working together

In negative pressure wards, HEPA Box and exhaust systems play different roles, but together they maintain the stability of the negative pressure environment.

• HEPA Box : These are responsible for delivering fresh air that has undergone three stages of filtration—coarse, medium, and high efficiency—into the patient rooms. This fresh air is purified at each stage before entering the rooms, ensuring the cleanliness of the supplied air. The air supply outlets are typically located at the top of the room, allowing clean air to flow first through the breathing area of medical staff, then through the patient area, and finally be captured by the exhaust vents.

• Exhaust system : It is the "heart" of the negative pressure environment. The exhaust fan runs continuously, drawing out contaminated air from the ward and discharging it at high altitude after high-efficiency filtration and disinfection. The exhaust vents are usually located near the head of the bed for convenient and rapid removal of contaminated air.

This "upward delivery and downward exhaust" airflow organization method creates a directional airflow, which allows polluted air to be quickly captured and discharged after it is generated, avoiding its stagnation and spread in the ward.

Sealing logic to prevent virus leakage

The ingenious "reverse application" of high-efficiency air outlets lies in the fact that they don't simply "send air," but rather, through precise control of the airflow, work in conjunction with the exhaust system to construct a tightly sealed system. The logic behind this system is:

• Airflow balance : The exhaust air volume must always be greater than the supply air volume; this is fundamental to maintaining negative pressure. By precisely adjusting the airflow of the supply and exhaust fans, the ward is kept under negative pressure at all times.

• High-efficiency filtration : Both the supply and exhaust air undergo high-efficiency filtration. The three-stage filtration of the supply air ensures that the air entering the ward is clean; the high-efficiency filtration of the exhaust air ensures that the exhausted air will not become a new source of pollution.

• Pressure gradient : The pressure difference decreases sequentially from the clean area to the potentially contaminated area and then to the contaminated area, forming a gradient. This gradient design ensures that airflow will move from the clean area to the contaminated area even when doors are open, thus preventing cross-infection.

The negative pressure control system in hospital ICU wards is a perfect combination of modern medicine and engineering technology. The precise coordination of high-efficiency air supply outlets and exhaust systems, along with the sealing logic behind them, together form a solid defense, providing strong technical support for combating infectious diseases.

Clean air plays a crucial role in plant tissue culture and pharmaceutical technology development, and is the core foundation for ensuring experimental success, product quality, and production safety. Although the application scenarios in the two fields are different, their core logic is the same: maintaining a sterile or controlled environment by controlling airborne microbial and particulate pollution.

Here's a breakdown of the role of clean air in these two key areas:

Ⅰ. The key role in plant tissue culture

Plant tissue culture is a technology in which plant explants (such as stem tips, leaves, etc.) are inoculated into artificially prepared medium for culture under sterile conditions. Clean air is the first line of defense against pollution.

1. Reduce microbial contamination rate (core pain point)

The current situation is grim: According to statistics, the microbial contamination rate in plant tissue culture is as high as 15%-40%, of which bacterial contamination accounts for about 80%, followed by fungal contamination. Once contaminated, it will not only lead to the scrapping of the current batch of seedlings, but may also spread to the entire culture room, causing huge economic losses.

Airborne pollution: Airborne fungal spores (e.g., Penicillium, Aspergillus niger) and bacterial spores are the main sources of pollution. If these particles settle on the medium or explant incision, they will multiply rapidly at the right temperature and humidity.

The role of clean air:Blocking the transmission pathway: The high-efficiency air filtration system (HEPA or ULPA) removes particulate matter ≥ 0.3 μm in the air, directly cutting off the aerosol transmission path of fungal spores and bacteria.

Laminar flow clean bench efficiency: In inoculation operations, laminar flow clean benches rely on clean laminar air to form an "air barrier" to protect the operating area from external environmental interference. If the air intake is not clean, even if the wind speed reaches the standard, the sterility effect cannot be guaranteed.

2. Ensure the growth quality and genetic stability of tissue culture seedlings

Hidden pollution prevention and control: Some endophytes or low-concentration microorganisms may not immediately cause turbidity of the culture medium, but they will secrete toxins or compete for nutrients, inhibit plant cell division and differentiation, and lead to slow growth, deformity and even death of tissue culture seedlings. Clean air minimizes this hidden pollution.

Reliability of experimental data: In scientific research experiments, variable interference caused by air pollution can make experimental results irreproducible. The clean environment ensures the accuracy of experimental results, which is especially critical for genetic improvement and genetic engineering research.

3. Optimize environmental control strategies

Dynamic sterility demand: Traditional UV or ozone disinfection has "human-machine separation" limitations and cannot sustain bacterial inhibition. Modern tissue culture rooms are more inclined to use air purification equipment with human-machine coexistence functions to achieve 24-hour planktonic bacteria and settled bacteria to meet the standards and ensure continuous cleanliness.

Ⅱ. The Key Role in Pharmaceutical Technology Development

In the pharmaceutical field, clean air is not only a guarantee for the success of experiments but also a mandatory requirement under laws and regulations (such as GMP), directly affecting drug safety and patient health.

1. Compliance with GMP (Good Manufacturing Practice for Pharmaceutical Products)

Regulatory Requirement: GMP standards worldwide (such as China GMP, EU GMP, and US FDA cGMP) strictly classify the cleanliness of the air in pharmaceutical environments (e.g., Grade A, B, C, D).

Key Indicators: The number of suspended particles and microbiological limits (airborne microorganisms, settled bacteria, surface microorganisms) in the air must be strictly controlled. For example, in aseptic filling areas (Grade A), the number of particles ≥0.5 μm per cubic meter must not exceed 3,520, and no microorganisms should be detected.

2. Ensuring the Safety of Aseptic Preparations

Protection of High-Risk Operations: During the production of aseptic drugs such as injections, vaccines, biological products, and ophthalmic preparations, any airborne particles or microorganisms entering the product may cause severe infection risks or even death.

Prevention of Cross-Contamination: When developing and producing drugs with different active pharmaceutical ingredients (APIs), clean air conditioning systems (HVAC) control air pressure differences and directional airflow to prevent high-activity or sensitizing substances from spreading through the air to other areas, thereby avoiding cross-contamination.

3. Supporting Biotechnology and Cell Therapy Development

Sensitivity of Cell Cultures: In the development of monoclonal antibodies, gene therapy vectors (such as viral vectors), and stem cell therapies, cells are extremely sensitive to the environment. Contamination of cell banks by mycoplasma, viruses, or fungal spores in the air can lead to the failure of an entire R&D project, resulting in losses of millions of dollars.

Process Stability: A clean air environment helps maintain the stability of the surroundings of bioreactors, reducing abnormal cell metabolism due to environmental fluctuations and ensuring batch-to-batch consistency of drugs.

4. Extending Equipment Lifespan and Reducing Downtime

Clean air reduces dust particle deposition inside precision instruments (such as filling machines, lyophilizers, and testing equipment), lowers equipment failure rates, decreases the frequency of cleaning and maintenance, and thereby enhances production efficiency.

Clean air is the lifeline of plant tissue culture and pharmaceutical technology development. In plant tissue culture, it is a key technical means to reduce costs and increase propagation coefficients. In pharmaceutical development, it is the legal baseline for compliant production and safeguarding human health. With technological advancements, the shift from traditional static disinfection to dynamic, real-time, human-machine interactive intelligent air purification solutions has become a common trend for improving competitiveness in both industries.

In the construction and maintenance of clean rooms, operating rooms or precision electronics workshops, high-efficiency filters (HEPA/ULPA) are undoubtedly the heart of existence. They are expensive, often thousands or even tens of thousands of yuan a piece, and are the last line of defense to ensure environmental cleanliness. However, many managers often only focus on the installation and replacement of filters, but ignore their state before "work" - storage.

Randomly stacking expensive high-efficiency filters in the corners of damp, cold warehouses is tantamount to a "death sentence" before they are put into use. This will not only lead to moisture and mold in the filter media and aging of seals, but may also cause leaks after installation, causing huge economic losses and safety hazards. Today, we're going to talk about two of the deadliest and most overlooked details of HEPA storage: moisture-proof packaging and vertical placement.

I. Moisture-proof packaging: the "golden bell" that guards the filter element

The core filter material of a HEPA filter is usually ultra-fine fiberglass paper, which is extremely hygroscopic. Once damp, not only will the filtration efficiency plummet, but what is even more frightening is that it will become a breeding ground for bacteria and mold. During cleanroom operation, these mold spores will spread with the airflow, causing serious secondary pollution.

Therefore, the original packaging is the best umbrella for filters.

1. Keep the factory seal:

The vast majority of high-efficiency filters produced by regular manufacturers will be sealed and packaged in plastic bags when they leave the factory, and are equipped with moisture-proof paper or cardboard corner guards. As long as the filter is not installed, this layer of packaging must not be removed. This layer of packaging is not only dustproof, but also a barrier to moisture in the air.

2. Secondary protection:

If you are in a warehouse with high humidity, the original packaging alone may not be enough. It is recommended to cover the original packaging with a thick PE plastic bag and put an appropriate amount of color-changing silicone desiccant.

3. Inspection of damage:

During the handling or inspection process, if the outer packaging is found to be damaged, the inside of the filter must be checked immediately. If there are signs of moisture, the performance must be re-tested and never installed directly.

Remember, don't let the filter "run naked". Any exposure to humid air is an overdraft filter life.

II. Vertical placement: avoid irreversible physical damage

In addition to moisture resistance, the posture of the filter is also a matter of life and death. In order to save space, many warehouses are accustomed to stacking filters flat like books, or leaning against the wall at will, which is extremely wrong.

The HEPA filter must be placed vertically (upright).

1. Prevent filter media deformation:

The filter paper of high-efficiency filters is very delicate and folded. If stacked flat for a long time, the filter at the bottom will be subjected to tremendous pressure, causing the filter paper to deform or even break. Once the filter paper is damaged, its filtration efficiency will be reduced to zero, and the damage is irreparable.

2. Avoid damage to the sealant:

The filter border is often coated with a sealant (such as polyurethane or silicone). Long-term flat pressure will cause plastic deformation of the sealant, and it cannot fit closely with the ceiling or equipment during installation, resulting in gaps and air leakage.

3. Stacking Height Limitations:

Even when placed vertically, stacking cannot be done indefinitely. Generally, the stacking height should not exceed 2 meters (or follow the indications on the packaging box). Excessive stacking not only increases the risk of tipping over, but the filters at the bottom are also prone to frame damage due to excessive pressure.

The correct practice is: place the filters upright on pallets or shelves, following the direction indicated by the “up” arrows on the packaging box. If conditions allow, it is best to use dedicated racks to prevent direct contact with the ground, further isolating the filters from ground moisture.

III. Environmental Control and “First In, First Out”

In addition to the above points, the choice of storage environment is also crucial.

• Temperature and humidity control:

The ideal storage temperature should be between 0℃ and 40℃, and the relative humidity should preferably be kept below 60%. Avoid storing filters in places with drastic temperature changes to prevent condensation.

• Keep away from sources of contamination:

Warehouses should be kept clean, away from acidic or alkaline chemicals, dust sources, and corrosive gases.

• First In, First Out principle:

High-efficiency filters also have a “shelf life.” It is generally recommended that storage should not exceed one year (for filters with adhesive seals, it is even suggested not to exceed two months). Therefore, when using the filters, it is essential to follow the “first in, first out” principle, giving priority to products with earlier storage dates to avoid inventory accumulation leading to expiration and ineffectiveness.

High-efficiency filters are sophisticated industrial products, not simple construction materials. By handling them with extra care, you ensure greater security for your project. Do not let your high-value filters deteriorate prematurely in a damp, dark warehouse. Use proper moisture-proof packaging, maintain vertical placement, and ensure that each filter can operate at its optimal condition to protect clean spaces.

In the hallowed halls of modern medicine, clean operating rooms are the last physical barrier protecting patients' lives. While we marvel at the advanced surgical techniques, we often overlook the air purification system that works tirelessly day and night overhead. This system is like the "respiratory system" of the operating room, and its core component---the air filter---is the "invisible defense" against bacteria and dust.

Primary filter: The vanguard in the battle.

The primary filter (pre-filter) is the first line of defense in an air purification system, typically installed at the fresh air inlet or mixing section of an air handling unit (AHU). Its role is like that of a strong and capable "vanguard," responsible for intercepting those visible "large" enemies in the air.

These filters are primarily made of non-woven fabric (synthetic fiber), metal mesh (stainless steel mesh), or nylon mesh, and have a relatively coarse structure. Their main task is to capture particles larger than 5 micrometers in diameter, such as airborne hair, lint, pollen, and large dust particles. Without the effective interception of the primary filter, these impurities will quickly clog subsequent, more sophisticated filtration devices. Therefore, primary filters require the most frequent maintenance, typically needing to be replaced every 1 to 2 months, or cleaned promptly when dust accumulation is severe to ensure sufficient fresh airflow.

Medium-efficiency filter: the "backbone" bridging the gap between upstream and downstream applications.

Although the air that has passed through the primary filter removes large particles, it still contains many fine dust particles and microorganisms. This is where the medium-efficiency filter (medium filter) comes in. Located after the primary filter and before the high-efficiency filter, it plays a crucial role in bridging the gap between the two.

Medium-efficiency filters typically employ a bag-type structure (pocket filter), filled internally with glass fiber or synthetic fiber, with a denser fiber arrangement. They effectively capture particles with diameters between 1 and 5 micrometers, such as fine dust, smoke, and some bacterial carriers. As the "backbone" of the system, medium-efficiency filters not only further purify the air, but more importantly, they protect the expensive high-efficiency filters at the end, preventing premature clogging. Generally, medium-efficiency filters should be replaced every 3 to 6 months, making them a crucial element in maintaining stable system operation.

High-efficiency air filters (HEPA) filters: the ultimate gatekeeper for victory.

If the first two stages of filtration are the foundation, then the high-efficiency air filters (HEPA ) is the "ultimate arbiter" of air quality in a clean operating room. It is usually installed at the air supply terminal in the ceiling of the operating room (ceiling HEPA) and is the last barrier before the air enters the surgical area.

HEPA filters are made of countless extremely fine glass fibers folded together, forming intricate nanoscale channels. They boast a filtration efficiency of over 99.97% for particles with a diameter of 0.3 micrometers or larger (including the vast majority of bacteria, viruses, and dust). This barrier ensures that the air delivered to the operating table is nearly sterile, significantly reducing the risk of postoperative infection. HEPA filters have a long lifespan, typically lasting more than 3 years, but require regular resistance testing (pressure drop test). Once the resistance exceeds 160% of the initial resistance, the filter must be replaced immediately.

Sub-HEPA filters: "Elite guardians" for specific scenarios.

In areas where cleanliness requirements are slightly lower than Class 100 or Class 1000 operating rooms, or as a pre-filter for HEPA systems, Sub-HEPA filters (Sub high efficiency air filter) play a unique role. Their filtration efficiency falls between medium and high efficiency, primarily targeting particles larger than 0.5 micrometers in diameter, with filtration efficiencies ranging from 95% to 99.9%.

Sub-HEPA filters are compact in structure and have moderate resistance, and are commonly used in Class III and IV clean operating rooms or clean auxiliary rooms. Like an "elite guardian," while not as stringent as HEPA filters, they are sufficient to meet the aseptic requirements of general surgeries. They are also often used as pre-filters in HEPA systems to further extend the lifespan of the final filter.

From the coarse primary filter to the precise HEPA filter, these four stages of filters work in tandem to construct a comprehensive air purification network. Though hidden in ceilings and machine rooms, working silently, they are an indispensable cornerstone of the modern medical safety system. Regular maintenance and scientific management of these "invisible defenses" safeguard the life and health of every patient.

In recent years, with the rapid development of the new energy electric vehicle industry, lithium batteries, as the core power source, have seen continuously increasing production demand, which in turn has driven the large-scale expansion of battery manufacturing enterprises and significantly heightened the demand for high-standard lithium battery cleanroom construction.

An in-depth analysis of the key technical points in the construction of new energy lithium battery cleanrooms:

01 Division of Clean Areas in Lithium Battery Cleanrooms
Cleanrooms are usually divided into different grade areas according to cleanliness requirements to achieve precise control over airborne particles, microorganisms, and other contaminants.
Clean Area: This area has the strictest requirements for air quality, particle concentration, and microbial count. High-efficiency air filters (HEPA or ULPA) must be used, positive pressure (or negative pressure under specific process requirements) must be maintained, and personnel are required to wear protective clothing such as cleanroom suits.
Semi-Clean Area: The cleanliness standard is slightly lower than that of the clean area but still requires effective control of airborne particles and microorganisms. Generally, high-efficiency air filtration systems are installed and personnel are required to wear cleanroom suits.
Partially Clean Area: The control over particle counts is relatively relaxed but still needs to remain within the acceptable range for the process. Standard air filters with basic cleanroom attire are usually sufficient.
Non-Clean Area: The cleanliness requirements are the lowest, with no special air filtration equipment or professional cleanroom clothing needed. This area is mainly used for auxiliary or non-critical work areas.

02. Lithium Battery Cleanroom Air Conditioning Treatment System
To ensure the stability and cleanliness of the production environment, the cleanroom must be equipped with a comprehensive air treatment system, including air purification devices, supply and return air equipment, and temperature and humidity control systems. Among them, air purification equipment generally uses High-Efficiency (HEPA) or Ultra-Low Penetration Air (ULPA) filters, which can efficiently remove airborne particles, microorganisms, and harmful gases; the fans and air conditioning systems work in coordination to ensure that the temperature, humidity, and airflow organization in the cleanroom always remain at the optimal state required by the process.

03 Interior Installation of Lithium Battery Cleanrooms
The interior finishing materials of cleanrooms need to balance functionality with cleanliness maintenance requirements, focusing on ease of cleaning, anti-static performance, and corrosion resistance.
Flooring Materials: Common choices include conductive floors, anti-static epoxy floors, or high-durability anti-static PVC floors, which can effectively dissipate static electricity and facilitate routine cleaning.
Wall Materials: It is recommended to use stainless steel panels, acid- and alkali-resistant coatings, or other corrosion-resistant, smooth, seamless finishing materials to minimize dust accumulation in corners.
Special Function Areas: High-temperature rooms are usually independently isolated, with enclosures made of rock wool sandwich panels and doors equipped with fireproof doors. Low-humidity areas use rock wool partition walls and glass magnesium rock wool ceilings, paired with sealed molded doors and double-layer vacuum glass windows to enhance sealing and thermal insulation performance.

04 Lithium Battery Cleanroom Lighting System

Lighting design should take into account functionality, cleanliness, and energy efficiency:
The workshop should provide a uniform and bright lighting environment to avoid shadows that may interfere with precision operations;Lighting fixtures must be designed to be dust-free, with smooth surfaces and no seams, to prevent dust adhesion and accumulation;
High-energy-efficiency LED fixtures should be preferred, significantly reducing energy consumption and operation and maintenance costs while ensuring adequate illumination.

05 Personnel Movement and Protective Measures in Lithium Battery Cleanrooms
Personnel are one of the main sources of contamination in cleanrooms; therefore, it is essential to scientifically plan pedestrian flow channels and implement strict access management and behavioral standards:
Establish reasonable changing rooms, air showers, and buffer zones to achieve effective separation of personnel flow and material flow;
All personnel entering the clean area must receive professional training to master cleanroom behavioral guidelines, protective equipment wearing standards, and emergency response procedures;
Through institutionalized management and regular assessments, continuously enhance employees' awareness of cleanliness and operational proficiency, ensuring the cleanliness and stability of the production environment from the source.

Walking into a modern semiconductor wafer fabrication plant or a high-end biopharmaceutical workshop, one is greeted by fully equipped engineers, precisely maneuvering robotic arms, and an almost 'vacuum-like' clean environment. The low hum of the air purification system seems to tell a story of humanity's relentless pursuit of absolute cleanliness. This is the cleanroom—the cornerstone of modern high-end manufacturing.

Cleanroom: A Micron-Level Industrial Fortress

A cleanroom, also known as a controlled environment room, is not simply a room that is cleaned physically, but a controlled environment created through precise engineering methods. Its core lies in controlling airborne dust particles, microorganisms, harmful gases, and other contaminants to extremely low concentration levels to meet the stringent requirements of specific manufacturing processes.

• Micron-level cleanliness standards: The cleanliness of a cleanroom follows international standards (such as ISO 14644-1), with levels ranging from ISO Class 1 (highest) to ISO Class 9. For example, in an ISO Class 5 cleanroom (equivalent to the former "Class 100" standard), the number of particles larger than 0.5 microns per cubic meter of air must not exceed 3,520. In contrast, the quantity of particles in the air of an ordinary urban environment can reach several million. In the field of chip manufacturing, when line widths enter the 3-nanometer era, even the tiniest dust particle can become a "lethal killer" causing product defects.

• Comprehensive control beyond cleanliness: In addition to particulate matter, a cleanroom must precisely control temperature, humidity, pressure differential, static electricity, and even vibration. For instance, semiconductor photolithography areas require temperature fluctuations to be controlled within ±0.1°C to prevent misalignment caused by thermal expansion and contraction; simultaneously, maintaining positive pressure inside the cleanroom can effectively prevent unfiltered dirty air from entering.

Core of the Design: Building a "Zero-Pollution" Ecosystem

The design goal of a cleanroom goes far beyond simply "filtering the air"; it is about creating a dynamic ecosystem capable of continuously resisting and eliminating contamination. The core design principles are reflected in the following aspects:

• The Art of Airflow Organization: Airflow is the "blood" of a cleanroom. Designers use Computational Fluid Dynamics (CFD) simulations to optimize airflow paths, ensuring that clean air evenly "washes" the entire work area and rapidly removes contaminants. In the highest-grade clean areas, vertical unidirectional (laminar) flow is typically used, with clean air flowing from top to bottom like an "air piston" to remove pollutants with maximum efficiency.

• Sealing of Building Structures: The walls, ceilings, and floors of the workshop form the "skin" of the clean space. All materials must be smooth, non-dusting, dust-resistant, and corrosion-resistant, such as color steel panels, stainless steel sheets, and epoxy self-leveling floors. All joints require rounded treatments and reliable sealing, and all pipelines must be concealed to eliminate any dead corners where dirt could accumulate.

• Intelligent Dynamic Monitoring: Modern cleanrooms are a "smart living entity." By deploying laser particle counters, temperature and humidity sensors, and differential pressure meters, combined with a Building Management System (BMS), real-time 24/7 monitoring and automatic adjustment of environmental parameters can be achieved, ensuring that any minor anomalies are detected and addressed immediately.

Core Weapon: The 'Skynet' Built by Multi-Stage Filtration Equipment

The key to achieving ultimate purification lies in a meticulously coordinated filtration equipment system, which functions like the 'super lungs' of a workshop, providing multiple layers of protection to ensure clean air.

• Primary and Medium Efficiency Filters (Pre-Filtration): This is the first line of defense in an air purification system. The primary filter (such as G4 grade) intercepts large particles above 5 microns, including dust and hair; the medium efficiency filter (such as F8 grade) further captures medium particles between 1–5 microns. Their main purpose is to protect the terminal high-efficiency filters and extend their service life.

• High-Efficiency/Ultra-High-Efficiency Filters (HEPA/ULPA): This is the 'heart' of a cleanroom. High-Efficiency Particulate Air (HEPA) filters can capture 99.97% of particles as small as 0.3 microns, while the more advanced Ultra-Low Penetration Air (ULPA) filters can capture even smaller particles. Installed at the end of the air supply system (such as in Fan Filter Unit (FFU), they are the final assurance that the air delivered to the cleanroom meets the required cleanliness level.

• Chemical Filters (AMC Control): In cutting-edge industries like semiconductors, controlling only particulate matter is far from sufficient. Gaseous molecular pollutants (AMC), such as acids and bases generated during processing, are equally critical. Chemical filters filled with activated carbon or other specialized media selectively adsorb these molecular-level pollutants, providing more comprehensive protection for the production process.

When air is purified to its extreme, it is no longer ordinary air but a special medium that carries the highest precision and strictest standards of modern industry. From the smartphones in our hands to life-saving vaccines, cleanrooms, with their 'invisible precision,' silently support the 'visible heights' of human technological civilization.