In the laboratory air quality assurance system, medium-efficiency bag filters are the core pretreatment link of the air purification system. They are mainly used to intercept intermittent particulate pollutants in the air, protect the high-efficiency filters at the back end, and maintain the cleanliness of the experimental environment. Its application needs to be combined with the type of laboratory, pollution characteristics and the design logic of the purification system, as follows:
I. The Core Role of Medium-Efficiency Bag Filters in Laboratories
Laboratory air pollutants are complex (such as dust, chemical aerosols, biological particles, etc.). The core value of medium-efficiency bag filters lies in “bridging the gap”, filling the filtration gap between primary filters (intercepting large particles ≥5μm) and high-efficiency filters (intercepting tiny particles ≥0.3μm).
| Dimension of function | Specific explanation | The significance of the laboratory scene |
| Protect the back-end devices | Intercept 80% to 95% of 1-5μm particles (such as dust, pollen, and fiber debris) to prevent them from clogging the high-efficiency filter or damaging the heat exchanger of the air conditioning unit | Extend the service life of high-efficiency filters (reduce replacement frequency and maintenance costs) to ensure the stable operation of the air conditioning system |
| Control particulate pollution | Reduce the suspended particles entering the laboratory to lower the interference with precise experiments (such as microscopic observation and semiconductor material experiments) | Avoid particle adhesion that may affect the purity of the experimental sample or the detection accuracy of the instrument |
| Auxiliary purification |
Combined with a “three-stage filtration” system of primary and high-efficiency filtration, it provides basic cleanliness for biosafety laboratories, clean laboratories, etc |
Meet the pretreatment requirements for air purification stipulated in the “General Requirements for Laboratory Biosafety” (GB 19489) |
Ii. Key Parameters for Selecting Medium-Efficiency Bag Filters in the Laboratory
The laboratory should select the proper model based on its pollution load and cleanliness requirements. Key parameters include: 1. Filtration efficiency grade (core indicator)
In accordance with the international standard EN 779:2012 or the national standard GB/T 14295-2019, common laboratory grades and applicable scenarios:
F5-F6 grade (Medium efficiency 1-2 grade) : Filtration efficiency 40%-80% (for 1μm particles), suitable for general chemical laboratories, sample pretreatment rooms and other areas with relatively light pollution, serving as basic pretreatment.
F7-F8 grade (medium efficiency 3-4 grade) : Filtration efficiency 80%-95% (for 1μm particles), suitable for biosafety level 2 laboratories, microbiological culture rooms, precision instrument rooms, and scenarios requiring higher pretreatment accuracy.
F9 grade (Near High Efficiency) : Filtration efficiency ≥95% (for 1μm particles), suitable for laboratories with cleanliness requirements close to Class 100 (such as cell rooms, photolithography laboratories), can reduce the load on high-efficiency filters.
2. Other key parameters
Filter material: Commonly used are glass fiber, polyester fiber (polyester), and polypropylene fiber. Polyester fibers are preferred in the laboratory – they are resistant to chemical corrosion (can withstand a small amount of acid and alkali aerosols), have a high dust holding capacity, and are easy to clean (some can be reused).
Number of bags and size: The more bags there are (such as 3 bags, 5 bags, 7 bags), the larger the effective filtration area, the lower the resistance and the higher the dust holding capacity. It needs to be matched according to the air supply volume of the air conditioner (for example, if the air volume is 1000m³/h, a 5-bag type can be selected, with dimensions of 592×592×292mm).
Initial resistance: The conventional range is 40-80Pa (at air volume). Excessively high resistance will increase the energy consumption of the air conditioner. It is recommended to choose a low-resistance type (such as ≤60Pa).
Dust holding capacity: The weight of particles that the filter material can carry per unit area (such as ≥400g/m²). The higher the dust holding capacity, the longer the replacement cycle.
Iii. Laboratory Application Scenarios and Adaptation Suggestions
The demand for air purification varies significantly among different types of laboratories. The selection of medium-efficiency bag filters should be “matched as needed”
| Laboratory type | Main pollutants | Recommended filtering level | Special requirements |
| General Chemistry Laboratory | Dust, a small amount of chemical volatile substances (non-corrosive) | Grade F5-F6 | The filter material should be resistant to mild organic solvents. It is recommended to use it in combination with an activated carbon filter |
| Biosafety Laboratory (BSL-2/3) | Microbial aerosols (bacteria, viruses), and hair from experimental animals | Grade F7-F8 | It needs to be combined with the primary filter (G4 grade) to form a “primary + secondary” pretreatment, and a high-efficiency filter (HEPA) is connected in series at the back end. |
| Precision instrument laboratory (such as ICP-MS, electron microscope) | Ultrafine dust, fibers, and electrostatically adsorbed particles | F8-F9 levels | Select low-resistance and low-dust-generating filter materials (to avoid self-shedding of fibers), and it is recommended to install static electricity elimination devices |
| Clean laboratories (such as pharmaceutical research and development, semiconductors) | Micron-sized dust and suspended particles | F9 level (Near High Efficiency) | It needs to meet the ISO 8-7 grade cleanliness requirements and form a “medium efficiency + high efficiency” two-stage filtration with high-efficiency filters |
| Sample pretreatment chamber | Dust from sample grinding and residual particles of reagents | Grade F6-F7 | The dust holding capacity should be ≥500g/m², and it is suitable for high air volume systems (to avoid dust accumulation). |
Iv. Core Precautions for Installation and Maintenance
The air purification effect in the laboratory depends on “correct installation + standardized maintenance”. For medium-efficiency bag filters, the following key points need to be focused on:
1. Installation specifications
System location: It must be installed in the air supply section of the air conditioning unit (after the primary filter and before the high-efficiency filter) to prevent unfiltered air from bypassing the filter (the frame seal needs to be checked, with the gap ≤0.1mm).
Airflow direction: Install strictly in accordance with the “airflow arrow” on the filter bag (the fluffy side of the filter material should face the airflow). Reverse installation will cause a sudden increase in resistance and a decrease in filtration efficiency.
Spacing reservation: A spacing of 5 to 10cm should be reserved between the filter bags to ensure uniform air flow through each filter bag and prevent local air flow short circuits.
2. Maintenance and replacement
Replacement cycle: It is conventionally recommended to replace it every 3 to 6 months. The specific frequency depends on the change in resistance – when the resistance reaches twice the initial resistance (for example, the initial resistance is 60Pa and the final resistance is 120Pa), it must be replaced.
Replacement operation
Before replacement, turn off the air conditioning unit, wear a dust mask and gloves, and avoid contact with contaminants on the filter material (especially in biological laboratories, old filter materials should be treated as medical waste).
After replacement, check the frame seal. After starting the unit, test the particle concentration at the air outlet (to ensure there is no leakage).
Cleaning requirements: For non-disposable filter materials (such as washable polyester fibers), surface dust can be blown off with compressed air first, then rinsed with clean water (water temperature ≤40℃), dried and reused (up to 2 times to avoid filter material damage).
V. Limitations and Supplementary Plans
Medium-efficiency bag filters are only effective against particulate pollutants and cannot handle chemical odors, toxic gases or live microorganisms. Laboratories need to combine and supplement purification methods based on their shortcomings
The air purification effect in the laboratory depends on “correct installation + standardized maintenance”. For medium-efficiency bag filters, the following key points need to be focused on:
1. Installation specifications
System location: It must be installed in the air supply section of the air conditioning unit (after the primary filter and before the high-efficiency filter) to prevent unfiltered air from bypassing the filter (the frame seal needs to be checked, with the gap ≤0.1mm).
Airflow direction: Install strictly in accordance with the “airflow arrow” on the filter bag (the fluffy side of the filter material should face the airflow). Reverse installation will cause a sudden increase in resistance and a decrease in filtration efficiency.
Spacing reservation: A spacing of 5 to 10cm should be reserved between the filter bags to ensure uniform air flow through each filter bag and prevent local air flow short circuits.
2. Maintenance and replacement
Replacement cycle: It is conventionally recommended to replace it every 3 to 6 months. The specific frequency depends on the change in resistance – when the resistance reaches twice the initial resistance (for example, the initial resistance is 60Pa and the final resistance is 120Pa), it must be replaced.
Replacement operation
Before replacement, turn off the air conditioning unit, wear a dust mask and gloves, and avoid contact with contaminants on the filter material (especially in biological laboratories, old filter materials should be treated as medical waste).
After replacement, check the frame seal. After starting the unit, test the particle concentration at the air outlet (to ensure there is no leakage).
Cleaning requirements: For non-disposable filter materials (such as washable polyester fibers), surface dust can be blown off with compressed air first, then rinsed with clean water (water temperature ≤40℃), dried and reused (up to 2 times to avoid filter material damage).
V. Limitations and Supplementary Plans
Medium-efficiency bag filters are only effective against particulate pollutants and cannot handle chemical odors, toxic gases or live microorganisms. Laboratories need to combine and supplement purification methods based on their shortcomings
Chemical pollution: Combined use of activated carbon filters (for adsorbing volatile organic substances) or chemical filters (for acidic and alkaline gases, such as impregnated activated carbon, alumina filter materials);
Biological contamination: A high-efficiency filter (HEPA, intercepting microorganisms ≥0.3μm) is connected in series at the back end. If necessary, ultraviolet disinfection lamps are installed (to assist in killing air microorganisms).
In high-humidity environments (such as hot and humid laboratories) : Choose waterproof filter materials (such as coated polyester fibers) to prevent the filter materials from absorbing moisture and getting moldy.
Resumen
Medium-efficiency bag filters are the “key bridge” for laboratory air purification. Their selection should closely focus on three core aspects: filtration efficiency, filter material, and suitable scenarios. At the same time, their value should be maximized through standardized installation and maintenance. For laboratories with high cleanliness and high risk (such as biosafety and precision instrument rooms), it is necessary to build a composite purification system of “primary, medium, high and functional filters” to comprehensively ensure the safety of the experimental environment and the reliability of data.
Biological contamination: A high-efficiency filter (HEPA, intercepting microorganisms ≥0.3μm) is connected in series at the back end. If necessary, ultraviolet disinfection lamps are installed (to assist in killing air microorganisms).
In high-humidity environments (such as hot and humid laboratories) : Choose waterproof filter materials (such as coated polyester fibers) to prevent the filter materials from absorbing moisture and getting moldy.
Resumen
Medium-efficiency bag filters are the “key bridge” for laboratory air purification. Their selection should closely focus on three core aspects: filtration efficiency, filter material, and suitable scenarios. At the same time, their value should be maximized through standardized installation and maintenance. For laboratories with high cleanliness and high risk (such as biosafety and precision instrument rooms), it is necessary to build a composite purification system of “primary, medium, high and functional filters” to comprehensively ensure the safety of the experimental environment and the reliability of data.
