Bag-Type Dust Filter: Basic Performance Data and Applications

2025-07-15 16:07:36

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“ Bag filters combine a large media area with high dust-holding capacity and low resistance. Review grades, airflow, service life, and uses in HVAC and industry. ”

Bag-type dust filters are common components in air filtration equipment for capturing solid particles such as dust, fibers, and pollen. Their bag construction increases the filter-media area, improving dust-holding capacity and service life. They are widely used in industrial and commercial facilities as well as some residential applications. Their basic performance data and practical application ranges are detailed below.

Basic Performance Data

The key performance parameters of a bag-type dust filter are filtration efficiency, dust-holding capacity, pressure drop, and suitability for different air velocities. Data vary considerably by filter grade. Common classifications and typical values are as follows.

Performance parameter | Coarse bag filter (G1–G4) | Medium-efficiency bag filter (F5–F9)

Filtration efficiency | 40%–90% for particles ≥5 μm; G4 can exceed 90% | 50%–95% for particles ≥1 μm; F9 approaches the lower efficiency limit of HEPA filtration

Dust-holding capacity | 100–300 g/m², depending on media thickness and material | 200–600 g/m²; synthetic-fiber media generally outperform cotton media

Initial pressure drop | 50–100 Pa at rated airflow | 80–150 Pa at rated airflow

Final pressure drop | 150–300 Pa; replacement is required at this level | 250–400 Pa; replacement is required at this level

Rated airflow | 500–3,000 m³/h per bag | 300–2,000 m³/h per bag

Filter media | Nonwoven fabric, nylon mesh, metal mesh, and similar materials | Ultrafine glass fiber, composite synthetic fiber, polyester fiber, and similar materials

Temperature resistance | Normally ≤80°C; some metal-mesh products can withstand 120°C | Normally ≤100°C; glass-fiber media can withstand 150°C

Core Characteristics

Structural Advantages

• A multi-bag design provides an unfolded media area three to five times larger than that of a panel filter. At the same airflow, it lowers air velocity and pressure drop while increasing dust-holding capacity. With equivalent media, a bag filter can hold two to three times as much dust as a panel filter.

Grade Characteristics

• Under the EN 779 classification, bag filters generally span coarse grades G1–G4 and medium-efficiency grades F5–F9. Medium-efficiency bag filters such as F7–F9 can capture fine particles in the 0.5–1 μm range, including smoke and fine dust fragments. They are often used as protective prefilters upstream of HEPA filters to extend HEPA service life.

Practical Applications

1. Industrial Facilities

• Factory ventilation: In machining, food-processing, and electronics-assembly workshops, bag filters remove airborne metal dust, food debris, and welding-fume particles. Coarse and medium-efficiency filters are often used in combination.

• Coating operations: In spray-booth prefiltration, F8–F9 medium-efficiency bag filters capture paint-mist particles and protect downstream high-efficiency filtration systems from contamination.

• Equipment air intakes: G3–G4 coarse bag filters remove sand, dust, insects, and other large atmospheric particles from the intake air of gas turbines, air compressors, and similar equipment.

2. Commercial and Public Buildings

• Central HVAC systems: F5–F7 medium-efficiency bag filters serve as the main return-air filtration stage in office buildings, shopping malls, and hotels. When used with a fresh-air system, they reduce indoor PM10 and PM2.5 concentrations.

• Hospital ventilation: F6–F7 medium-efficiency bag filters capture droplets and dust in ventilation systems serving general wards and corridors, providing basic filtration for clean areas.

3. Civil and Commercial Facilities

• Large air-handling units (AHUs): In centralized ventilation equipment for large supermarkets and stadiums, coarse bag filters pretreat incoming air and reduce dust accumulation in ductwork.

• Cleanroom support filtration: F7–F8 medium-efficiency bag filters serve as prefilters around clean zones in pharmaceutical workshops and laboratories, protecting the high-efficiency filters in core areas.

4. Special Applications

• Metro and tunnel ventilation: G4 coarse bag filters at fresh-air intakes in metro stations and underground tunnels capture windblown sand, fallen leaves, and other large debris from outdoors.

• Waste-treatment facilities: In waste transfer stations and incineration plants, coarse bag filters capture dust and solid fragments during exhaust-gas pretreatment, reducing the load on downstream purification equipment.

Operating Considerations

• Replacement interval: Depending on ambient dust concentration, coarse bag filters are generally replaced every 1–3 months and medium-efficiency bag filters every 3–6 months. A filter must be replaced when its pressure drop reaches the specified final value; otherwise, airflow will fall and energy consumption will rise.

• Installation: The bags must be able to expand fully. Wrinkles or compression can create excessive local air velocity and reduce filtration efficiency.

In summary, bag-type dust filters provide high dust-holding capacity, low resistance, and a broad range of grades. They play an important role wherever efficient particle capture and longer system service life are required, serving as a crucial intermediate stage within an air filtration system.

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