Industry Insights & Technical Resources

When purchasing bag filters, common parameters are "592×592×600 mm, 6 bags, rated air volume 3400 m³/h". But the same outer frame may also be equipped with 8 bags, 10 bags or 12 bags. The more bags and the longer the bag length, the greater the rated air volume? In fact, the three are not a simple linear relationship. The number of bags and bag length mainly affect the effective filtration area, filter material wind speed, pressure drop and dust holding capacity. The selection should be based on the filtration level and actual operating conditions.

After the HVAC system replaces the filter, the air volume decreases. It is usually not as simple as "the new filter is of better quality and naturally has greater resistance." Common causes include mismatched filter selection, installation errors, actual air volume exceeding the rated value, and abnormalities in fan control or other components of the system. If you increase the fan frequency without measuring the resistance first, it may increase energy consumption and noise, or even damage the filter element.

Laboratory ventilation design cannot select fans only based on the number of air changes. The air supply volume, exhaust volume and room pressure difference must be calculated in conjunction, taking into account the room volume, experimental equipment exhaust, personnel load, door gap leakage and safety level. Otherwise, it is easy to cause odor spillage, difficulty in opening the door, or energy waste.

In pharmaceuticals, food processing, biological laboratories, hospitals, marine environments and high-humidity industrial plants, ordinary HEPA filters may suffer from moisture in the filter material, increased pressure drop, corrosion of the frame, or aging of the sealant. When selecting a humidity-resistant HEPA, you should not just look at “100% humidity resistance”, but also distinguish between three working conditions: high relative humidity, short-term condensation, and direct water droplet contact.

The low price of air filters does not necessarily mean low overall cost. For air-conditioning boxes, clean rooms, pharmaceuticals, electronics factories and industrial ventilation systems, the dust holding capacity of the filter will directly affect the replacement cycle, manual maintenance, system energy consumption and the life of the post-stage HEPA filter. Therefore, when purchasing, you should not only compare the unit price and filtration level, but also compare the dust holding capacity and resistance changes under the same test conditions.

If the HEPA filter pressure drop is too high, it will lead to a decrease in system air volume, insufficient air exchanges in the clean room, and increased fan energy consumption. In severe cases, it will also affect the room pressure difference and the stability of the production environment. Engineers should not replace the filter directly based on the pressure difference value alone, but should first confirm whether the measurement is accurate, and then determine whether the filter element is clogged, the air volume is abnormal, or the system resistance is a problem.

HEPA filter selection cannot only look at the appearance size or filtration efficiency. If the size is too small and the air volume is too large, the initial resistance will increase, the noise will increase, and the life of the filter element will be shortened; if the size is too large, the cost of the box, air duct, and installation space will increase. The core of project selection is to calculate the headwind speed based on the design air volume, and then check the rated air volume, initial resistance and system residual pressure.

When purchasing VAV variable air volume valves, CAV constant air volume valves, Venturi valves or electric air volume regulating valves, the control signal will directly affect actuator selection, control accuracy, fault diagnosis and building automation system access. 0–10V and 2–10V belong to analog control, while Modbus belongs to digital communication. The three cannot be directly interchanged just by changing the wiring method.