Top 5 frequently asked questions about dynamic pass box?

  • 28, 05, 2021

What is the key difference between dynamic pass box and static pass box?, how to replace HEPA filter in dynamic pass box ... Here are 5 commonly asked questions about dynamic pass box. Let's find the answers with VCR! 

Question 1: What is the key difference between dynamic pass box and static pass box?

Answer: The key difference between dynamic pass box and static pass box is that dynamic pass box has self-cleaning system, while static pass box does not. 

Dynamic pass box is equipped with a suction HEPA filter of around 0.3 microns. A static pass box doesn't have a filter. The dynamic pass box also has a differential pressure gauge ranging from 0 to 250 pa. It is also equipped with a motor blower for blowing out dust particles.

The static pass box just has an air-lock system to prevent ambient air from entering or clean air from disappearing from the cleanroom

Question 2: What does differential pressure gauge on dynamic pass box measure?

Answer: The differential pressure gauge on dynamic pass box is used to measure the differential pressure of HEPA filter. We use the pressure gauge to monitor the HEPA filter life

Almost all of the differential pressure gauges on purification equipment are used to test the filter integrity, which reminds customers when it's needed to exchange the filters.

Question 3: When we need to change HEPA filter in dynamic pass box? 

Answer: Each filter has its particular final pressure drop. Final pressure drop point (sometimes called “Final Resistance.”) is the pressure drop at which a filter is meant to be replaced.

Filter manufacturers will provide final pressure drop of their filters so that customers can check and replace HEPA filter in dynamic pass box.

Normally, the final pressure drop is about 250~450 pa. That's the reason why the measuring range of differential pressure gauge commonly used on purification equipment for HEPA filter is 0~250 pa or 0~500pa. 

Question 4: Can VCR give me the instructions to replace HEPA filter in dynamic pass box?

Answer: When replacing HEPA filter, first we have to stop the pass box from running.

When replacing a new HEPA filter, special attention should be paid to protecting the integrity of the filter paper during unpacking, handling, installation, and use, and it is forbidden to touch the filter paper by hand to cause damage

Before installation, hold the new HEPA filter up to the ground to visually check if the HEPA filter is leaky due to transportation or other reasons.If there is a bug, the filter can not be used.

When replacing, remove scatter plate and used-HEPA filter. Wipe the efficiency tool holder with alcohol and install the new one. Note that the arrow marks on the filter correspond to the direction of the airflow.

Question 5: While the fan of dynamic pass box is running, can we open the door?

Answer: We cannot open the doors of pass box during running. Dynamic pass box is equipped with a 2-door interlocking system. Therefore, the doors are locked automatically during running, and we cannot open both doors at the same time.


Vietnam Cleanroom Equipment (VCR) specializes in providing cleanroom equipment for construction contractors. We provide high-quality products with competitive prices and large quantities nationwide. The equipment includes:

Differential pressure gauge, FFU Fan Filter Unit, Pass box, Clean room air filter, HEPA box, Clean booth, cleanroom steel door, Isolator cabinet, and other equipment

For details, please refer to Vietnam cleanroom equipment official website



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