In the field of air filtration, we consistently pursue one goal: to capture as many harmful particulate matter as possible while minimizing airflow obstruction. This goal is perfectly embodied in the perpetual interplay between two core concepts—MPPS efficiency and operating pressure drop. Like two ends of a balance scale, they jointly define the performance boundaries of a filter.
1. What is MPPS (Most Penetrating Particle Size)?
MPPS is not a specific numerical value, but rather a scientific concept and testing method. It reveals a counterintuitive phenomenon: for most high-efficiency filters (such as HEPA/ULPA ), it is not necessarily true that larger particles are more easily captured, nor that smaller particles are more difficult to capture. Within the 0.1 to 0.3 micrometer range, there exists a particle size point where the combined effects of inertial impaction, interception, and diffusion mechanisms are weakest, making it the easiest particle to penetrate the filter. This particle size is the MPPS.
Key takeaway: MPPS (Maximum Per Particle Size) represents the weakest link in a filter. Therefore, a filter’s true efficiency should not be measured by its efficiency with a specific large particle (e.g., 5μm), but rather by its efficiency in capturing the most cunning and easily penetrating MPPS particles. This is the origin of HEPA filter efficiency (e.g., 99.97% @ 0.3μm)—0.3 microns is generally considered the MPPS point in early filter designs.
2. What is Operating Pressure Drop (Initial Pressure Drop and Final Pressure Drop)?
Resistance refers to the pressure loss generated when air flows through a filter. It directly determines how much “cost” the system needs to expend to drive the air.
- Initial Pressure Drop: The resistance of a brand-new, clean filter operating at its rated airflow.
- Operating Initial Pressure Drop/Final Pressure Drop: As the filter’s dust holding capacity increases, the resistance rises continuously. When the resistance rises to a certain specified value (final resistance), it means the filter is “overburdened” and needs replacement.
- Key takeaway: Resistance is directly related to operating costs. Higher resistance requires more powerful fans, leading to higher energy consumption, increased noise, and potentially shorter equipment lifespan. Throughout the filter’s lifespan, electricity costs far exceed its initial purchase cost.
3. Balancing MPPS and Operating Pressure Drop
The relationship between these two is not simply one of mutual reinforcement, but rather a trade-off between the two – a “technological game.”
| Comparison Dimensions | MPPS Efficiency | Operating Pressure Drop |
| Target Purpose | Ultimate Purification: Achieving the highest single-pass filtration efficiency to ensure environmental cleanliness | Economical and Energy-Saving: Achieving the lowest energy consumption and operating costs to achieve sustainable development. |
| Technological Impact | Typically requires finer fibers, denser structures, and deeper filter media folds to enhance capture efficiency. | Typically requires looser fiber gaps and a more open structure to reduce airflow obstruction. |
| User Concerns | Results-Oriented: Focusing on whether the final air quality meets standards (e.g., operating rooms, chip manufacturing plants). | Process-Oriented: Focusing on electricity bills, equipment noise, and maintenance frequency. |
| Contradictory Relationship | Increasing efficiency often leads to increased resistance. For example, increasing the density or thickness of fiberglass to capture more MPPS particles directly leads to narrower air passages and a surge in resistance. | Reducing resistance may sacrifice efficiency. While using coarser, sparser fiber materials allows for unobstructed airflow, those “cunning” MPPS particles can still get in. |
From the above materials, it’s clear that MPPS efficiency defines the safety baseline, while operating resistance sets the cost boundary. As a professional air filter manufacturer from Frankfurt, Trenntech believes that an excellent filtration solution must, while meeting minimum MPPS efficiency requirements, select products with the lowest possible initial resistance and highest dust holding capacity (i.e., slower resistance growth). We should move away from the misconception of “efficiency-only” or “price-only” approaches and find the optimal balance between clean air and green operations for our specific application scenarios.