In a laboratory at the Charlotte Medical School in Berlin, researchers carefully open a petri dish. The lid is labeled “Operating Room Air Sample,” yet the contents remain pristine—a testament to the 99.97% filtration efficiency of the HEPA filters in the hospital’s ventilation system.
What is Filtration Efficiency?
Filtration efficiency, this seemingly simple percentage, is actually a core indicator for measuring filter performance. It precisely describes the filter’s ability to remove particles of a specific size from the air. Typically, it refers to the ratio of the number of particles captured by the filter to the total number of particles entering the filter.
This seemingly simple definition actually embodies the depth of sophisticated science. For example, a HEPA filter labeled “99.97% filtration efficiency for 0.3-micron particles” means that only 3 out of every 10,000 particles of 0.3 microns can pass through the filter.
What are the testing methods for filtration efficiency?
In the Trenntech production facility, engineers rigorously test ULPA filters according to the EN 1822 standard. This standard specifies the Most Penetrating Size (MPPS) test method, which is currently recognized globally as the most accurate filter testing method.
“The testing process is extremely precise,” explains the project engineer. “We generate monodisperse aerosols of a specific particle size and simultaneously measure them upstream and downstream of the filter using a specialized particle counter. This allows us to measure a 99.999% filtration efficiency for 0.1-micron particles.” It’s important to note that filtration efficiency is not constant. As filters are used over time, accumulated particles can cause a complex change in efficiency, initially increasing slightly before gradually decreasing.
Practical Applications of Filtration Efficiency
In hospital operating rooms, filtration efficiency translates from a theoretical parameter into a matter of life and death. For example, transplant operating rooms typically use U15-grade ULPA filters, achieving a filtration efficiency of 99.9995% for 0.12-micron particles. This figure directly relates to the patient’s infection risk. Every 0.001% increase in efficiency could potentially save a life.
Similarly, in semiconductor factories, filtration efficiency is directly linked to product quality. Chip manufacturing has extremely stringent requirements for environmental cleanliness; ULPA filters on the production line must maintain an efficiency of over 99.999%, otherwise, product yield will significantly decrease.
Filtration Efficiency Selection Guide
Experts recommend that users choose filter efficiency based on their actual needs:
- General Office Environment: ePM1 Filters with an efficiency of 60% or higher are sufficient to meet requirements;
- Hospital general areas: HEPA grade (≥99.97% for 0.3-micron particles);
- Operating rooms and laboratories: ULPA grade (≥99.999% for 0.12-micron particles); Semiconductor manufacturing: U17 grade or higher (≥99.99999% for 0.12-micron particles).
We need to recognize that choosing a filter is not simply about maximizing efficiency. The key is to match actual needs and find the optimal balance between efficiency, resistance, and cost.
Without precise measurement, there is no reliable quality. A deep understanding and precise control of filtration efficiency is the cornerstone of Trenntech’s competitive advantage in custom filter manufacturing. On the path to a cleaner environment, this seemingly simple percentage will continue to lead technological innovation and safeguard various fields from industrial manufacturing to healthcare.