When purchasing HEPA/ULPA filters, “99.97% filtration efficiency for 0.3-micron particles” has become a widely accepted standard. However, a crucial fact often overlooked is that MPPS (Most Penetrating Particle Size) is not a constant 0.3 microns. It is influenced by the filter media material, structure, and the physical properties of the particles, and can vary from 0.1 microns to 0.3 microns in different applications. The commercial value of this lies in avoiding the unnecessary costs of “over-filtration” or the more dangerous quality risks caused by “under-filtration.”
I. Why Does MPPS Change?
The essence of MPPS is the lowest point of efficiency resulting from the combined effects of Brownian diffusion (dominated by small particle size) and inertial interception (dominated by large particle size). When the diameter and packing density of the filter media fibers change, the balance point of these two effects shifts, causing MPPS to change.
- Traditional fiberglass filter media: MPPS typically close to 0.3 microns.
- New thin filter media/membrane filter media: MPPS may be as small as 0.1-0.15 microns.
This means that a filter designed for 0.3-micron particles may have efficiency weaknesses at even smaller particle sizes.
II. What size particles do you need to intercept?
1. Lithium battery industry: Focus on ultrafine particles and heavy metal dust.
- Real challenges: Electrode material dust (such as nano-sized carbon black, lithium cobalt oxide), and aerosols generated during the slurry mixing process, with particle sizes mainly distributed in the 0.1-0.2 micron range. These particles can cause battery self-discharge and micro-short circuits.
- Procurement strategy: Select filters with validated MPPS in the 0.1-0.2 micron range, and pay attention to their specific filtration efficiency data for heavy metal particles. Ensure the filter can effectively protect critical areas such as drying rooms and slurry mixing workshops.
2. Pharmaceutical Industry: Intercepting Microbial Aerosols and Powders
- Real Challenge: Bacterial monomers are typically 0.5-5 micrometers in size, but the aerosol carriers (droplet nuclei ) they rely on for propagation have a diameter of 0.1-0.3 micrometers. Many active pharmaceutical ingredients (APIs ) also have submicron-sized powder particles.
- Procurement Strategy: Aseptic core areas must use filters with MPPS (Multi-Particle Power) efficiency. Attention should be paid to the actual efficiency of filters for particles around 0.2 micrometers, and their efficiency stability under simulated real-world conditions (such as disinfectant environments) should be verified.
3. Semiconductor Industry: Defending Against Molecular-Scale Contaminants and Process Chemicals
- Real Challenge: Airborne molecular-scale contaminants (AMCs), as well as gaseous molecules of acids, alkalis, and dopants, have particle sizes far smaller than 0.1 micrometers. Furthermore, metal particulate matter generated during manufacturing processes is mostly between 0.05-0.2 micrometers, and these are major culprits for chip defects.
- Procurement Strategy: Recognize the limitations of traditional HEPA/ULPA filters. While these filters can filter particles, they need to be used in combination with chemical filters to address AMC (Area-Mixed Contamination). When purchasing, suppliers should be requested to provide efficiency curves for filters with particle sizes of 0.1 microns and below, and these should be considered in conjunction with chemical filtration solutions.
III. Procurement Action Guidelines: From “Procurement by Grade” to “Procurement by MPPS”
- 1. Ask the Right Questions: Don’t just focus on “What is the efficiency for 0.3 microns?”, but ask, “What is the measured MPPS of this filter? Can you provide an efficiency curve for the entire particle size range?”
- 2. Analyze Your Own Process: Collaborate with the production department to analyze the particle size distribution of the main contaminants and identify the particle size range that needs to be prioritized for protection.
- 3. Precise Matching: Match the specific particle size you need to protect against with the filter’s MPPS point and efficiency curve, selecting the product with the highest efficiency in the critical particle size range, rather than simply the highest grade product.
Therefore, Frankfurt-based professional HEPA/ULPA supplier Trenntech strongly recommends that customers understand the variability of MPPS, move beyond the “0.3 micron” mindset, and fully demonstrate the filter’s actual application environment. Trenntech will provide the most cost-effective and technically targeted procurement solutions, achieving a win-win situation.