For many companies, upgrading existing cleanrooms is a more cost-effective option than building new ones. However, when procuring next-generation HEPA /ULPA filters to improve cleanliness or replace older products, many project teams focus on efficiency levels and price, neglecting crucial physical and system compatibility. These hidden pitfalls can lead to newly procured filters being unsuitable for installation or failing to meet performance standards, resulting in significant project delays and cost losses.
The following are the three most easily overlooked compatibility issues when procuring new HEPA filters in cleanroom retrofitting projects.
Issue 1: Installation Dimensions
This is the most common and fatal mistake. Procuring parties often assume that the new filter can be seamlessly replaced with the old model.
Core Risk:The mounting frame of the old cleanroom may have deformed due to age and stress, or the original construction standards may differ slightly from today’s standard dimensions. This minute difference of “millimeters” is enough to prevent the new filter from being installed or to create hidden problems.
Purchasing Guideline: Never order based solely on the model number or catalog size of an old filter. Before purchasing, a professional must measure the actual net space dimensions (width, height, depth) of each mounting slot at multiple points and record any potential frame deformation. This measured data should be included as a key technical attachment to the purchase order.
Issue 2: Sealing Method
Older cleanrooms may use outdated sealing technologies that are outdated and out of step with the design philosophy of new filters.
Core Risk: Traditional strip seals (relying on compressed sponge rubber) and modern knife-edge seals (relying on a metal knife edge cutting into a gasket) are two completely different technological approaches. Their mounting frame structures, required clamping forces, and sealing mechanisms are drastically different. Attempting to install a knife-edge seal filter on an old frame designed for strip seals, or vice versa, is destined to result in seal failure and leakage.
Purchasing Guideline: Clearly identify the sealing type of the old system. If a change in sealing method is required (e.g., upgrading from a strip seal to a more reliable knife-edge seal), the corresponding modification of the mounting frame must be included in the project budget and plan. Simply purchasing filters without considering frame compatibility is not feasible.
Issue 3: System Damping
New generation HEPA filters may differ in resistance characteristics from older products, directly impacting the balance of the entire airflow system.
Core Risk: The air supply system (fans, valves) of older cleanrooms was designed and tuned based on the initial and final resistance of the existing filters. If the newly purchased filters have significantly different initial resistance or resistance-to-dust-hold curves compared to the older models, it may lead to:
- 1. Insufficient Air current: Higher resistance in the new filters may reduce room airflow and air changes, resulting in substandard cleanliness.
- 2. System Overload: Increasing fan speed to maintain airflow may overload the motor and increase energy consumption and noise.
- 3. Airflow Imbalance: Using different batches or models of filters at different HEPA outlets can cause uneven resistance, disrupting the original room pressure gradient and airflow organization.
Purchasing Guidelines: Before purchasing, always request a detailed resistance curve diagram of the new filter from the supplier and compare it with the old data. Consult with HVAC engineers to assess whether the existing air system has sufficient capacity to accommodate this change. As engineers at Trenntech, a leading filtration solutions provider based in Frankfurt, often remind customers: “Filters are part of the air system, not a standalone product.”
Retrofitting an old cleanroom is a systems engineering project. When purchasing new HEPA filters, decision-makers must have a systems mindset that goes beyond “product specifications.” Before placing a purchase order, three key steps—on-site verification of installation dimensions, clear definition of sealing interfaces, and accurate assessment of system damping compatibility—are crucial to ensuring a successful retrofit project and avoiding costly rework.