Essential Accessories for High Temperature Air Filters
High-temperature air filters are critical components in demanding environments such as industrial ovens, paint booths, sterilization systems, and pharmaceutical clean rooms. These filters are designed to operate reliably under extreme heat, often up to 300°C or higher.
However, while the filter media itself is vital, the accessories—including frames, gaskets, seals, and holding mechanisms—are just as important for maintaining performance and ensuring system safety. The wrong material or poor assembly can lead to air leakage, frame deformation, or even filter failure..
This article explores the key accessories used in high-temperature air filters and how each contributes to stable, long-lasting performance.
What material is used in high temperature air filters?
The choice of materials determines how well a filter performs under heat stress. In high-temperature systems, typical filter media and structural materials include:
Glass Fiber Media
Glass fiber (typically borosilicate micro glass fiber) is the primary material for manufacturing HEPA and medium/coarse efficiency high-temperature filter media. It exhibits excellent high-temperature resistance, typically sustaining temperatures from 250°C to 350°C. Pure glass fiber has a higher softening point, but the temperature resistance of the filter media is limited by the bonding agents and sealants used.
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Coarse-fiber Glass Media
This medium consists of relatively coarse, loosely structured fibers. Such materials are typically fabricated into flat or shallow pleated primary filters rated at G4 or MERV 8, specifically designed for use as primary pre-filters in high-temperature filtration systems.
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Micro Fiber Media
These fibers, made from borosilicate, have diameters in the submicron range and are processed into uniform filter paper through a precise wet-forming process. To maximize filtration efficiency and airflow, this medium is engineered into mini-pleat or deep-pleat structures for manufacturing HEPA and ULPA filters. High-efficiency capture of minute contaminants—including particles at the most penetrable size of 0.3 microns—is critical for ensuring clean process air quality at elevated temperatures in industries such as pharmaceuticals and electronics baking.
Synthetic Fiber Media
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Polyester Material
Polyester fiber offers significant cost-effectiveness with excellent abrasion resistance and mechanical strength. Polyester filter media is primarily used for medium-to-low temperature pre-filtration at G4 efficiency. Its continuous operating temperature is typically limited to approximately 120°C to 150°C. Although it decomposes at elevated temperatures, its high dust-holding capacity and superior moisture resistance (exceeding that of glass fiber) make it the preferred economical medium for HVAC systems and many industrial primary filtration applications.
Freudenberg and Japanese companies supply most high-temperature polyester materials on the market. Chinese manufacturers are breaking through barriers to develop new high-temperature polyester materials—let's look forward to their progress.
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Aramid Material
Aramid fibers exhibit outstanding flame retardancy and high strength. Their continuous operating temperature typically ranges from approximately 200°C to 220°C. In mid-to-high-end filtration applications requiring both heat resistance and flame retardancy, they serve as a key alternative between glass fibers and ultra-high-performance synthetic fibers.
Metal Mesh
Metal Mesh Media offers distinct professional advantages over fiber filter media in high-temperature filtration applications. It sacrifices some primary filtration efficiency in exchange for exceptional temperature resistance, mechanical strength, and reusability.
Metal Mesh Media is primarily made of high-performance alloys such as stainless steel (SS304/SS316), nickel alloys, or other heat-resistant alloys. The maximum continuous operating temperature of metal filter media far exceeds that of all fibrous media. Stainless steel alloys can withstand temperatures up to 600°C, while certain specialty alloys can even endure instantaneous temperatures of approximately 1000°C. Its washability and reusability make it commonly used in the food industry as oil filters or G1 primary filters.
What are the Common Holding Frame Materials?
In high-temperature applications, filter frame materials are typically limited to metals, with stainless steel being the most reliable and commonly used option:
- Stainless steel offers excellent high-temperature resistance and corrosion resistance. It can easily withstand continuous operating temperatures up to 250°C or even higher without experiencing creep or severe oxidation. Common applications include drying ovens, paint spray lines, and cleanroom exhaust filtration in the pharmaceutical and food industries.
- Galvanized Steel: Offers robust construction and cost-effectiveness. Suitable only for moderate temperatures. Its heat resistance limit is relatively low, typically around 200°C. Above this temperature, the galvanized coating may burn off or oxidize, leaving the frame unprotected and prone to rust. Consequently, it is generally used in medium-to-high temperature applications, not extreme heat.
- Aluminum Alloy: Not suitable for truly high temperatures. Aluminum alloy has a significantly lower melting point than steel and experiences rapid mechanical strength degradation at elevated temperatures, typically usable only below 100°C. Consequently, it is not considered a suitable filter frame material for high-temperature environments.
SS304 vs. SS316 Filter Frames — Which Performs Better Under Heat?
The frame holds the filter together and keeps it stable under thermal expansion. The two most common materials are SS304 and SS316 stainless steel.
- SS304 Stainless Steel:
Highly durable and cost-effective, suitable for most high-temperature applications up to 870°C in dry environments.
- SS316 Stainless Steel:
Contains molybdenum, which increases resistance to corrosion and chemical attack—ideal for humid or steam-heavy conditions.
RT Air Filtech Recommendation:
For general oven or furnace use, SS304 is usually sufficient.
For pharmaceutical, sterilization, or chemical applications, SS316 provides superior corrosion protection and longevity.
What Gaskets and Seals are Needed for High Temp Filters?
When selecting gaskets and sealing materials for high-temperature filters, the key lies in ensuring the materials can withstand sustained high operating temperatures, thermal expansion/contraction cycles, and maintain chemical stability to prevent air bypass in the filtration system. Common high-temperature gasket and sealant materials are primarily concentrated in the fields of silicone, polytetrafluoroethylene (PTFE), and inorganic fibers. The temperature resistance of these materials far exceeds that of ordinary polyurethane (PU) or EPDM rubber.
