Per Koch Bulletin K985-A, the Koch Permanent Galvanized Steel Washable Filter is a completely washable, reusable air filter designed for air or grease applications. Per Koch K985-A, Type MS all-steel filters are designed for a wide range of uses and can be operated at 300-600 FPM. The media consists of crimped wire and expanded metal cloth, which Koch K985-A states "provides superior dust catching ability and a life cycle up to four times longer than conventional filters." This media is enclosed in a durable metal frame.
What you get: washable metal-frame filters, sold by the case
Each variant is a complete metal-frame washable filter sized for standard HVAC and grease-application openings. Available in 1″ and 2″ depths, sold by the case in the carton quantities shown:
-
1″ depth filters:
-
16″x20″x1″ — 12 filters per case
-
16″x25″x1″ — 12 filters per case
-
20″x20″x1″ — 12 filters per case
-
20″x25″x1″ — 12 filters per case
-
24″x24″x1″ — additional size — 12 filters per case
-
2″ depth filters:
-
16″x20″x2″ — 6 filters per case
-
16″x25″x2″ — 6 filters per case
-
20″x20″x2″ — 6 filters per case
-
20″x25″x2″ — 6 filters per case
-
24″x24″x2″ — additional size — 6 filters per case
Custom and additional sizes (such as 24″x24″ in 1″ and 2″ depths) are available beyond the K985-A published table. Per Koch K985-A, "Please consult the factory for other sizes and configurations."
About the handles you see in product photos
The pictured filter shows bail handles, but filters ship without handles by default. Per Koch K985-A: "Filters are furnished without handles, but both bail and ring types are available upon request." If your application needs handles — for frequent removal in commercial kitchen exhaust hoods, equipment access panels, or any setting where the filter is pulled and washed often — contact RTF support before ordering and we'll arrange handles (bail or ring) on your case. Just let us know which handle type and how many filters need them.
Permanent Galvanized Steel Filter construction (per Koch K985-A)
-
Material: Galvanized Steel
-
Koch product type: Type MS (Bulletin K985-A)
-
Media: Crimped wire and expanded metal cloth (per Koch K985-A)
-
Frame: Durable galvanized steel frame
-
Operating range: 300-600 FPM (per Koch K985-A)
-
Service life: Per Koch K985-A, "life cycle up to four times longer than conventional filters"
-
Reusable: Completely washable (per Koch K985-A)
-
Available depths: 1″ and 2″ (in this RTF lineup); 4″ depth available on request per Koch K985-A
-
Handles: Filters ship without handles by default. Bail or ring handles available on request — see "About the handles you see in product photos" above, or contact RTF support before ordering.
-
Doubled airflow option: Per Koch K985-A, "Both steel and aluminum filters can be operated at twice the CFM capacities listed above, with corresponding increases in pressure drop." (Steel and aluminum specifically; consult Koch for stainless.)
-
1/8″ and 3/8″ depths: Available on request — request a quote for these custom-thin variants.
Published performance data (per Koch K985-A, Type MS)
The following table reproduces Koch K985-A's published performance data for the Galvanized Steel Permanent Filter line at the sizes carried in this RTF lineup:
| Nominal Size |
Actual Size |
Rated CFM |
Initial Resistance |
Average Arrestance |
| 16″x20″x1″ |
15.50 x 19.50 x 0.875″ |
640 |
0.050″ w.g. |
71% |
| 16″x25″x1″ |
15.50 x 24.50 x 0.875″ |
800 |
0.050″ w.g. |
71% |
| 20″x20″x1″ |
19.50 x 19.50 x 0.875″ |
800 |
0.050″ w.g. |
71% |
| 20″x25″x1″ |
19.50 x 24.50 x 0.875″ |
1000 |
0.050″ w.g. |
71% |
| 16″x20″x2″ |
15.50 x 19.50 x 1.75″ |
640 |
0.100″ w.g. |
76% |
| 16″x25″x2″ |
15.50 x 24.50 x 1.75″ |
800 |
0.100″ w.g. |
76% |
| 20″x20″x2″ |
19.50 x 19.50 x 1.75″ |
800 |
0.100″ w.g. |
76% |
| 20″x25″x2″ |
19.50 x 24.50 x 1.75″ |
1000 |
0.100″ w.g. |
76% |
Average Arrestance is reported per ASHRAE 52.1 (older standard); these permanent metal filters are positioned as equipment protection and grease capture rather than fine particulate filtration.
Cleaning and maintenance (per Koch K985-A)
Per Koch K985-A, the Permanent Metal Washable Filter is designed for in-service cleaning rather than disposal-and-replace. Koch's published maintenance procedure:
-
Wash: Per Koch K985-A, "Simply wash away dirt with hose or soapy water."
-
Re-coat with adhesive: Per Koch K985-A, "Recoat with adhesive spray before re-using."
This permanent design is what gives metal filters their cost advantage over disposable filters — one filter, washed and recoated as needed, replaces many disposable filter changes over its service life.
Air or grease applications (per Koch K985-A)
Per Koch K985-A, Permanent Metal Washable Filters are specified for both air and grease applications. This dual-application capability reflects two main use cases:
-
HVAC air filtration: Equipment protection and primary particulate capture in commercial and residential HVAC systems where reusable filtration is preferred over disposable filters — especially in dusty environments where rapid loading would shorten disposable filter life.
-
Commercial kitchen exhaust: Range hoods, grill hoods, and other foodservice exhaust applications where grease-laden vapor must be filtered before exhaust ductwork. The metal frame and washable construction handle the high-temperature, grease-saturated airstream that would destroy fiber-based filters. Required in many jurisdictions for foodservice fire-safety compliance.
About permanent metal washable filters
Permanent metal filters trade off particulate efficiency (the average arrestance values are in the 71–76% range per Koch K985-A) for two critical advantages over disposable filters: reusability (washable cycles instead of replacement) and grease/temperature tolerance (metal mesh stands up to grease and heat that would saturate or melt fiber media). For applications where fine particulate filtration is the goal — office HVAC, sensitive equipment, indoor air quality — you'll want a higher-efficiency disposable pleated filter (MERV 8+) instead. For equipment protection, primary capture, kitchen exhaust, and any setting where filter changes need to be infrequent, permanent metal filters are the right specification.
Sizing and ordering notes
-
Match nominal size to your filter slot. Per Koch K985-A, actual size for 1″ nominal-depth filters is 0.875″ (7/8″) deep, and actual size for 2″ nominal-depth filters is 1.75″ (1-3/4″) deep.
-
Each variant ships in the case quantity shown. Order multiple cases by adjusting the quantity at checkout.
-
Custom thin filters: 1/8″ and 3/8″ depths are available on request from Koch.
-
Need handles? Filters ship without handles by default. Bail or ring handles available on request — contact RTF support before placing your order so we can arrange handles on your case.
-
For grease/kitchen applications: Replace or wash on your maintenance schedule per local fire code requirements (typically 30 days for active foodservice).
-
Cleaning: Per Koch K985-A, hose or soapy water; recoat with adhesive spray before re-using.
Koch product literature
Detailed product specifications and complete performance data for Koch Permanent Metal Washable Filters (Type MS galvanized steel and Type MA aluminum) are published in Koch Bulletin K985-A: Permanent Metal Washable Filters Product Specification PDF (Koch Filter Corporation).
