How often do I need to change my air filter?
There are many factors that can determine when an air filter should be changed. How often the HVAC unit runs, air quality, humidity and other factors can vary greatly from application to application. For most 1”, 2” and 4” deep panel or pleated style filters, it is usually recommended to change the filter every 2-3 months. In many commercial and industrial applications static pressure can be monitored and the filters can be changed when they reach their recommended final resistance in inches of water gauge.


What is MERV?
MERV means Minimum Efficiency Reporting Value which was developed by the American Society of Heating, Refrigeration and Air Conditioner Engineers – ASHRAE. MERV values vary from 1 to 16. The higher the MERV value is the value the more efficient the filter will be in trapping airborne particles.


Understanding MERV  (National Air Filtration Association – NAFA)

Filter MERV Descriptions.

MERV Std 52.2 Intended Dust

Spot Efficiency

Std 52.1 (2)



Particle Size





Filter Type

1-4 <20% 60 to 80% > 10.0 μm Residential/Minimum
Light Commercial/
Minimum Equipment Protection
Charging (passive)
Washable/Metal Foam/ Synthetics
Disposable Panels
Fiberglass / Synthetics
5-8 <20 to 60% 80 to 95% 3.0-10.0 μm Industrial Workplaces
Better / Residential
Paint Booth / Finishing
Pleated Filters
Extended Surface Filters
Media Panel Filters
9-12 40 to 85% >90 to 98% 1.0-3.0 μm Superior/Residential
Better/Industrial Workplaces
Better Commercial Buildings
Non-Supported/Pocket Filter
/Rigid Box
Rigid Cell / Cartridge
13-16 70-98% >95 to 99% 0.30-1.0 μm Smoke Removal
General Surgery
Hospitals & Health Care
Superior / Commercial Buildings
Rigid Cell / Cartridge
Rigid Box / Son-Supported /
Pocket Filter
MERV Std 52.2 Efficiency  Typical Applications  Typical Filter Type
17-20 (1) 99.97%-99.9999% Hospital Surgery Suites
Hazardous Biological
Nuclear Material

Note: This table is intended to be a general guide to filter use and does not address specific applications or individual filter performance in a given application. Refer to manufacturer test results for additional information.

(1) ASHRAE does not have a test procedure for HEPA testing and has thus dropped the MERV 17-20 classifications.

(2) ANSI/ASHRAE 52.1 ranges are provided for reference only. The ANSI/ASHRAE 52.1 Standard was discontinued as of January 2009.


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