Resources
| 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) |
Average
Arrestance |
Particle Size
Ranges |
Typical
Applications |
Typical
Filter Type |
| 1-4 | <20% | 60 to 80% | > 10.0 μm | Residential/Minimum Light Commercial/ Minimum Equipment Protection |
Permanent/Self 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 Commercial 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 V-Cells |
| 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 V-Cells |
| MERV Std 52.2 | Efficiency | Typical Applications | Typical Filter Type | ||
| 17-20 (1) | 99.97%-99.9999% | Hospital Surgery Suites Cleanrooms Hazardous Biological Contaminants Nuclear Material |
HEPA ULPA |
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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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