MERV Rating (Minimum Efficiency Reporting Value)
MERV (Minimum Efficiency Reporting Value) is a rating system from 1-20 that measures air filter efficiency. Higher MERV ratings capture smaller particles, but also restrict airflow more. For DIY air purifiers, MERV 13-16 provides the best balance of filtration and airflow.
MERV ratings indicate what particle sizes a filter can capture: MERV 1-4 catches large particles like dust and pollen. MERV 5-8 captures mold spores and pet dander. MERV 9-12 traps fine dust and vehicle emissions. MERV 13-16 removes bacteria, smoke, and virus-carrying particles - this is the sweet spot for home air purifiers. MERV 17-20 is HEPA-grade, used in medical settings but often too restrictive for DIY applications.
MERV scale ranges from 1 (lowest) to 20 (highest filtration)
MERV 13-16 recommended for DIY air purifiers - captures virus particles
MERV 13 removes 90% of particles 1.0-3.0 microns (includes most bacteria)
MERV 16 captures 95%+ of particles down to 0.3 microns (surgical mask level)
Higher MERV requires more fan power - box fans work best with MERV 13-16