CSLB C-20 HVAC ContractorVentilation and Air DistributionEasy
A technician is explaining filtration to a homeowner. What does a higher MERV rating primarily indicate about an air filter?
- AIt reduces the need for duct sealing
- BIt allows a higher airflow rate through the duct system
- CIt captures smaller airborne particles and provides better filtration
- DIt increases the static pressure rating of the blower motor
Show answer & explanationAnswer & explanation
Correct answer: C. It captures smaller airborne particles and provides better filtration
MERV (Minimum Efficiency Reporting Value) rates a filter's ability to capture particles of specific sizes; higher MERV numbers trap smaller particles more effectively, improving indoor air quality but typically increasing pressure drop.
Why the other options are wrong
- A. Filtration and duct sealing are unrelated code requirements.
- B. Higher MERV filters are denser and typically restrict airflow more, not less.
- D. MERV rates the filter, not the blower motor's static pressure capability.
MERV Rating
A standardized scale (1–16 typically for residential) rating a filter's efficiency at capturing particles of various sizes.
- Higher MERV = smaller particles captured
- Higher MERV usually = higher pressure drop
- Residential systems commonly use MERV 8–13
Memory trick: More MERV, More capture, More resistance.