Is a higher MERV rating always better?

Not necessarily. Higher MERV filters capture more particles but create more airflow resistance. Using too high a MERV rating without system modifications can reduce efficiency and damage equipment.

What MERV rating do I need for allergies?

MERV 11-13 effectively captures allergens like pollen, mold spores, dust mites, and pet dander. This range offers excellent filtration without excessive airflow restriction.

MERV Ratings Explained: Choosing the Right Air Filter for Any Application

What is MERV?

MERV stands for Minimum Efficiency Reporting Value. It's an industry-standard rating system developed by ASHRAE that measures a filter's ability to capture particles of different sizes.

MERV ratings range from 1-20, with higher numbers indicating better filtration of smaller particles.

MERV Rating Comparison

MERV	Particle Size	Captures	Typical Use
1-4	>10 μm	Pollen, dust mites, carpet fibers	Minimal filtration
5-8	3-10 μm	Mold spores, dust, pet dander	Residential (standard)
9-12	1-3 μm	Legionella, humidifier dust, lead dust	Better residential
13-16	0.3-1 μm	Bacteria, tobacco smoke, sneeze droplets	Hospital, superior residential
17-20	<0.3 μm	Viruses, carbon dust, sea salt	Cleanrooms, surgery

Choosing the Right Filter

For Standard Residential

MERV 8: Good balance of filtration and airflow. Suitable for most homes without specific air quality concerns.

For Allergies or Pets

MERV 11: Captures smaller allergens while maintaining good airflow. Recommended for allergy sufferers.

For Respiratory Concerns

MERV 13: Captures bacteria and smoke particles. Best filtration for standard HVAC without modifications.

System Considerations

Pressure Drop Impact

Higher MERV = more resistance. Check that your system can handle the filter:

Measure static pressure with current filter
Compare to equipment specifications
Upgrade to media cabinet if needed for high MERV

Filter Depth Matters

1" filters: MERV 8 max recommended
2" filters: MERV 11 possible
4-5" media filters: MERV 13+ without problems

Quality Filters In Stock

NOLT carries filters in all MERV ratings and sizes. Pro pricing and same-day delivery available.

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NOLT HVAC Team

Industry Experts & Technical Writers

Our team of HVAC professionals, certified technicians, and industry experts share practical knowledge to help contractors and technicians excel in their work. With decades of combined experience, we're committed to providing actionable insights.