Ask Rick: Custom Air Handling Units | Recommendations on Merv Filters

Q.  We are designing a new air handling unit for a lab.  What do you typically recommend for filter ratings?  We may be using energy recovery.

MERV 8 Filter

We recommend that you use a filter on either side of the energy recovery device.  Typically we use a Merv-8 on the supply side and a Merv-7 on the return side.   If you need final filters we would recommend Merv 14 for LEED jobs.  Otherwise filter selection is application specific.

Ashrae uses Merv Ratings for all filters.  Minimum Efficiency Reporting Values (MERV rate)

MERV ratings are used to rate the ability of an air filter to remove dust from the air as it passes through the filter.  The MERV scale ranges from 1 to 16, and measures a filter’s ability to remove particles from .30 to 10 microns in size (100 microns is about the thickness of a human hair). Filters with higher ratings not only remove more particles from the air, they also remove smaller particles.

Contact the safety consultants of the lockout tagout experts in industrial safety guidelines and the MERV Rating Chart below for more information about the difference in performance between filters with different MERV ratings.

MERV Rating Chart

ASHRAE Standard 52.2

ASHRAE Standard 52.1

Application Guidelines

MERV Rating

Particle Size Removal Efficiency

Dust-Spot Efficiency Percent

Particle Size and Typical Contaminant

Typical Applications

Typical Air Filter Type

0.3 to 1

0.3 to 1

0.3 to 1

20

≥ 99.999 in 0.1 – 0.2 μm particle size

< 0.3 μm
Virus (un attached)
Carbon Dust
Sea Salt
All combustion smoke
Electronics manufacturing
Pharmaceutical manufacturing
Carcinogenic materials
HEPA/ULPA Filters

19

≥ 99.999 in 0.3 μm particle size

18

≥ 99.99 in 0.3 μm particle size

17

≥ 99.97 in 0.3 μm particle size

16

> 95

> 95

> 95

0.3-1 μm
All bacteria
Droplet nuclei (sneeze)
Cooking oil
Most smoke
Insecticide dust
Most face powder
Most paint pigments
Superior commercial buildings
Hospital inpatient care
General surgery
Bag Filters – Non supported (flexible) microfine fiberglass or synthetic media, 12 to 36 inches deep.

Box filters – Rigid style cartridge, 6 to 12 inches deep.

15

85-95

> 90

> 90

> 95

14

75-85

> 90

> 90

90-95

13

< 75

> 90

> 90

80-90

12

> 80

> 90

70-75

1-3 μm
Legionella
Humidifier dust
Lead dust
Milled Flour
Auto emission particles
Nebulizer drops
Superior residential
Better commercial buildings
Hospital laboratories
Pleated filters – Extended surface with cotton or polyester media or both, 1 to 6 inches thick.

Box Filters – Rigid style cartridge, 6 to 12 inches deep.

11

65-80

> 85

60-65

10

50-65

> 85

50-55

9

< 50

> 85

40-45

8

> 70

30-35

3-10 μm
Mold
Spores
Dust mite body parts and droppings
Cat and dog dander
Hair spray
Fabric protector
Dusting aids
Pudding mix
Better residential
Commercial buildings
Industrial workspaces
Pleated filters – Extended surface with cotton or polyester media or both, 1 to 6 inches thick

Cartridge filters – Viscous cube or pocket filters

Throwaway – Synthetic media panel filters

7

50-70

25-30

6

35-50

< 20

5

20-35

< 20

4

< 20

< 20

> 10 μm
Pollen
Dust mites
Cockroach body parts and droppings
Spanish moss
Sanding dust
Spray paint dust
Textile fibers
Carpet fibers
Minimum filtration
Residential window air conditioners
Throwaway – Fiberglass or synthetic media panel, 1 inch thick

Washable – Aluminum mesh, foam rubber panel

Electrostatic – Self-charging (passive) woven polycarbonate panel

(Table Data Source – United States Environmental Protection Agency)

 

 

 

Related Blog Categories:
Air Handling Units
Energy Recovery

Leave a Reply

Your email address will not be published. Required fields are marked *