can i use to remove moth ball smell by putting over return and supply for central ac/heat?

Hello there: YES, our activated cut-to-fit carbon filter shall be able to remove mothball odor. P.S. Please do replace the carbon filter every 3 months. Feel free to contact us if you have any further inquiry. Thank you!

How do I know this is actually activated carbon material and not just some plastic mesh sheet?

You know by reading reviews written by people, like me, who have purchased the pads. They are activated charcoal.

Can i use this for the germ guardian 4220 air purifier? (to cover the hepa filter)

While I am not familiar with the germ guardian 4220 air purifier, you can trim this pre-filter with scissors to fit any device, so I would think that the answer would be yes.

ASIN	B079PR4VF6
Best Sellers Rank	#292,952 in Home & Kitchen ( See Top 100 in Home & Kitchen ) #181 in Air Purifier Parts & Accessories
Brand	GreenR3
Brand Name	GreenR3
Compatible Air Purifier Models	Honeywell 17000
Compatible Devices	Furnace
Customer Reviews	4.5 out of 5 stars 1,206 Reviews
Item Dimensions L x W x Thickness	121.9L x 40.6W x 2.5Th Centimeters
Item Weight	0.23 Pounds
Manufacturer	GreenR3
Material	Carbon
Material Type	Carbon
Model Number	CUT-TO-FIT-CARBON-PRE-FILTERS-16-48-INCH
Number of Items	1
Product Dimensions	121.9L x 40.6W x 2.5Th Centimeters
Product Grade	New
Unit Count	1 Count

1-Pack Cut-to-Fit Carbon Pad 16 x 48 inches for Air Filters Charcoal Sheet fits Air Purifiers Range Hoods Furnace Filters removes Odor VOC Parts Accessories Replenishment and More

Details

Description

Specifications

Reviews

Common Questions