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Replacement carbon pre-filter pack

GermGuardian Filter O Carbon Replacement Filters (4-Pack) FLT51CB4 replacement filter

Filter O Carbon Replacement Filters (4-Pack) (part FLT51CB4) fits GermGuardian AC3200, GermGuardian AC3250, GermGuardian AC5109W and GermGuardian AP3250, according to the official GermGuardian product page.

Official GermGuardian fit · checked

GermGuardian models that use Filter O Carbon Replacement Filters (4-Pack) FLT51CB4

This filter is listed for 4 models. Open a model to see its complete list of primary, optional, and specialty filters.

Official package contents

What's in the box

From the linked official GermGuardian product page. Marketplace packs can differ, so compare before you buy.

Filter O Carbon Replacement Filters (4-Pack) FLT51CB4

Before you order

What to check in a FLT51CB4 listing

  • The listing names part FLT51CB4. Similar-looking filters are not proof of fit.
  • Your purifier is one of the compatible models: GermGuardian AC3200, GermGuardian AC3250, GermGuardian AC5109W and GermGuardian AP3250.
  • The pack size and pieces included match what you need. Genuine and third-party filters can differ.
  • The total price with shipping, seller feedback, and delivery estimate work for you.

Care guidance

Replacement schedule

GermGuardian recommends replacing the activated carbon filter layer every 2 to 3 months depending on use. Package contains 4 carbon replacement filters.

Usage conditions can affect service life. Follow the cited manufacturer guidance for this part.

Free calendar reminder

Never forget a filter change

Enter the date you installed the filter and we'll make a repeating calendar reminder based on the official replacement schedule.

Filter O Carbon Replacement Filters (4-Pack) filter set FLT51CB4

The calendar reminder starts 3 months after this date and repeats on that schedule.

Your date is processed only in this browser. The .ics calendar file is generated locally on your device and is not uploaded to this site.

Compare compatible options

These share at least one compatible model but may do a different job, such as a carbon pre-filter or a specialty version. Check each part page before buying.

Replacement filter set

Filter O

FLT5100

Frequently asked questions

How often should I replace the GermGuardian Filter O Carbon Replacement Filters (4-Pack) (FLT51CB4)?

GermGuardian recommends replacing the activated carbon filter layer every 2 to 3 months depending on use. Package contains 4 carbon replacement filters.

Which GermGuardian models use the Filter O Carbon Replacement Filters (4-Pack) FLT51CB4?

According to the official GermGuardian product page, Filter O Carbon Replacement Filters (4-Pack) (FLT51CB4) fits GermGuardian AC3200, GermGuardian AC3250, GermGuardian AC5109W and GermGuardian AP3250. Verify the model label on your unit before ordering.

Do aftermarket FLT51CB4 filters work?

Marketplace listings may be from the manufacturer or a third party. Match the exact part number FLT51CB4, review the listing details, and verify the model label on your unit before buying.

Official compatibility record

Manufacturer source

Official Guardian Technologies product page identifies Filter O carbon replacement filter 4-pack, SKU FLT51CB4, as compatible with models AC3200, AC3250, AC5109W and AP3250.

Guardian Technologies GermGuardian FLT51CB4 - Filter O Carbon 4-Pack

Source compatibility checked 2026-08-29. Recheck the listing and your purifier label before ordering.