We read filter spec sheets so you do not have to.

Every brand selling cheap compatibles has the same incentive: maximize margin by cutting whatever the buyer cannot easily verify. Carbon weight you cannot weigh. HEPA grade you cannot test. NSF certifications you cannot audit. The result is a marketplace where two filters at very different prices look identical in product photos but perform very differently in service.

That is the problem we care about, and we are honest about how far we get with it: we do not test parts, so we cannot tell you which of two listings performs better. What we can do is quote what each listing states, and cite the manufacturer's own document where we have found it. We do not make recommendations.

When you click an "Amazon" link from this site and buy a filter, we receive a small commission from Amazon. This costs you nothing extra. It is the only way we make money. We do not accept paid placement, sponsored reviews, or vendor relationships, and no manufacturer pays for the brand positions in our directory.

The commission is small enough that we have no reason to recommend a worse filter just because it pays better. The 50-cent difference between Filter A and Filter B does not move the needle. The trust difference between recommending the right filter and the wrong one ends this business.

The Magnuson-Moss Warranty Act (15 U.S.C. 2301-2312) prohibits manufacturers from voiding your warranty solely because you used a third-party replacement part. The FTC acts on it: on 3 July 2024 its staff sent warning letters to eight companies over warranty terms tied to authorized parts or service, four of them air purifier brands -- the FTC's notice. Most retailers do not mention it. We cite it because it is what gives compatible filters a legitimate place in the market.

When a manufacturer claims their warranty is voided by a compatible filter, they are usually wrong about the law. They would need to prove that your specific compatible caused the specific malfunction. A failed compressor cannot be denied because of an aftermarket water filter on a different system.

Read the full Magnuson-Moss explainer

We will:

• 01Cite OEM specifications from manufacturer documentation, not marketing pages
• 02Reference NSF/ANSI, AHAM, EN 1822, or other independent certification bodies by their actual standard numbers
• 03Explicitly state when we have no testing evidence beyond the published specs
• 04Update guides when the underlying products or certifications change

We will not:

• 01Recommend filters with vague "NSF compliant" or "HEPA-style" claims
• 02Accept paid product placement, sponsored guides, or vendor-funded testing
• 03Generate filter pages with templated AI content at scale to chase rankings