How we evaluate compatible filters.

When we write that a filter is rated for a particular contaminant, that a part number cross-references a specific OEM model, or that a warranty position is protected by federal law, the claim is anchored to one of the following sources. Higher items in this list outrank lower items when they disagree.

1. AStandards-body documents. NSF International (info.nsf.org), AHAM, EN 1822 published text, ASHRAE 52.2, AAMI ST91, FDA Code of Federal Regulations. We cite these by standard number so you can verify directly at the issuer.
2. BManufacturer specification sheets. Downloaded from the manufacturer's own site, dated when retrieved. We do not rely on third-party reseller pages for spec claims because resellers have an incentive to round numbers favorably.
3. CGovernment and regulatory text. US Code (15 U.S.C. 2301-2312 Magnuson-Moss, 42 U.S.C. 300f Safe Drinking Water Act), FTC enforcement guidance, CMS Local Coverage Determinations.
4. DIndependent laboratory reports. Where a NSF-accredited lab or peer-reviewed paper has tested a specific filter or technology, we cite the report. These are rare for the consumer compatible-filter market.
5. ETrade associations. Water Quality Association, Asthma and Allergy Foundation of America, American Academy of Sleep Medicine guidance. Useful for consumer-facing thresholds (when does hard water become a problem, what GPG is "hard") but secondary to standards-body documents.

Our consolidated index of every standard cited across this site is at /standards. If a claim on our site is not linkable to one of the categories above, it is opinion, and we mark it as such.

The compatible-filter market is densely populated with phrases that sound like certifications but carry no verification. We do not treat the following as evidence that a product meets a standard:

• "NSF compliant." NSF compliance is a marketing claim by the manufacturer. It is not the same as NSF certification, which requires testing by an NSF-accredited laboratory and issues a verifiable certification number. Without a number, the phrase means the manufacturer believes the product would pass — not that it has.
• "Tested to NSF standards." Tested by whom? At what lab? Reported where? "Tested to" without a third-party report is functionally identical to "not tested."
• "HEPA-style" or "HEPA-type." True HEPA is defined by EN 1822 classes H13 and H14 and captures 99.97% or better at 0.3 microns. "HEPA-type" is an unregulated marketing term typically meaning 90-99% capture at 1-2 microns, a substantially weaker performance.
• "Removes 99% of contaminants." Which contaminants? At what challenge concentration? Under what flow rate? Without a tested contaminant list and challenge protocol, the number is unverifiable.
• Amazon product reviews. Reviews on a product's own listing are gameable, frequently paid for, and not a substitute for independent verification. We cross-reference review patterns only as a tiebreaker, never as primary evidence.
• Influencer endorsements. Affiliate or sponsored relationships between content creators and manufacturers are rarely disclosed in compatibility content. We do not weight a recommendation based on social-media presence.

Generative AI is now capable of writing fluently incorrect content at scale. The public web is filling up with templated AI buying guides that look authoritative and cite nothing. We have a position on this.

That is the policy. Here is what the site actually ran on until October 2026: product pages were generated from a template, and the generated text asserted fit, performance and certifications that nobody had checked. We removed that text on 2026-10-16 and 2026-10-17, including the structured data that carried the same claims to search engines, and the generators that produced it are disabled in the repository. Section 04 describes what is left.

We do not test parts. There is no laboratory here, no sample programme and no measuring equipment. Product pages are built from a parts table we maintain — ASIN, brand, device model, part number, category — and from what the seller's own listing states. The headline, the specification table, the installation steps and the internal links are generated from those fields. Guides are written by hand against the documents in Section 01. We receive no price or stock data at all, which is why no price appears anywhere on this site.

If something here is wrong, write to contact@danorie.com with the page address and what is wrong with it. We correct the page and record the correction below.

The standards landscape changes. NSF revises certification protocols. New emerging contaminants get added to NSF/ANSI 401. The FDA reclassifies devices. CMS updates Medicare LCDs. What actually triggers a change here:

Each guide's editorial footer shows its publish date and its most recent edit. We do not run a fixed review cycle and we are not going to claim one: a cadence nobody keeps is worse than no cadence. If a guide looks stale on a topic where the standards have moved, tell us and we will read it.

• ×Rankings and "best" picks. We do not test parts, so we do not rank them. The category lists on this site are lists; the rule that sets their order is printed above each one.
• ×Paid product placement. No brand is paying for its position on this site. The directory is sorted by category coverage, not by margin.
• ×Generated product prose at scale. This site did it: 856 product pages carried template-written experience, fit and performance claims that nobody had checked. The text came off on 2026-10-16 and 2026-10-17 and the generators are disabled. The pages are still here as a parts catalogue — the part number, what the listing states, and the Amazon link.
• ×Sponsored reviews disguised as editorial. When manufacturers or distributors send sample products, we will disclose it explicitly inside the guide and add a permanent "Sample provided" note in the editorial footer.
• ×Affiliate links disguised as neutral references. Every Amazon link on this site is an affiliate link. The disclosure appears on every page that contains them. We use the standard rel="nofollow sponsored" attribute on every commercial outbound link.

Pick any factual claim on this site and trace it. The reference is either inline in the article, in the article's References & Standards section, or in the consolidated /standards page. If a claim is not traceable, that is an editorial error and we want to fix it. Email us at the address below.

This site is run by one person. The repository is private, so there is no commit history for you to audit — we are not going to claim otherwise. What stands in its place is Section 04, which states exactly what we check and what we do not, and the correction record kept there. No listing on this site is paid placement, and no manufacturer has any arrangement with us.