The Rule That Governs Every Page
This site owns no test equipment and has taken no measurements. Every performance number on it comes from somewhere else, and the sentence containing it names where. That is the whole rule, and it is worth stating plainly because the opposite is common: a great deal of writing in this category implies hands-on testing through phrasing alone, without ever claiming it outright, and a reader has no way to tell the difference.
What a Sourced Figure Looks Like
Agency guidance, standards documentation, peer-reviewed findings, or a manufacturer specification. The first three are reported as findings. The fourth is reported as a claim the manufacturer makes, never as a verified result, because that is what it is.
What You Will Not Find
No removal percentage, coverage area, decibel figure or extraction rate presented as something anyone here determined. No ranked list of models presented as a head to head trial. If this site ever acquires instruments and begins measuring, that work will appear labelled as ours, dated, with the instrument named, and this page will say exactly what we own.
Standards We Treat as Load-Bearing
Certifications do most of the work that brand names pretend to do. Three matter constantly here.
- NSF/ANSI 42 covers aesthetic effects: chlorine taste and odour, particulates. It is not a health claim.
- NSF/ANSI 53 covers health effects: lead, cysts, VOCs and similar. This is the certification that matters for contaminants that can hurt you.
- AHAM Verifide CADR is the only air purifier performance number generated under a common test protocol, which is why we size purifiers by CADR rather than by the square-footage figure on the box.
A product certified to a standard is certified for specific named contaminants, not for everything. We name the contaminant, not just the standard.
How We Choose What to Recommend
We recommend a specification, not a model number. Stock, pricing and even the internals of a given model change without notice on this equipment, and an article that names one unit is out of date within a season. So each page tells you the specification that solves your problem, then links to the current options that meet it. That also means we never have a reason to steer you toward whichever unit paid the most.
Where We Tell You Not to Buy Anything
A large share of indoor air and moisture problems are structural. Bulk water entering a basement, a crawl space open to bare soil, a bath fan vented into an attic, or mold across more than roughly ten square feet are not consumer-equipment problems, and putting a machine in the room treats the symptom while the cause continues. Those pages say plainly that the next step is a contractor.
How We Size Equipment
Sizing is where most consumer purchases in this category go wrong, so we do it by the underlying physics rather than the number printed on the box. Air purifiers are sized by room volume and a target number of air changes per hour, which produces a required CADR, not by the square-footage figure manufacturers print, which assumes a ceiling height and an air change rate they rarely state. Dehumidifiers are sized by floor area and how wet the space actually is, then adjusted for temperature, because a compressor loses capacity as the room gets colder and a basement in winter is a different machine's job.
Where that arithmetic is useful we build it into a calculator on the page rather than asking you to do it, and we state the assumptions the calculator makes. A sizing tool that hides its assumptions is just another box claim.
What We Do With Conflicting Evidence
Several questions in this field genuinely do not have a settled answer, and the page says so rather than picking the version that supports a purchase. Where the published evidence is mixed, the page says it is mixed, describes what the stronger studies found, and separates the part that is established from the part that is marketed. Health claims get the most conservative reading available, because the cost of overstating one is borne by the reader and not by us.
Where it matters, a page also names the evidence that would change its recommendation. A recommendation that cannot be falsified is an opinion dressed as a finding, and naming what would move it gives you something to check it against.
What We Will Add When We Have Instruments
This site does not currently own test equipment, and until it does there are no measurements of ours anywhere on it. Nothing here is framed as though there were. When that changes, first-hand measurements will appear labelled as ours, dated, with the instrument named and the conditions described, and this section will say exactly what we own and how it is calibrated. Anything unlabelled will remain a cited figure.
We are stating this plainly because the opposite is common. A great deal of writing in this category implies hands-on testing through phrasing alone, without ever claiming it outright, and readers have no way to tell the difference. The distinction is easy to make and we would rather make it.
Corrections
When we get something wrong we change the page and note what changed. If you can show a figure here is incorrect, tell us and include the source.