What purity does AHRI 700 require — what does “99.5% purity” mean?
The headline limits
| Parameter | Limit (single-component fluorocarbon) | What it protects against |
|---|---|---|
| Other volatile impurities | ≤0.5% by weight (≈99.5% purity) | Off-spec PT behaviour, capacity loss |
| Water | ≤10 ppm by weight | Ice at expansion devices; acid formation with POE oil |
| Non-condensables (air) | ≤1.5% by volume (vapour phase) | High head pressure, wasted power |
| Acidity | Limited (ppm-level) | Winding and copper attack |
| High-boiling residue | Limited (fraction of a %) | Fouled surfaces, blocked capillaries |
| R-40 (methyl chloride) | ≤300 ppm | The signature counterfeit adulterant — see below |
Flag: the exact per-fluid Table 1A cells sit behind AHRI's paywall; the figures above are corroborated through the standard's incorporation into 40 CFR Part 82 and consistent industry citation. We flag that rather than assert page-level access we don't have.
What 99.5% does and doesn't mean
The 0.5% allowance is for other volatile refrigerant-like substances — trace fluorocarbons from manufacture — not a licence for half a percent of anything. Water, air, acid and residue each carry separate, far tighter caps in different units (ppm, volume-%), which is why a single "purity %" on a certificate is less informative than the parameter list. A batch is conforming only when every row passes.
Why 10 ppm of water is worth the fuss
Ten parts per million reads absurdly strict until you follow the chemistry: modern systems run hygroscopic POE oil, and water plus ester at compressor temperatures yields organic acids — the front end of the acid–sludge–burnout cascade. Ice at the metering device is the acute symptom; acid is the chronic one. The limit is set where field damage statistics say it must be (mechanism in the oil guide).
The R-40 line: purity as safety
Most rows protect equipment; the 300 ppm methyl-chloride cap protects people. R-40 is the documented counterfeit diluent that reacts with aluminium to form trimethyl aluminium — spontaneously flammable in air — the mechanism behind fatal reefer-container explosions (full account in why fake refrigerant is dangerous). A conforming batch cannot carry meaningful R-40; an adulterated one fails on sight in a GC trace. It is the clearest single reason "tested to AHRI 700" and "genuine branded product" are two halves of the same assurance (authenticity checks).
From table to trust: how a certificate of analysis maps to these rows
The limits become practical the day a certificate of analysis (COA) lands on your desk, because a genuine COA is simply this table with measured values beside it. Reading one takes a minute once you know the correspondences: a purity/assay line by gas chromatography answering the 0.5%-impurities row (expect ≥99.5% for single-component fluids); a moisture line by Karl Fischer titration against the 10 ppm water cap; a non-condensables line, vapour-phase, against 1.5% by volume; acidity and high-boiling residue lines against their fractional limits; and — on batches where it matters — chloride or R-40 screening against the 300 ppm methyl-chloride cap that carries the safety weight (why). The verification habits that separate diligence from theatre: match the batch number on the COA to the cylinder stencil, not just the brand; check the laboratory identity and date (a named lab and a plausible test date, versus an undated template); and treat a supplier's inability to connect cylinder → batch → analysis as the finding itself. Honesty about roles belongs here too: as distributors we supply factory-sealed product from brands that publish conformity and provide batch documentation where the manufacturer issues it — we do not run the chromatograph, and the value we add is precisely the unbroken chain from that laboratory to your loading dock (the full paper set).
- AHRI Standard 700-2019, §§5.4–5.11 — contaminant limits — ahrinet.org.
- 40 CFR Part 82, Subpart F — incorporation by reference (corroborating the numeric limits) — epa.gov.
This guide is general information compiled from the cited sources — not legal, safety or engineering advice. Read our full disclaimer.
Related: AHRI 700 explained · Fake-refrigerant dangers · Compliance & quality