What purity does AHRI 700 require — what does “99.5% purity” mean?

The headline limits

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, which is spontaneously flammable in air. That is 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).

Related: AHRI 700 explained · Fake-refrigerant dangers · Compliance & quality