ADR-0004: Chemical identification is OCR on the CAS number

Status: Superseded by ADR-0030 — read order preserved, ranking replaced Date: 2026-09-02

Decisions

D-05 The camera reads the CAS number off the printed label, falling back to the chemical name

QR code scanning is kept as a secondary path for organisations that label their own containers. Barcode lookup is out of scope.

Context

R-10 records a contradiction in the source: the technology panel names a QR Code Scanner, while the screen-3 mockup frames a viewfinder on a supplier's acetone bottle bearing a printed label and a barcode. R-11 shows the chemical record keyed by CAS No. 67-64-1.

CAS numbers are short digit strings, globally unique, and present on virtually every compliant label — the most OCR-robust identifier available, and script-independent in a Thai/English mixed environment (R-18).

Rejected options

• QR only, as the technology panel says — rejected because it requires someone to have pre-labelled every container. A plant with hundreds of drums will not, and the emergency case is precisely the unfamiliar container nobody prepared.
• OCR on the chemical name — rejected as ambiguous across synonyms, trade names and two scripts. Kept only as the fallback when no CAS number is visible.
• Barcode lookup — rejected because no public barcode-to-chemical mapping exists and catalogue numbers are vendor-specific.
• Manual search only, cutting the camera — rejected: it removes the source's most distinctive feature along with the technical risk.

This ruling may not be re-decided

If a change contradicts this ADR: stop and raise it. Do not implement over it. In particular, do not promote name-OCR to the primary route because CAS reading is fiddly.

Consequences

Manual search must remain a first-class path, not a fallback — OCR will fail on damaged, handwritten and decanted-container labels, which are common.

Coverage

Upstream	Landed in	Evidence	Note
R-09	D-05	the Scan Chemical tile is this route's entry point
R-10	D-05	the QR-vs-barcode contradiction resolved in Context
R-11	D-05	CAS 67-64-1 adopted as the identifier