Every product listing and purchase request on ChemAbout goes through automated screening before it is published. The same screening applies to guest submissions, account submissions, and supplier responses. Two checks run on every submission: the CAS number, and the text content.
CAS-number screening
A submitted CAS number is checked against two layers:
- A core blocked set that is always active: chemicals on Chemical Weapons Convention Schedule 1 (nerve and blister agents) and top-tier drug precursors. This layer is built into the platform and does not depend on any external service being available.
- Every regulatory list marked "procurement blocked" in the compliance directory — CWC Schedules 1–3, China's Precursor Chemical Categories 1–3, China's Explosive Precursor Chemicals list, US DEA List I/II chemicals, UN 1988 Convention Tables I/II, and the Australia Group Chemical Weapons Precursors list. When a list in the directory is updated, the blocked set updates with it.
CAS numbers are normalized before checking: dash variants, invisible characters, and full-width digits are converted to a canonical form, so formatting tricks do not bypass the check.
Text screening
Product names, descriptions, and request text are screened in English and CJK languages against blocked term categories, including:
- claims of prescription, medical, clinical, or pharmaceutical grade, or of fitness for human therapeutic use — ChemAbout does not host medicinal-product offers;
- narcotic and psychotropic drug terminology;
- weapons-grade or military-grade claims.
The exact term list is deliberately not published.
The three procurement policies
Each regulatory list in the compliance directory carries one of three procurement policies, and they behave differently:
- Blocked — chemicals on these lists cannot be published as products or purchase requests at all.
- Restricted — publication is not automatically blocked, but compound pages for these chemicals display a compliance advisory and carry no publish call-to-action.
- Open — reference lists (for example warning and disclosure lists) shown for information; they do not gate publishing.
What happens when content is blocked
A blocked submission is rejected with a generic error. The specific matched term or list is not disclosed in the rejection, and matches are logged server-side. This is deliberate: disclosing the match would make the screen easy to probe and work around.
What screening is — and is not
Screening exists to keep controlled chemicals and medicinal-product claims off the platform. It is not a regulatory compliance service: passing the screen does not mean a chemical, listing, or transaction is compliant in your jurisdiction. Supplier qualification, licensing, permits, and regulatory compliance remain the responsibility of the parties — see What ChemAbout is (and is not).