Overview
UVCB stands for substances of Unknown or Variable composition, Complex reaction products, or Biological materials. These cannot be pinned down by a single formula or CAS number. Their makeup shifts with the source or the process, so a fixed chemical description does not hold.
Key point
A UVCB does not behave like a clean, well defined substance. Petroleum fractions and some chlorinated paraffins are common examples.
Because the composition is variable, a UVCB is described by its source and process rather than by a precise structure. That is why a single CAS number often cannot capture exactly what is inside.
Note: general educational information, not legal advice. Check the official source before relying on it.