Colorless or sometimes yellowish , styrene (C3H8) has a sweet odor, detectable from 0.15 ppm. It is a very harmful organic compound, harmful by inhalation and can cause skin and eye irritation (R36/38). Flammable between 0.9% and 6.8% volume, styrene vapors can form explosive mixtures. It also has reprotoxic effects , and the IARC* classifies it as a possible carcinogen for humans (Group 2B).
*IARC: International Agency for Research on Cancer (part of the WHO World Health Organization)