Effected from 2006, control use 6 hazardous substances percentage in a product: Pb, Hg, Cd, Cr6+, PBB and PBDE. The practice may have variance across countries, such as EU RoHS, China RoHS, Korea RoHS.
The chemical concentration can be tested in laboratory, or nowadays many factories equipped with a RoHS scanner for preliminary checking.
RoHS 2 is introduced in 2011 to cover all electrical/electronic equipment, cables and spare parts that enforced from Jul 22, 2019, RoHS compliance is a requirement for CE marking that product must comply with RoHS 2 before the CE mark can be applied on the product.
Also effective from Jul 22, 2019, RoHS 3 is enforced with 4 additional substances and limits as below: