M
Mercury (Hg)
Definition
Mercury (Hg) is one of the ten restricted hazardous substances under RoHS Directive 2011/65/EU, restricted at a maximum concentration value of 0.1% (1000 ppm) by weight per homogeneous material. Mercury was historically used in fluorescent lamps (compact fluorescent lamps — CFLs), mercury-containing switches and relays, and measuring instruments. Several Annex III exemptions exist for mercury in specific lamp types and measuring instruments where substitution is technically difficult. The transition to LED lighting has significantly reduced mercury use in consumer lighting EEE, though certain professional lighting and measuring instrument exemptions remain active.
Source
Directive 2011/65/EU, Annex II; Annex III exemptions for mercury in specific lamp types and measuring instruments.
Practical Explanation (Compliance Context)
The most common mercury-related RoHS compliance issue concerns lighting EEE containing fluorescent lamps. Manufacturers of EEE containing backlights (e.g., older LCD displays with CCFL backlights) or fluorescent lamps must check applicable Annex III exemption validity. Mercury-containing switches, relays, and measuring instruments may also require Annex III or IV exemptions. Manufacturers transitioning from mercury-containing to LED or LED-backlit products should update their technical documentation to confirm mercury-free designs.