[12.1.2.5] Radiant power evaluated according to its capacity to produce erythema of the untanned human skin; i.e., in accordance with the erythemal effectiveness of the flux. Unit: W. (See erythemal action spectrum.)

Note: An obsolete term (retained for reference purposes only) of erythemal flux is the erythemal unit (EU) or E-viton (erytheme), which is equal to the amount of radiant flux that will produce the same erythemal effect as 10 microwatts of radiant flux at wavelength 296.7 nm.