modern germicidal lamps resemble a compact flourescent lamp without the phosporus coating,and as such work on the same principal.

older versions of the germicidal lamp resembles an incandescent,in this lamp a tungsten filament heats some mercury vapor causing an arc to form at the tips of the lead wires,while shorting out the filament.

actually one more thing, a germicidal lamps are made out of quartz instead of glass like CFL has glass....

The reason is because quartz does not block UV

i knew that