I don't know what breakdown voltage means.
Is that how high the voltage has to be before the electricity will 'jump' through the air? That's what it sounds like from context, but I want to be sure.
( Bob Todd whee, Mon 30 Jul 2007, 15:10, archived)

Pretty much
For electricity to jump across a metre of air requires a potential difference of about 1,000,000 volts.
( Lord Gnome, Mon 30 Jul 2007, 15:13, archived)