The pulse energy of electrostatic discharge(ESD) will lead to the local heating, which also damage the electron tube.
PS: The lowest 100V electrostatic voltage is going to damage the components; However, the electrostatic voltage what human being feels is generally between 2–4KV. Apparently, it is reallly easy for us to damage the electronics components with electrostatic discharges(ESD).
Electrostatic discharge - Wikipedia
