Blue smoke
Blue smoke turns up in 2 fields: asphalt, electronics. Here is what it means to the people in each one.
Blue smoke in asphalt
Bluish haze rising off the mix that signals overheated binder and premature hardening.
A blue-tinged smoke from a truck or the mat that tells experienced hands the mix came out of the plant too hot. Overheated binder gives off light oils and oxidizes, which stiffens it before it ever reaches the road and shortens pavement life. White vapor is a different thing: it is usually steam from moisture left in the aggregate.
"Blue smoke boiling off that truck, shoot it, I bet the plant's running 340 and cooking the oil."
Blue smoke in electronics
The visible smoke released when an electronic component burns out.
The acrid smoke emitted when a semiconductor, capacitor, or resistor fails catastrophically due to overvoltage, reverse polarity, or excessive current. The joke among technicians is that electronic components run on magic blue smoke, and once it escapes, the part is dead.
"I hooked up the bench supply backward and let the blue smoke out of the microcontroller."