No, I dont use an O2 monitor like some other suggest.
Its a step processas noted earlier my kilns are digitally controlled. So for example: I may heat the parts to 10,000 degrees for 5 hours, at the 5 hour point my kiln will drop the temp to quench temp say 6000 degrees, well we know that the charcoal is an excellent insulator, so I allow the crucible with parts to normalize to the new lower temp, figure about an hour, once its normalized I will turn on the air at a specific volume approximately 20 minutes prior to quench.
The cool piece is that my controllers have a settable alarm, so I can be machining a barrel or whatever, and it will beep, reminding me to turn on the air.
The air provides two purposes, the first, it aids in the formation of colors, but more importantly it circulates the water thus avoiding inconsistent cooling. Hot steel parts dumped in water will cause the water immediately touching the part to turn into steam, this could form steam pockets which will not cool the parts as well as the water. The air provides the circulation, maintaining a constant flow of cool water against the partsall this in fractions of a second.
