What effect does blowing air over glowing embers have during a fire investigation?

Blowing air over glowing embers during a fire investigation increases the glow and can raise the temperature significantly, potentially enough to melt certain metals. When air is introduced, it enhances the combustion process by supplying oxygen, which can intensify the heat produced by the embers. This is particularly relevant in a fire investigation context, as investigators often need to determine the extent of the fire's impact on materials at the scene.

The other options, while related to fire behavior, do not accurately describe the primary effect of blowing air over embers. For instance, it does not extinguish the fire; rather, it can cause the fire to grow due to the added oxygen. It also does not typically generate explosive flames in this context unless there are volatile materials present. Although blowing air could theoretically aid in locating hidden fire spots by revealing the heat of smoldering materials, the most direct effect is the increase in temperature that can lead to melting metals.