To extinguish an electronic device battery fire, which two substances should be used?

Using a halon extinguisher in combination with an H2O extinguisher is considered a suitable method for extinguishing an electronic device battery fire. Halon is a clean agent that works by interrupting the chemical reaction of the fire, making it effective for electrical fires as it doesn't leave residue or cause further damage to electronic equipment. The H2O extinguisher can also be used in certain circumstances, although care must be taken with electronic devices. When properly applied, water can help cool the battery and prevent re-ignition, especially if the fire involves lithium-ion batteries that may release flammable gases.

This option is recognized for providing a dual approach—halon for the initial suppression and water for cooling, which can be particularly useful in managing battery fires where thermal runaway might occur. Choosing this combination reflects an understanding of fire dynamics and proper safety protocols when dealing with electronic devices.