Which of the following materials is least likely to be found in a Class I hazardous location?

In a Class I hazardous location, the focus is on environments where flammable gases, vapors, or liquids are present. These areas pose potential explosion risks due to the presence of these hazardous materials.

Potable water is least likely to be found in a Class I hazardous location because it does not fall into the category of flammable gases or vapors. In contrast, natural gas, acetylene gas, and propane gas are all flammable substances that can create explosive atmospheres, making them relevant in the context of hazardous locations.

Since potable water is non-flammable and is commonly used for drinking and hygienic purposes, it inherently does not pose the same risks associated with flammable materials that necessitate special safety considerations in hazardous environments. Therefore, it is entirely appropriate to identify potable water as the least likely material to be found in a Class I hazardous location.