Which situation allows transformers containing non-flammable liquids in Class II, Division 1 locations?

The situation that allows transformers containing non-flammable liquids in Class II, Division 1 locations is when they are in vaults that comply with specific regulations. In hazardous locations such as Class II, Division 1 areas, which are specifically designated for locations that may contain combustible dust, stringent regulations apply to ensure safety and minimize risks.

Transformers that use non-flammable liquids can still pose a risk of electrical failure, which could ignite combustible dust in the surrounding area. By placing these transformers in vaults that meet certain regulatory criteria, safety measures are heightened. These vaults are designed to contain any potential leaks, provide adequate ventilation, and limit the exposure of the transformer to hazardous conditions. Compliance with regulations ensures that these safety features are in place, thereby mitigating risks associated with electrical equipment in dust-laden environments.

The other choices present situations that do not adequately address the safety requirements needed in Class II, Division 1 locations. For example, installing transformers without specific requirements fails to consider the associated risks; simply placing them above ground level does not inherently ensure compliance with safety standards; and locating them in open areas may expose them to conditions that could result in igniting combustible dust, which is not compliant with safety practices.