Agency of necessity is a legal concept that arises in specific situations where an agent acts on behalf of a principal without prior agreement, typically due to an emergency. To better understand this concept, let's break down the conditions under which agency of necessity can arise:

1. There is some emergency: The situation must be urgent and require immediate action. For example, if a property is at risk of damage or loss, the agent may need to act quickly to protect the owner's interests.
2. There are no pre-existing contracts: The agent should not have any prior contractual obligations that would normally govern the relationship between the agent and the principal. This means that the agent is stepping in to act without an established agreement.
3. The person charged with responsibility can get instructions: Ideally, the agent should have the ability to communicate with the property owner or obtain instructions. However, in emergencies, it may not always be possible to reach the owner, which is why the agency of necessity is invoked.

In summary, agency of necessity can only arise under these specific conditions, where there is an urgent need for action, no prior contractual obligations exist, and the agent has the ability to seek instructions from the property owner. If these conditions are met, the agent can act in the best interest of the principal to mitigate potential harm or loss.