Wastes are considered reactive if they are __________ under normal conditions.

Wastes are considered reactive if they are unstable under normal conditions. This means that these materials are chemically unstable and can undergo violent reactions, such as explosions or the release of toxic gases, when subjected to heat, pressure, or when they come into contact with water or other substances. Recognizing the instability of these wastes is crucial for implementing proper handling, storage, and disposal measures to prevent hazardous incidents.

The other choices do not accurately describe the characteristics of reactive wastes. Non-hazardous materials do not pose a significant risk and therefore would not fall into the reactive category. Completely inert substances are substances that do not react chemically under normal conditions, thereby indicating they are safe and stable, which is the opposite of what defines a reactive waste. Non-reactive materials also indicate stability and safety, which means they do not pose the risks associated with reactive wastes. Understanding these distinctions is essential for ensuring safety in hazardous waste operations.