In ALOHA, a Level of Concern (LOC) is a threshold value of a hazard (toxicity, flammability, thermal radiation, or overpressure); the LOC is usually the value above which a threat to people or property may exist.

Whenever you use ALOHA to analyze a chemical release scenario, you must choose one or more LOCs. ALOHA will provide you with common default values, or you may choose up to three of your own LOCs. For each LOC you choose, ALOHA estimates a threat zone where the hazard is predicted to exceed that LOC at some time after a release begins. These zones are displayed on a single threat zone picture.

ALOHA includes the following LOCs to model different hazards: