These three terms get thrown around interchangeably, and most of the time people mean roughly the same thing: breaking a job down into steps, identifying the hazards in each step, and defining the controls. But they aren't perfectly identical, and the differences matter when a client, a contract, or a prequalification reviewer asks for one by name.
Job Hazard Analysis (JHA) — the most general term, and OSHA's preferred one. You take a task, break it into its basic steps, identify the hazard in each step, and specify how it's controlled. It's the foundational document, applicable across almost any trade or task.
Job Safety Analysis (JSA) — in practice, essentially the same tool as a JHA. The naming is largely regional and organizational preference; many employers say JSA where others say JHA, and the structure is the same step/hazard/control breakdown. If a client asks for a JSA and you have a JHA, you're usually looking at the same document by a different name — but it's worth matching the term they use.
Activity Hazard Analysis (AHA) — this is the one that's genuinely distinct. The AHA is the format specified for federal and U.S. Army Corps of Engineers work under EM 385-1-1. It's more structured than a typical JHA — it ties in required inspections, training, and competent/qualified personnel for the activity, and it's expected in a specific form on those contracts. If you're doing government or Corps work, "AHA" is not just a synonym; it's a required deliverable in a required format.
Which one do you actually need?
It comes down to who's asking and what work you're doing. General industry or standard construction task planning — JHA (or JSA if that's your client's term). Federal or Corps of Engineers contracts under EM 385 — AHA, in its specific structure. The mistake to avoid is assuming they're always interchangeable and handing a client the wrong format for their requirement.