How to Write a JSA (With Example)

A Job Safety Analysis is five decisions written down: which job, what are its steps, what can hurt someone in each step, what are we doing about it, and is what's left acceptable. Everything else — the template, the logo, the signature block — is packaging. This page walks the five decisions with a real example from a trenching job, and ends with the mistakes that get JSAs handed back.

Step 1 — Pick the job narrowly

"Site work" is not a job. "Excavate a 7-foot trench for a sewer lateral at the north elevation" is. The narrower the scope, the more specific the hazards, and specificity is the whole value of the document. A JSA broad enough to cover three trades at once will name hazards so general that nobody reads them twice.

A good test: can you walk the job in your head from first move to cleanup? If yes, the scope is about right. If you need "and then depending on the day…", split it into two JSAs.

Step 2 — Break it into steps, in the order they happen

Walk the task and write what the crew physically does, in sequence. Most jobs land between four and ten steps. Fewer than four usually means the steps are too coarse to attach a hazard to; more than ten usually means you're describing a day, not a task.

Write steps as actions — "set the trench shield", "enter the trench to lay pipe" — not as outcomes. Each step should be something you could photograph someone doing. Setup, the work itself, and the pack-up all count: a surprising share of incidents happen during setup and cleanup, when the formal work hasn't started or has officially finished.

Step 3 — Name the hazard in each step

For every step, ask what could hurt someone — not what usually happens, what could. Name the energy or the mechanism: "cave-in of the trench wall", "contact with an energized buried line", "struck by spoil falling from the edge". Avoid abstract nouns like "unsafe conditions"; you cannot control a noun that vague.

One step can carry several hazards. That's normal — list them separately, because each one needs its own controls and its own risk score.

Step 4 — Write controls in hierarchy order

This is where good JSAs separate from paperwork. The hierarchy of controls, strongest first:

• Elimination — don't do the hazardous thing. Lay pipe from outside the trench; prefabricate at grade instead of at height.
• Substitution — do a less hazardous thing instead. A different product, a different method.
• Engineering controls — change the physical world so the hazard can't reach people: trench shields, guardrails, machine guarding, ventilation.
• Administrative controls — change what people do: permits, exclusion zones, competent-person inspections, sequencing, training.
• PPE — last, and only for what's left. PPE protects one person, only when correctly worn, and does nothing about the hazard itself.

A JSA whose control column reads "wear PPE, be careful" for a cave-in hazard is not a safety document — it's an admission that nobody thought about the job. If your controls are all at the bottom of the hierarchy, go back to step 4 and ask what would have to change for an engineering control to be possible.

Step 5 — Score the risk before and after

Rate each hazard on likelihood and consequence before controls, then again assuming the controls are actually in place. Two things fall out of this. First, you can see whether the controls earn their keep — if the band doesn't move, the controls are decorative. Second, the residual band tells the crew how much care the step still needs after everything you've planned.

JSA Generator scores on a 4-band matrix — Low, Medium, High, Extreme — and will not let a residual rating be worse than the rating before controls. An Extreme residual means the document is saying the work should not proceed as planned; that's a signal to change the plan, not a box to tick.

A worked example

One row from a trenching JSA, filled in the way the five steps produce it. The bands here are computed by the same matrix the product prints:

Read the controls column top to bottom: the trench box is the engineering control doing the actual work; the inspection and spoil setback are administrative; the hard hat is what's left. That ordering is the point.

Five mistakes that get JSAs handed back

• Generic steps. A JSA that would fit any trench on any site describes none of them.
• PPE as the whole control column. See above — it reads as "we didn't think about it".
• Written after the work started. The date and the crew signatures tell the story; a JSA signed at lunchtime for work that began at seven is worse than none.
• Never updated when conditions changed. Rain, a different machine, a new crew — the analysis was for different conditions.
• Nobody signed it. An analysis the crew never saw protects nobody and proves nothing.

Also worth reading: What is a JSA? · OSHA requirements for a JSA · Hazard scoring and the risk matrix