HAZOP Chair vs. Scribe: Roles, Qualifications, and Day Rates
Every facilitated HAZOP has two professional roles at the front of the room: the chair (facilitator, study leader) and the scribe (recorder, secretary). Buyers routinely under-specify the second role — and it shows up later as a worksheet nobody can defend to an auditor.
What the chair actually does
The chair owns the process of the study, not its technical conclusions:
- Before: scopes the study, defines nodes, sets guideword conventions, audits the process safety information, and refuses to start until drawings are study-ready.
- During: drives the guideword-by-guideword examination, keeps discussion on the causes-consequences-safeguards rail, draws out quiet team members, shuts down design debates, and paces the room — the difference between 2 and 4 nodes a day is mostly chairing skill.
- After: drafts the report, frames recommendations so they’re closeable (specific, assigned, verifiable), and runs the close-out review.
The skill is facilitation under technical load: the chair must know enough to smell a missing scenario, while staying independent enough to challenge the design without owning it.
What the scribe actually does
The scribe owns the record — and the record is the deliverable. Years later, the worksheet is what an incident investigation or regulator reads. A good scribe:
- captures the team’s reasoning in engineering language, not fragments (“high level in V-101 due to LV-101 failure closed; overflow to flare via PSV-105” — not “level issue, PSV ok”);
- keeps pace with the room in the PHA tool (PHA-Pro, PHAWorks, exSILentia, or an Excel template) without stalling discussion;
- flags inconsistencies live — the same safeguard credited twice, a consequence recorded without a cause;
- produces a worksheet that a person who wasn’t in the room can follow.
Scribing is not typing. A scribe who can’t follow the process discussion produces a record of what was said, not what was meant — and those diverge exactly where it matters.
Why one person can’t do both
For anything beyond a small, single-node review, a combined chair-scribe fails in one of two directions: facilitation stalls while the record catches up (you’re paying eight people to watch someone type), or the record thins while facilitation continues (you’re accumulating audit risk). Standards guidance and virtually all experienced practitioners treat separate chair and scribe as baseline for full studies. Treat a combined-role quote for a multi-day study as a red flag — or at least as a schedule 30% longer than quoted.
Qualifications to look for
| Chair | Scribe | |
|---|---|---|
| Core skill | Facilitation under technical load | Fast, precise technical capture |
| Typical background | Senior process/process-safety engineer | Process engineer or dedicated PHA technician |
| Formal signals | IChemE HAZOP leader training, CCPS courses, documented study log | PHA software proficiency, study log |
| Experience floor | 10+ studies chaired, ideally cross-industry | 5+ studies scribed in your tool of choice |
| Independence | Must be independent of the design | Helpful but less critical |
What each should cost
Scribes typically price at 40–60% of the chair’s day rate. Two structural notes:
- Don’t cheap out asymmetrically. A premium chair with a bargain scribe produces brilliant discussions recorded badly — the worst value combination in the market.
- Consider the firm-plus-independent mix. A common pattern: independent senior chair, scribe supplied by a firm with strong PHA-tool discipline. You get seniority where it matters and process where it matters.
Some teams train an internal engineer as scribe. It works — with a real caveat: the internal scribe must be released from their day job for the full study plus worksheet cleanup, and they need genuine tool training first. A distracted, untrained internal scribe is more expensive than a hired one; a good internal scribe is also your best future PHA coordinator.
Full study-cost math — day rates, node throughput, and worked examples — is in What Does a HAZOP Study Cost?. And the directory lists firms and independents by the services they offer, chairs and scribes included.