What counts as an Ex-rated item?

Anything in the certification dossier that needs a marking or an evidence entry: instruments, enclosures, junction boxes, heaters and cable glands. An assembly certified as a unit counts as one item.

Where does the documentation rate come from?

From closed packages: divide the items in the dossier by the engineering hours the work actually took. Refresh the rate when the item mix changes.

Why add a review, hold, and rework allowance?

First-pass dossiers rarely clear review untouched. Holds, queries and corrections add time on top of documentation, so the allowance covers that work instead of hiding it in a schedule.

Does the hazardous-area zone change the labor?

Only through the dossier, because a Zone 0 or Zone 1 package usually carries more evidence per item than a Zone 2 package. The hours follow the item count and the rate you enter.

Oil, Gas & Energy Equipment Manufacturing calculator

Hazardous-Area Certification Burden Calculator

Estimate certification labor from the Ex-rated item count and a documentation rate, then add a review, hold, and rework allowance. The total is compared with the engineering hours you have available.

What this calculator does

Certification labor for Ex-rated equipment from an item count, a documentation rate and a review allowance, checked against available hours.

Formula used

Base certification time = Ex-rated items to certify ÷ certification documentation rate
Allowance hours = base certification time × review, hold, and rework allowance ÷ 100
Required certification labor = base certification time + allowance hours
Engineering shortfall = MAX(required certification labor − available engineering hours, 0)

Inputs explained

Ex-Rated Items to Certify: Instruments, enclosures and assemblies needing certification evidence.
Certification Documentation Rate: Items cleared per engineering hour, from closed certification packages.
Review, Hold, and Rework Allowance: Review, hold and rework time as a share of base documentation hours.
Available Engineering Hours: Engineering hours one reviewer can give this package.

How to use the result

Best suited to sizing certification labor for a zone 1 skid, deciding if a second reviewer is needed, quoting documentation effort on an ex order.
Third-party reviews and notified body waits sit outside this estimate. No gas volume, pressure or standard-to-actual condition conversion enters this labor model. An allowance does not cover a dossier restart after a design change.

Current U.S. benchmarks

Industrial electricity averages 9.77 cents per kWh across the U.S. (EIA, Jul 2026), up 4.7% from a year earlier. Energy-intensive steps carry this directly into unit cost.
Steel mill PPI stands at 381.162 (BLS, Aug 2026), up 23.4% from a year earlier. New factory orders are up 8.5% year over year (Census).

Common questions

What counts as an Ex-rated item? Anything in the certification dossier that needs a marking or an evidence entry: instruments, enclosures, junction boxes, heaters and cable glands. An assembly certified as a unit counts as one item.
Where does the documentation rate come from? From closed packages: divide the items in the dossier by the engineering hours the work actually took. Refresh the rate when the item mix changes.
Why add a review, hold, and rework allowance? First-pass dossiers rarely clear review untouched. Holds, queries and corrections add time on top of documentation, so the allowance covers that work instead of hiding it in a schedule.
Does the hazardous-area zone change the labor? Only through the dossier, because a Zone 0 or Zone 1 package usually carries more evidence per item than a Zone 2 package. The hours follow the item count and the rate you enter.

Last reviewed 2026-10-01.