SWR 36 · 19.15.11 NMAC · API RP 55

The Inspector Won’t Ask If You Have H₂S. He’ll Ask For The Radius And The Plan.

Sour gas on the lease is not the finding. The finding is a radius of exposure nobody has recalculated since the last gas analysis, a contingency plan two revisions behind the call list, and a drill record that stops eighteen months ago. All three sit in different places until the day somebody asks for them together.

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One-time payment · works offline on a phone · nothing leaves your device

Three triggers. Any one of them
makes the plan mandatory.

Texas and New Mexico word it differently but arrive at the same place: a written H₂S contingency plan is compelled when the radius of exposure reaches people. The radius is not a judgement call, it is an equation, and the answer changes every time the gas analysis or the escape volume changes.

Trigger one · public area
100 ppm

The radius reaches a dwelling

A house, a school, a church, a park, a business, any occupied structure inside the 100 ppm radius. The app takes the distance you enter and tells you whether it falls inside.

Trigger two · wells
3,000 ft

The radius alone is enough

For a well, a 100 ppm radius at or above three thousand feet requires a plan whether or not anything is inside it. The app applies this to wells and correctly leaves it off facilities.

Trigger three · public road
500 ppm

The road inside the tighter radius

The 500 ppm radius is the one that governs public roads, and it catches locations that clear the first two comfortably. It is the trigger most often missed.

A calculation done once is a snapshot.
Compliance is a state you have to hold.

Both radii, with the working shown

Enter the H₂S concentration and the volume available to escape and the 100 ppm and 500 ppm radii appear immediately, along with the mole fraction and the exponent that produced them. The figures can be checked against a certificate of compliance rather than taken on trust.

The verdict, not just the number

Each of the three triggers is judged separately and reported in plain words: which one is met, by how much, and what distance it was measured against. A location that clears all three says so, and says what would change that.

📅

The plan goes stale on its own

A plan carries an issue date and a review interval, so it turns overdue without anyone remembering to check. Tick a revision trigger — the call list changed, a new dwelling went up, the gas analysis was redone — and it reads as out of date immediately, whatever the review date says.

📞

The call list is part of the plan

Person in charge, the twenty-four hour line, the regulator, the hospital, the National Response Center. Held in call order, dialled straight from the phone, printed with the plan, and flagged the moment an entry has no number against it.

Built for a phone at the gate of a sour location.

H₂S Contingency Plan & ROE Tracker
ROE calculatorSites & plansCall listDrillsPrint
100 ppm radius of exposure
8,736
feet · governs public areas
500 ppm radius of exposure
3,992
feet · governs public roads
A written H₂S contingency plan is REQUIRED.
  • The 100 ppm radius of 8,736 ft reaches a public area 800 ft away
  • The 100 ppm radius of 8,736 ft is at or above the 3,000 ft threshold
  • The 500 ppm radius of 3,992 ft reaches a public road 400 ft away
Needs attention
Sour Ridge 3-11
Revision trigger outstanding: call list changed, public area or road changed.
update required
plan rev 3
Redbird 14-2H
Drill or training overdue by 47 days, due 6 Jul 2026
drill overdue
47d
An entry on the emergency call list with no phone number against it is reported as an open item, not quietly ignored.

The same closed form both states publish.

The radius of exposure comes from the Pasquill-Gifford dispersion form printed in Texas Railroad Commission Statewide Rule 36 and New Mexico OCD 19.15.11 NMAC, and consistent with the methodology in API RP 55. The mole fraction is the ppm figure over a million, the escape volume is converted to cubic feet per day, and the constant changes between the hundred and the five hundred. Every one of those intermediate numbers is shown on screen, so the result can be reconciled with whatever a consultant or a state form says rather than argued with.

How a site reads on the register

Each site carries one status, worked out from its own radii and its own plan clock.

  • Below trigger — none of the three triggers is met on the current figures. No plan is compelled by the radius rule.
  • No plan — a trigger is met and no contingency plan is recorded against the site. This sorts to the top of the list.
  • Update required — a revision trigger is ticked, so the plan is out of date regardless of its review date.
  • Review due — the review date falls within thirty days. It appears before it becomes a finding.
  • Current — plan on file, no outstanding revision trigger, review date still ahead.

What the plan sheet carries

Site identity
Well or facility name, API or permit number, and which of the two it is — the 3,000 ft trigger only applies to wells.
Gas figures
H₂S concentration in ppm and the maximum volume available to escape, in MCF, MMCF or plain cubic feet per day.
Both radii
100 ppm and 500 ppm, in feet, with the mole fraction and escape volume that produced them.
Distances
Nearest public area and nearest public road, each judged against the radius that governs it.
Requirement verdict
Required or not, and the status of each of the three triggers individually, written out.
Plan record
Reference and revision, issue date, review interval, next review due, and the four revision triggers.
Emergency call list
Name, role, primary and alternate number, in call order, with missing numbers marked.
Training and drills
Date, type, who conducted it, headcount attending, and the next-due date each record sets for itself.

Works with no signal

A sour location forty miles out has no bars, and that is exactly where the plan gets read. Everything runs on the device, offline, once the page has been opened.

Install it like an app

Add to home screen on a phone or tablet and it opens full screen. No browser bar, no account, no login to remember at six in the morning.

Light by default

High contrast for a screen in direct sunlight, with a dark theme a tap away for a night shift. It remembers which you picked.

Your data stays yours

No account, no server, no sync. Everything lives in your browser storage, backs up to a JSON file, and exports to CSV whenever you want it elsewhere.

One caveat worth stating plainly. This computes and records — it does not write your contingency plan and it is not a substitute for a state-specific certificate of compliance or the judgement of whoever signs it. What it gives you is the radius, the verdict against the three triggers, and a record of the plan, the call list and the drills that stays current as you go rather than being assembled the week before an inspection.

One payment. Yours to keep.

$19
One-time purchase · no subscription · no account
  • Unlimited wells, facilities and plan records
  • 100 ppm and 500 ppm radius of exposure, with the working shown
  • Requirement verdict against all three regulatory triggers
  • Plan currency tracking with four revision triggers
  • Ordered emergency call list, tap to dial, prints with the plan
  • Training and drill log with per-record next-due dates
  • One-page plan sheet, CSV exports and a full JSON backup
  • Installs to the home screen and runs offline
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Works in any modern browser on a phone, tablet or desktop. No refunds. All sales are final.