What is Texas RRC Rule 36?

Texas Railroad Commission Statewide Rule 36 (16 TAC §3.36) governs oil and gas operations involving hydrogen sulfide in Texas. It requires operators to calculate the Radius of Exposure for wells and facilities handling gas with H2S, submit contingency plans when the ROE reaches populated areas, and maintain specific safety equipment and training standards. It is the primary H2S regulation for Texas operations, including the Permian Basin Texas side.

What is the Rule 36 formula for 100 ppm ROE?

The 100 ppm ROE formula under 16 TAC §3.36 is: x = [(1.589)(mole fraction H2S)(Q)]^0.6258, where x is the radius in feet, mole fraction H2S is the decimal H2S concentration in the escaping gas, and Q is the maximum volume of gas available for escape in cubic feet per day at standard conditions. The 500 ppm ROE uses a coefficient of 0.4546 instead of 1.589, with the same exponent.

When is a contingency plan required under Rule 36?

Rule 36 requires a contingency plan when the 100 ppm radius of exposure reaches a public area — including dwellings, roads, churches, schools, parks, or other places of assembly. The specific triggers depend on the proximity to populated areas and the magnitude of the ROE. Operators must file the contingency plan with the RRC and coordinate with local emergency responders.

What counts as Q — the escape volume?

Q is the maximum volume of gas that could be available for escape at standard conditions (cubic feet per day). For gas wells, this is typically the 24-hour absolute open flow (AOF) rate. For producing wells and facilities, it's the daily production rate. For pipelines, it's the maximum throughput. The appropriate Q value depends on the equipment and operation being evaluated — consult a qualified engineer for site-specific determination.

Does the ROE calculation account for wind and topography?

No. The Rule 36 formula is a simplified planning tool that does not incorporate wind speed, atmospheric stability, or topographic effects. For detailed emergency response planning, operators use dispersion models like ALOHA, SLAB, or CALPUFF that account for meteorology. The Rule 36 ROE is the regulatory starting point for determining when more detailed modeling and contingency planning are required.

What are the OSHA exposure limits for H2S?

OSHA's permissible exposure limits for hydrogen sulfide are: acceptable ceiling concentration of 20 ppm, acceptable maximum peak of 50 ppm for up to 10 minutes per 8-hour shift, with no other measurable exposure at the peak concentration. The ACGIH TLV-TWA is 1 ppm and the STEL is 5 ppm. The IDLH (Immediately Dangerous to Life or Health) concentration is 100 ppm — hence the 100 ppm ROE threshold in Rule 36.

Does New Mexico have a similar H2S rule?

Yes. The New Mexico Oil Conservation Division (OCD) has its own H2S rules (19.15.11 NMAC) that are similar in principle to Texas Rule 36 but with some differences in formulas, triggers, and contingency plan requirements. Operators in the New Mexico side of the Permian Basin should reference the OCD rules directly. This calculator uses the Texas RRC formula, which is commonly adapted for planning in both jurisdictions but is not a substitute for actual NM OCD compliance.

What safety equipment is required for sour operations?

At a minimum: personal H2S monitors for all workers, fixed H2S detection at key equipment, SCBA (self-contained breathing apparatus) or supplied-air respirators staged at the worksite, wind direction indicators, evacuation alarms, and a documented muster point upwind of the potential release. All personnel entering the area require current H2S training per ANSI Z390.1. A written H2S safety program is required under OSHA's General Duty Clause 5(a)(1) and under Rule 36 for covered operations.

Can I rely on this calculator for actual compliance?

No. This calculator is a planning estimate only. Actual compliance with RRC Rule 36, OSHA H2S requirements, and NM OCD rules requires a qualified engineer or safety professional to perform site-specific assessment, verify inputs against authoritative gas analysis data, and sign off on contingency plans. Use this tool for initial planning, to understand what the formula produces for typical scenarios, and as a starting point for engineering consultation.

H2S Radius of Exposure Calculator

Estimate the 100 ppm and 500 ppm hydrogen sulfide radius of exposure for sour oil and gas operations using the Texas Railroad Commission Statewide Rule 36 formula (16 TAC §3.36). Used for initial planning, setback assessment, and contingency-plan scoping in the Permian Basin and other sour regions. For planning purposes only — not a substitute for a qualified engineer's contingency plan or dispersion model.

100 ppm = IDLH threshold

500 ppm = contingency zone

Permian Basin regulation

H2S Radius of Exposure Calculator

Estimate the 100 ppm and 500 ppm H2S radius of exposure using the Texas Railroad Commission Statewide Rule 36 formula (16 TAC §3.36). For planning purposes only — not a substitute for a licensed contingency plan or dispersion model.

Planning estimate only. This calculator uses the RRC Rule 36 formula for initial planning. Real contingency planning for sour operations must be performed by a qualified engineer with site-specific meteorological, topographic, and release-rate data. This is not legal or engineering advice.

H2S Concentration Unit

H2S in Gas Stream

From your gas analysis

Escape Volume (cubic ft/day)

Max available for escape (AOF or production rate)

Formula (Texas RRC Rule 36, 16 TAC §3.36): ROE = [coefficient × mole_fraction_H2S × Q]^0.6258, where coefficient = 1.589 for 100 ppm and 0.4546 for 500 ppm, and Q is the escape volume in cubic feet per day at standard conditions. Verify site-specific applicability with a qualified engineer.

Rule 36 Formula Explained

100 ppm ROE = [1.589 × mole fraction H2S × Q]^0.6258

500 ppm ROE = [0.4546 × mole fraction H2S × Q]^0.6258

Mole Fraction H2S

Decimal fraction of H2S in escaping gas (e.g., 5% = 0.05). From your gas analysis.

Q (Escape Volume)

Cubic feet per day at standard conditions. Typically AOF rate for gas wells or daily production rate.

Example: A gas well with 5% H2S and 5,000,000 cubic feet/day escape volume produces a 100 ppm ROE of approximately 3,191 feet (0.60 miles) — well into public-protection territory. The 500 ppm ROE is approximately 1,458 feet.

When You Need to Calculate ROE

Before Drilling Sour Wells

Required during well permitting for any location expected to encounter H2S. The ROE drives setback requirements and contingency plan scope.

Production Facility Planning

Tank batteries, separators, and flow lines handling sour gas require ROE assessment for each release scenario and each piece of equipment.

Rule 36 full text

The complete Texas Administrative Code 16 TAC §3.36 is available on the Texas RRC website. Always reference the current authoritative version for compliance decisions.

Don't Stop at the ROE — Document the Whole Program

The ROE is one piece of H2S compliance. OSHA and the RRC also require a written H2S safety program, SCBA-equipped personnel, monitoring, training records, and a contingency plan. BasinCheck gives you the written program template and the documentation system to prove it's in place.

Written Program

Free H2S safety program template aligned with ANSI Z390.1 and OSHA General Duty Clause 5(a)(1).

Training Records

Track H2S training, monitor certifications, SCBA fit-test dates, and refresher requirements.

Inspection Logs

Document atmospheric monitoring, equipment checks, drills, and corrective actions.

Free H2S Program Template H2S Drill Builder

H2S Radius of Exposure FAQ

Common questions about H2S ROE calculations and Texas RRC Rule 36

The Radius of Exposure is the horizontal distance from a potential H2S release point at which hydrogen sulfide concentrations in ambient air would equal a specified threshold — typically 100 ppm (the public protection zone) and 500 ppm (the contingency action zone). It's used by regulators and operators to plan sour-well operations, determine setback distances, and trigger contingency planning requirements.

Sour Operations Need Sharp Documentation

BasinCheck gives you the written programs, training records, and inspection logs that operators, OSHA, and the RRC expect for H2S operations.

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H2S Radius of Exposure Calculator

Rule 36 Formula Explained

When You Need to Calculate ROE

Before Drilling Sour Wells

Production Facility Planning

Rule 36 full text

Don't Stop at the ROE — Document the Whole Program

Written Program

Training Records

Inspection Logs

H2S Radius of Exposure FAQ

What is the H2S Radius of Exposure (ROE)?

What is Texas RRC Rule 36?

What is the Rule 36 formula for 100 ppm ROE?

When is a contingency plan required under Rule 36?

What counts as Q — the escape volume?

Does the ROE calculation account for wind and topography?

What are the OSHA exposure limits for H2S?

Does New Mexico have a similar H2S rule?

What safety equipment is required for sour operations?

Can I rely on this calculator for actual compliance?

Sour Operations Need Sharp Documentation