When your storage tank holds sour product, vapor control is not a step you schedule after the maintenance window opens. It is a permit requirement and a crew safety obligation that has to be in place before the first fitting comes loose. Dallas area terminals and chemical plants handling sour crude, sour water, or any product stream carrying H2S face requirements under both TCEQ Chapter 115 and OSHA confined space rules that apply simultaneously, and the equipment configuration that satisfies both depends on what is actually in your vapor stream.
The wrong control device produces a permit deviation on your compliance record. The wrong pre-job review puts your crew in an H2S atmosphere without adequate protection. We have been deploying mobile H2S vapor control for terminals and chemical plants across Texas since 1992, and here is exactly what Dallas facilities need to know before the next sour tank job starts.
What Sour Means Under TCEQ Rules and Why Dallas Facilities Are Directly Affected
TCEQ defines sour gas as any stream containing more than 1.5 grains of H2S per 100 cubic feet, which equals approximately 24 parts per million under standard conditions. Once your stream meets or exceeds that threshold, your facility falls under increased regulatory requirements that go beyond standard VOC control obligations under Chapter 115. Every owner and operator is responsible for confirming whether that threshold applies to their site and for keeping current H2S concentration data to support their compliance position.
Dallas County sits within the Barnett Shale area counties covered by 30 TAC 106.352. Facilities in Dallas that handle sour gas and were constructed or modified after April 1, 2011 must comply with the full requirements of subparts (a) through (k) of that rule. Those requirements include a documented maintenance plan, a leak detection and repair program, specific control equipment obligations, and mandatory TCEQ registration before sour gas operations begin. Any site where a stream reaches or exceeds 24 ppm H2S must also maintain a site-specific H2S gas analysis no older than two years. TCEQ does not accept outdated analysis as a valid compliance demonstration.
Those Barnett Shale requirements apply alongside the new TCEQ Chapter 115 rules that took effect January 1, 2025, covering all ten DFW nonattainment counties including Dallas. Fixed roof tanks storing VOC at true vapor pressures at or above 1.5 psia require a vapor control system. Degassing emissions must route to a permitted control device from the moment product removal begins. For a Dallas facility handling sour product, both sets of requirements apply simultaneously, and your vapor control setup must satisfy both before work starts.
Why H2S in Your Vapor Stream Changes the Equipment Decision
The regulatory requirements above explain what your permit demands. What follows explains why H2S specifically changes the equipment configuration required to meet those demands.
Under OSHA 29 CFR 1910.1000 Table Z-2, the general industry ceiling for H2S is 20 ppm. A peak of 50 ppm is permitted for no more than 10 minutes in a shift only when no other measurable H2S exposure has occurred. Most facilities and contractors set crew withdrawal alarms at 10 ppm to give workers adequate time to respond before reaching the regulatory ceiling. At 100 ppm, NIOSH classifies H2S as immediately dangerous to life or health. The vapor space above a sour crude or sour water tank routinely holds concentrations well above those thresholds, which is why vapor control must be operating before any fitting on the tank is opened.
Under OSHA 29 CFR 1910.146, atmospheric testing is required before crew access to any space where H2S may be present. Continuous ventilation must run throughout the work. H2S concentrations must be reduced to acceptable levels before anyone works near an open tank connection. These requirements apply regardless of schedule pressure or job urgency.
The equipment problem specific to H2S is straightforward. A thermal oxidizer destroys VOCs through high-temperature combustion, but when it combusts H2S, the reaction produces sulfur dioxide. If the H2S loading in your vapor stream is high enough, the SO2 produced exceeds your permit’s sulfur emission limits and you end up with a second permit violation while attempting to resolve the first. The correct approach for sour streams is to stage a liquid scrubber upstream of the thermal oxidizer to strip the H2S from the vapor before the remaining VOC-containing gas reaches the combustion chamber. That sequencing is what keeps your control device operating within your permit conditions throughout the job.
What Your TCEQ Permit Requires Before Vapor Control Equipment Goes on Your Dallas Tank
TCEQ Chapter 115 Subchapter B Division 1 governs vapor control requirements for storage tanks in the Dallas area based on your stored product’s true vapor pressure and tank configuration. For degassing operations, the control device must achieve the destruction or removal efficiency your permit specifies. All emissions must route to that permitted device from the start of product removal, without exception.
For sour operations in Dallas County under 30 TAC 106.352, your facility must document the H2S concentration of the stream being handled. The control equipment must meet the efficiency requirements for that specific stream. A site-specific H2S analysis older than two years does not satisfy the ongoing compliance demonstration requirement.
Three Things to Confirm Before the Job Starts
Three items must be confirmed before product removal begins on a sour tank job in Dallas. The control device on site must match what your permit authorises, including its rated destruction or removal efficiency. The H2S loading in your vapor stream must be within the range the control device can handle without producing SO2 at levels that breach your sulfur emission limits. The contractor’s OQ-qualified technicians must have reviewed your permit conditions and vapor stream composition before the first connection is made. Confirming those three items before startup is what keeps a sour tank job compliant from the first minute to the last.
How We Configure and Operate Mobile Vapor Control on a Sour Tank Job in Dallas
We connect and verify the vapor control system before product removal or venting begins. The system draws vapor from the tank under negative pressure, keeping the tank under a slight vacuum throughout the job. Any leak in a connection draws air inward rather than allowing vapor to escape, which is the safer operating configuration our technicians establish as standard practice on every job.
The Equipment Configuration We Use for Sour Streams
For sour streams, we stage a liquid scrubber ahead of a thermal oxidizer. The scrubber uses our VapoScrubH2S chemistry to neutralise H2S and strip it from the vapor stream before the remaining VOC-containing gas passes to the thermal oxidizer for destruction. That sequencing keeps the control system operating within your permit conditions throughout the job. For details on the scrubbing systems we deploy at Dallas area terminals and chemical plants, see our vapor scrubbing and odor control services in Dallas.
How We Manage H2S Safety Throughout the Job
Our OQ-qualified technicians monitor H2S concentrations continuously using calibrated personal gas detection equipment and fixed-point monitors at the connection area. The site safety plan prepared before the job starts identifies the H2S concentrations that trigger crew withdrawal, the confined space entry protocol if tank access is needed, and the respiratory protection required for each phase of the work. That plan is reviewed with your site EHS team before the first fitting is opened on every job. We have maintained a 0.0 TRIR safety record across more than 30 years of operations because that review does not get skipped.
Sour Tank Vapor Control Work We Have Completed in Texas
We have managed sour tank vapor control at terminals, chemical plants, and refineries across Texas on projects where the H2S concentration in the vapor stream required a scrubber and thermal oxidizer working in series before any product removal could begin safely. On each of those jobs, our team reviewed the facility’s air permit, confirmed the vapor stream composition, and had the control system connected and verified before the maintenance window opened. Operations stayed within permit limits throughout each project. For a detailed account of one of these projects, see our sour tank vapor control case study.
“The clients we work with on these jobs consistently tell us the same thing.
Envent has always provided trained, qualified, and knowledgeable personnel to perform their services. They have been able to respond to our requests for degassing services on an emergency basis.”
Terminal Engineer at Chevron
The Dallas Area Facilities We Serve and Where Else We Work
We work regularly with fuel storage terminals, chemical manufacturing plants, midstream pipeline terminals, and bulk liquid transfer facilities across the Dallas area. These are operations where sour product handling is part of a normal maintenance cycle, where TCEQ permit conditions are non-negotiable, and where a contractor who has not reviewed your permit or matched the right equipment to your vapor stream creates a compliance gap that outlasts the job. Beyond Dallas, we support facilities across the Texas Gulf Coast, Louisiana, California, the Midwest, and the Northeast. Our degassing and vapor control services cover the full range of what we deploy across different facility types and product streams.
Frequently Asked Questions
Does TCEQ require specific vapor control equipment for sour tank operations at Dallas area terminals and chemical plants?
Yes. TCEQ Chapter 115 requires vapors from Dallas area storage tanks to be routed to a control device meeting the destruction or removal efficiency in your air permit. For Dallas County facilities under 30 TAC 106.352 handling streams at or above 24 ppm H2S, additional requirements apply including TCEQ registration, current site-specific H2S documentation no older than two years, and control efficiency minimums for vents where H2S reaches that concentration. We review your permit before any equipment goes on your site.
What H2S concentration makes a tank stream sour under the rules that apply to Dallas facilities?
TCEQ defines sour gas as a stream containing more than 1.5 grains of H2S per 100 cubic feet, equivalent to approximately 24 ppm under standard conditions. Dallas County falls within the Barnett Shale area under 30 TAC 106.352, and facilities constructed or modified after April 1, 2011 that handle streams at or above that threshold fall under the full Barnett Shale Permit by Rule requirements, including control equipment obligations, a leak detection and repair program, and mandatory recordkeeping throughout operations.
Can a thermal oxidizer handle a sour vapor stream from a Dallas area storage tank without a liquid scrubber upstream?
No, not in most cases involving significant H2S concentrations. Thermal oxidation of H2S produces sulfur dioxide, and if the H2S loading in your vapor stream is high enough, the SO2 output breaches your permit’s sulfur emission limits while you are addressing your VOC compliance requirement. We stage a liquid scrubber ahead of the thermal oxidizer to remove H2S from the stream first, which allows the oxidizer to handle the remaining VOC content within your permit conditions without generating a secondary compliance problem.
What does OSHA require for crew safety during sour tank vapor control work at Dallas chemical plants and terminals?
OSHA 29 CFR 1910.146 requires atmospheric testing and continuous ventilation before and during crew access to any space where H2S may be present. The general industry ceiling under 29 CFR 1910.1000 is 20 ppm, and most Dallas area facilities set withdrawal alarms at 10 ppm to give crews adequate response time before reaching that limit. Every crew we send to a Dallas sour tank job carries calibrated H2S detection equipment, operates under a written confined space entry plan reviewed with your site EHS team, and knows the action levels requiring immediate withdrawal before the job begins.
How long does it take to get mobile vapor control equipment to a Dallas facility for a sour tank job?
Our Houston operations hub covers the Dallas-Fort Worth area with a planned mobilisation window of four to eight hours for projects coordinated in advance. For unplanned situations where a Dallas area tank needs to come out of service, call our 24-hour emergency line at 888-997-9465 and our team will confirm equipment availability and timing for your location.
Do you handle sour tank vapor control for both planned maintenance and emergency situations at Dallas facilities?
Yes. Most of the sour tank work we do in Dallas is planned in advance, which gives our team time to review your permit, confirm the vapor stream composition, and have the right scrubber and thermal oxidizer configuration in place before your maintenance window opens. We also respond to unplanned situations when a Dallas area tank needs to come out of service without advance notice, with the same permit review and equipment checks completed before work begins.
What should I ask a vapor control contractor before they come to my Dallas terminal or chemical plant for a sour tank job?
Ask whether their personnel hold current OQ qualifications. Ask whether their equipment is configured for the H2S concentration in your specific vapor stream and not just standard VOC degassing. Ask whether they have reviewed your TCEQ air permit and confirmed their control device meets your authorised destruction efficiency. Ask what H2S monitoring equipment they bring to site and what action levels trigger crew withdrawal. A contractor who cannot answer those four questions before arriving at your Dallas facility creates a compliance and safety risk your operation does not need.
Does the DFW Severe ozone nonattainment designation add requirements on top of the H2S rules for sour tank work in Dallas?
Yes. DFW was reclassified as a Severe nonattainment area under the 2008 eight-hour ozone standard in November 2022, and new TCEQ Chapter 115 rules that took effect January 1, 2025 added vapor control system requirements for storage tanks, degassing emissions, and vent gas streams across all ten DFW counties. Those rules apply alongside the H2S-specific requirements under 30 TAC 106.352 for Dallas County facilities, so a sour tank job in Dallas must satisfy both the VOC emission controls under Chapter 115 and the H2S control requirements under your permit at the same time.
What compliance records does our Dallas facility need to maintain after a sour tank vapor control job?
Your facility needs records showing the control method used, the product handled, the tank capacity, and throughput for the job. For sour operations in Barnett Shale counties including Dallas under 30 TAC 106.352, quarterly H2S concentration measurements are required. We provide compliance documentation for every vapor control job we perform, and our client reporting portal gives your team access to real-time project records with seven-year retention. To discuss your next sour tank job in Dallas, call 888-997-9465 or request a quote.
Talk to Our Team Before Your Next Sour Tank Maintenance Window in Dallas
If your next tank maintenance window in Dallas involves sour product, your vapor control plan needs to be confirmed before the job is scheduled. We carry the equipment, the OQ-qualified crew, and the permit knowledge to keep your project on schedule without putting your TCEQ compliance record at risk. We have been doing this work at terminals and chemical plants across Texas since 1992. To schedule a project or discuss an emergency response need, call 888-997-9465 or request a quote.
