We have managed H2S vapor control at Texas industrial facilities since 1992, working with refinery turnaround planners, EHS managers, and midstream terminal operators across the Gulf Coast and beyond. On every sour service project, the outcome depends on how the vapor stream is characterized before the job starts and whether the equipment deployed matches what is actually in that vapor space.
We operate the largest mobile fleet of vapor control equipment in North America, with our Texas hub carrying ESCRUB scrubber units, EMTOS and EMECS thermal oxidizers, blowers, and monitoring equipment built for Gulf Coast refining and chemical service. For project planning or emergency response, call 888-997-9465 or request a quote.
Why Does H2S Change How a Texas Maintenance Outage Gets Planned?
H2S vapor control is not a variant of standard hydrocarbon degassing. The hazard profile, the regulatory requirements, and the equipment configuration all change when H2S is present above trace levels, and treating it like a routine VOC job creates compliance failures, safety events, or both.
H2S is heavier than air, which means it settles and accumulates in low points, vapor spaces, and confined areas where ventilation is limited. A worker in a borderline H2S environment for several minutes can lose their ability to smell the gas before their monitor alarms, because H2S numbs your sense of smell at elevated concentrations. Continuous instrument monitoring is non-negotiable on any sour tank job in Texas for this reason, regardless of what the pre-entry reading showed.
The flammability range for H2S compounds the hazard. Its lower explosive limit is approximately 4 percent by volume, far above the toxic concentrations where personnel are already at risk. A vapor space with dangerous H2S levels is simultaneously a potential ignition source, which means your crew sequencing and hot work authorization procedures need to account for both hazards at once.
At the process level, the critical issue is what happens downstream when H2S reaches your control device without upstream treatment. Combusting sour vapor directly in a thermal oxidizer converts H2S to sulfur dioxide, a separately regulated air contaminant. At high enough inlet concentrations, the resulting SO2 load in the oxidizer exhaust can push your facility above air permit thresholds even when the thermal unit is operating at rated efficiency, which is why H2S characterization must happen before equipment is specified, not after the crew arrives on site.
What Does TCEQ Require for Sour Stream H2S Vapor Control in Texas?
How Does TCEQ Define a Sour Gas Stream and What Does That Trigger?
TCEQ requires a site-specific H2S gas analysis for any facility handling a stream with more than 24 ppm hydrogen sulfide, under 30 TAC Section 106.352. That figure corresponds to the TCEQ sour gas definition of more than 1.5 grains of H2S per 100 cubic feet. If your tank held sour crude, sour water, or a process stream from a unit in sour service, confirming whether your vapor crosses that threshold is one of the first steps in outage planning, because it determines which permit conditions apply to your vapor control method and documentation requirements.
For facilities in Dallas County and the other Barnett Shale counties under 30 TAC 106.352, quarterly H2S concentration measurements are required for qualifying sour operations, and any site-specific analysis used for permit compliance must be no older than two years. If your records are approaching that limit, a planned maintenance outage is the logical time to refresh them. Carrying stale H2S data into your next TCEQ compliance cycle creates a documentation gap that your permit reviewer will flag. The full requirements are available through the TCEQ sour gas handling compliance.
What Do Texas MSS Rules Require for Planned H2S Outage Events?
Texas Maintenance, Startup, and Shutdown rules require BACT-level vapor control for major planned maintenance activities where a compound has a vapor pressure greater than 0.50 psi and a volume greater than 10 cubic feet. Most sour tanks and process vessels at Texas refineries, terminals, and chemical plants meet both thresholds, which means your outage vapor control plan needs a documented control approach before the job opens. A general description is not sufficient for a TCEQ permit review.
Thermal oxidation devices can claim design destruction efficiency from 90 to 99.9 percent for VOCs and H2S depending on design and monitoring level, under 30 TAC 106.352. For a major source facility in Texas seeking to meet BACT at the 99.9 percent tier, the appropriate monitoring design and full operational documentation are required. Our thermal oxidizers operate at a minimum chamber temperature of 1,400 degrees Fahrenheit and are documented to meet that standard on every Texas deployment.
The TCEQ Chapter 115 rule updates that took effect January 1, 2025 tightened vapor control requirements for storage tanks and vent gas streams across Texas. If your facility’s permit was written before those changes, reviewing your current conditions against the updated rules before equipment is sized is worth the time.
How Do You Choose the Right H2S Vapor Control Equipment for Your Texas Outage?
What Determines Whether You Need a Scrubber, a Thermal Oxidizer, or Both?
Equipment selection depends on three factors: what is in the vapor stream, what volume you are moving, and what your TCEQ permit requires at the outlet. Getting one of those three wrong means your job either falls short on compliance or is built for conditions that do not match your site.
For low-to-moderate H2S concentrations combined with hydrocarbon vapors, a liquid scrubber deployed upstream of a thermal oxidizer handles the H2S removal first, then routes the conditioned stream to the oxidizer for final VOC destruction. This configuration keeps SO2 formation at the stack within your permit limits and gives your EHS team a documented treatment sequence for TCEQ review.
For streams that are primarily hydrocarbon with trace H2S at concentrations low enough that combustion will not generate a permit-exceedance SO2 load, a thermal oxidizer alone may be the right configuration. That determination requires actual vapor sampling data from your facility, not an assumption based on crude type or prior job history. If your stream involves higher H2S concentrations or mixed acid gas compounds, our liquid scrubber chemistry covers the VapoScrub H2S5 formulation we deploy for targeted hydrogen sulfide removal and the VapoScrub EX5 multi-purpose formulation for broader VOC and HAP treatment, along with the full range of ESCRUB configurations available for sour service.
Why the Treatment Sequence on a Sour Stream Job Cannot Be Reversed
The order of treatment on a sour stream project is determined by chemistry, not by preference. Running the thermal oxidizer first and the scrubber second does not produce the same result, because the objective is not to capture SO2 after it has formed. The objective is to prevent SO2 formation by removing H2S before any combustion stage.
In the correct configuration, vapor from the tank or vessel moves first to the liquid scrubber, where H2S is neutralized through chemical reaction with the VapoScrub media. The outlet from the scrubber still carries the hydrocarbon vapor load, but the H2S concentration has been reduced to a level where downstream combustion will not generate SO2 in excess of your permit limit. The thermal oxidizer then destroys the remaining VOC load at temperatures above 1,400 degrees Fahrenheit, delivering 99.9 percent destruction efficiency at the stack.
This two-stage configuration is what our degassing and vapor control service deploys for sour stream projects across Texas. Getting this sequence documented correctly in your pre-job plan gives your EHS team the compliance record needed for TCEQ review after the project closes.
What Does Sour Service Mean for Confined Space Entry Preparation on a Texas Maintenance Job?
Why a Single Pre-Entry Reading Is Not Enough on a Sour Tank Job
When a tank or vessel has held sour product, confined space entry preparation goes beyond the standard pre-entry atmospheric clearance test. H2S can rebuild from residual liquid in the tank bottom, from wall coatings, or from product that has migrated into structural recesses. Your initial reading is not a confirmation of what conditions will be at the work surface ten minutes into the job, which is why continuous atmospheric monitoring throughout the work period is both a regulatory requirement and an operational necessity.
Under OSHA 29 CFR 1910.146, any vessel that held sour product qualifies as a permit-required confined space. The standard requires atmospheric testing before entry, continuous monitoring during the work period, a written entry permit, an attendant stationed outside the space, and a documented non-entry rescue procedure. The OSHA permissible exposure limit for H2S in general industry is 20 ppm under 29 CFR 1910.1000 Table Z-2, and your vapor control system needs to hold ambient H2S below that level from the first draw of the degassing operation through final clearance.
Our OQ-qualified technicians operate under HAZOP and PHA safety reviews before any equipment is deployed on a Texas project. Site-specific safety plans for H2S jobs include continuous atmospheric monitoring protocols, full OSHA-compliant confined space procedures, and automatic safety valve systems that isolate vapor control equipment in the event of a process upset. You can review our safety record and field protocols to see how those requirements are documented and maintained across every project we run.
Our Recent Work at a Houston Area FCCU Turnaround With High H2S Vapor Streams
A Gulf Coast refinery needed turnaround support for their Fluidic Catalytic Cracking Unit across a depressurization and decontamination window of approximately six days. The unit had to depressure from 35 PSIG at 3,500 SCFM to bring the LEL concentration below 10 percent, with vapor streams carrying high H2S concentrations and temperatures up to 100 degrees Fahrenheit throughout the process.
We mobilized two EMECS-42 thermal oxidizers alongside an ESCRUB-6000 recirculating scrubber for H2S removal, with two KO pots and full safety equipment including an automatic safety valve to isolate both systems in the event of a process upset. The job completed two days ahead of the planned schedule with no safety incidents and full compliance documentation delivered to the client. Full project details are in our Houston area FCCU turnaround case study.
“Their state-of-the-art equipment definitely is the best in the business, and they always seem to be improving it. All of their operators are knowledgeable and problem solvers.”
Western Region tank Coordinator at Shell
Who We Work With on H2S Vapor Control Projects in Texas and Across North America
We serve the following facility types on H2S vapor control projects across Texas and throughout our North American service area:
- Petroleum refineries on the Texas Gulf Coast and inland handling sour crude, vacuum tower bottoms, and sour water stripper systems.
- Chemical and petrochemical plants across Dallas-Fort Worth, Beaumont, Port Arthur, and the Gulf Coast corridor with acid gas streams, sulfur recovery units, and process vessels in sour service.
- Midstream terminals and pipeline facilities in Texas handling sour crude transmission or natural gas with elevated H2S content.
- Industrial remediation sites across Texas where soil vapor extraction or groundwater treatment involves H2S-bearing vapor streams.
- Marine terminals loading sour crude barges and vessels requiring USCG-certified vapor recovery with H2S treatment.
Our Tier-1 client portfolio includes operators such as ExxonMobil, Shell, Chevron, Valero, Phillips 66, and Kinder Morgan, all of whom operate under strict Texas permit conditions and require documented safety performance on every project. Our work history across Texas Gulf Coast facilities covers both planned outages and emergency events, with refinery vapor control services in Dallas and vapor scrubbing and odor control in Dallas available for DFW-area facilities specifically.
Our Texas equipment stages from our Houston-area hub, which can reach DFW-area facilities within a 4 to 8 hour mobilization window for planned projects, with 24-hour emergency response available for unplanned events. Beyond Texas, we operate H2S vapor control projects across Louisiana, California, the Midwest, the Northeast, and Canada, with equipment staged at hub locations in Southern California, Northern California, New Jersey, Louisiana, Utah, and Indiana.
Frequently Asked Questions
Does my Texas facility need an upstream scrubber if the tank only held sour crude at moderate H2S concentrations?
Yes, if the H2S concentration in the vapor space will produce a SO2 load at the oxidizer stack that exceeds your air permit limit, a scrubber needs to be upstream of the thermal oxidizer. The only way to confirm whether that threshold is crossed is actual vapor sampling from your tank before equipment is sized.
What documentation does TCEQ require for H2S vapor control during a planned maintenance outage in Texas?
Yes, Texas MSS rules require BACT-level vapor control with documented compliance for planned maintenance events where compound vapor pressure and volume meet the major activity thresholds. For sour service, that typically means a thermal oxidizer at 99.9 percent destruction efficiency with upstream scrubber treatment if H2S concentrations would otherwise produce a permit-exceedance SO2 load.
Can a thermal oxidizer handle an H2S stream directly at a Texas facility without a scrubber upstream?
Yes, at low H2S concentrations a thermal oxidizer alone may be the right configuration. At higher concentrations, the correct approach is liquid scrubber treatment first, then thermal oxidation for final VOC destruction. Which applies to your project depends on your vapor composition and what your TCEQ permit allows at the stack.
What OSHA standards apply to confined space entry on a sour tank maintenance project in Texas?
Yes, OSHA 29 CFR 1910.146 applies to any vessel that held sour product at a Texas facility, requiring atmospheric testing before entry, a written entry permit, continuous monitoring during the work period, and a documented rescue procedure. Our site-specific safety plans for Texas sour service jobs are built around these requirements before any crew steps on site. Marine terminals and vessels in the Dallas area can review our marine vapor control and degassing services in Dallas for USCG-certified requirements that apply to their operations.
How early should a Texas facility engage a vapor control contractor for a planned H2S maintenance outage?
Yes, earlier is better, particularly for multi-vessel outages where you have simultaneous sour streams requiring phased equipment deployment across your Texas site. Confirming H2S concentration data, sizing equipment correctly, developing the site-specific safety plan, and pre-positioning assets all take time that cannot be recovered once the outage window opens. Midstream terminals and pipeline facilities in the Dallas area can review our midstream vapor control services in Dallas for mobilization details specific to their operations.
Does the scrubber-oxidizer sequence matter on every H2S vapor control job in Texas, or only for high-concentration streams?
Yes, the sequence matters on every sour stream job in Texas where H2S combustion could generate SO2 above your permit limit, regardless of whether your inlet concentrations are classified as moderate or high. The threshold that determines whether upstream scrubbing is required is not just the H2S inlet concentration but what that concentration produces at the oxidizer stack relative to your TCEQ permit conditions.
What compliance documentation does Envent provide after an H2S vapor control project in Texas?
Yes, full compliance documentation is provided through our eReport client portal, where records are retained for seven years and accessible in real time throughout the project. Documentation includes destruction efficiency data, equipment operating logs, atmospheric monitoring records, and safety plan compliance records for TCEQ review, permit renewal, and internal reporting.
Who at a Texas facility should be involved in scoping an H2S vapor control job before the outage begins?
The most complete picture comes from involving your EHS manager, turnaround planner, and operations team together early. Your EHS manager knows your permit conditions and what your control device must achieve at the stack. Your turnaround planner knows the outage schedule and vessel history, and operations knows the last product in the tank and any process conditions that may have affected vapor composition. Call our team at 888-997-9465 or schedule a conversation before your outage window opens.
Talk to Our Team About Your Next H2S Outage in Texas
We work with EHS managers, turnaround planners, and operations teams across Texas to build H2S vapor control plans that fit the actual conditions at your facility. To schedule a project discussion or discuss an emergency response need, call 888-997-9465 or request a quote.
