Advice - Our Knowledge, Your Success | Envent Corporation

We don’t just lead the industry in safety and compliance – Envent transforms by leadership and continuous improvement in equipment, personnel training innovation and processes.   Creating a knowledge base from our specialist experience for our customers and potential customers is our way of giving back and ensuring that every project has the opportunity to be cost-effective without sacrificing safety or compliance.

Envent Corporation | Degassing Basics

Envent performs a niche service in the refinery, midstream, and petrochemical sector. Our work is highly specialized. And our engineering team spends 75% of their time innovating and engineering new ways to perform your work safer, more efficient and cost effective.  Envent provides both the turnkey service and rental of our specialty vapor control equipment.  We perform tank, vessel, ship, barge and pipeline degassing and vapor control services using thermal oxidizers, IC engines, passive and counterflow vapor scrubbers, flares and granular media vapor scrubbers.

Degassing is defined as the removal of hydrocarbon toxic, explosive, noxious, or odorous vapor from a vessel, tank, pipeline under vacuum or pressure and controlling that vapor through chemical reactions, oxidation at high temperatures to water vapor and carbon dioxide as well as absorption and adsorption using chemicals and media.  Vapors are removed from vessel, tank, pipeline, ship, barge or soil using a blower or if the system is under existing pressure directly in to the vapor control unit.  Units are mobile or skid mounted.  Toxic or nuisance vapors are controlled for reasons of compliance, exposure, safety or nuisance.  Envent degassing is done using our proprietary systems which we have spent over 20 years perfecting.  And we still continue to innovate and improve our processes to benefit you, the customer.

In addition to engineering and designing the right systems for your project, the Envent engineering team and compliance personnel obtain regulatory permits, when necessary, and maintain compliance documentation for all projects and customers.  Envent also markets various media for the neutralization, absorption, or adsorption of various industrial vapor streams, including liquid chemistries, granular activated carbons (made of coal, coconut shell, and specialty media).  We engineer and fabricate all of our own vapor scrubbers and degassing systems.  Envent will use highly skilled and trained operators.  Systems may be customized units for a specific application or standard out of our fleet of Envent vapor control systems.

Envent works for most major oil companies, refineries, chemical plants, pipelines, terminals and various maritime related companies as well as many service companies in their process vapor control compliance needs.

Tank degassing:

  • Controls toxic and harmful air contaminants in order to reduce the emission of air pollutants.
  • Minimizes human exposure to hazardous pollutants.
  • Strives to eliminate the risk of explosion during tank cleaning or tank repair

Different state and federal regulations address these health and safety issues.

In most cases the refinery or chemical plants will have Title V (MSS) permits that require they control to 5,000 ppmv.

Example: Texas Commission on Environmental Quality (TCEQ) degassing regulation calls for a reduction of tank vapors to less than 34,000 ppmv.

These regulatory requirements are even more stringent in California. For example, the Bay Area Air Quality Management District (BAAQMD) calls for a tank vapor concentration reduction to 5,000 ppmv as methane. The South Coast AQMD requires that we degas to 5,000 ppmv and hold it for 1 hour and control vapors from vacuum trucks being used on tank degassing projects to 500 ppmv.

  • All districts where petroleum storage tanks are located in California require degassing. The California degassing rules include Bay Area Air Quality Management District (BAAQMD) Regulation 8
  • South Coast Air Quality Management District (SCAQMD) Rule 1149
  • Ventura Air Pollution Control District (VAPCD) Rule 74.27, and
  • San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD) Rule 4623.
  • Pipeline and vacuum truck vapor control is also becoming regulated.
  • Marine degassing is strictly regulated under the USCG
  • National Emission Standard for Hazardous Air Pollutants (NESHAP) is more strictly enforced than at any time since its inception.  All abatement systems must have a minimum of 98% destruction efficiency.

Let Envent clearly outline the process for potential customers:

  • The size of a tank degassing job is largely determined by tank geometry, tank size, product stored, vapor pressure of product, amount of residual product after stripping, and the amount of sludge at the tank bottom.
  • Because of the danger of explosion, all potential ignition sources must be completely eliminated.

In a typical degassing process:

  • Vapors are extracted from the tank in question and into a degassing unit. Air is introduced into the tank.
  • The tank vapor is initially rich enough to be above the upper explosive limit (UEL) before degassing.
  • As the tank vapor is diluted with air, it goes though the explosive domain before dropping below the lower explosive limit (LEL). In some cases, an inert gas such as nitrogen is used initially instead of air to eliminate the danger of explosion – particularly if pyrophoric iron or other ignition sources could be present.
  • Vapor control is curtailed once the storage tank roof is floating and the vapor space is eliminated.

Tank degassing is also used, in some areas, during a refilling operation. As volatile liquid products, such as gasoline, are introduced into an empty tank, they will flash and generate vapor. As additional liquid is pumped into the tank, hydrocarbon vapors in the vapor space will compress and release into the atmosphere. Since gasoline vapors contain many hazardous air pollutants, degassing during most refilling operations is required to eliminate these emissions.

There are a number of methods that have been used to perform degassing – read below for a brief definition of each.

  • EMTOS – Envent Mobile Thermal Oxidizer System – is > 99.9% efficient
  • Thermal Combustion Units –These units don’t meet the criteria to be labeled “thermal oxidizers”  and don’t sustain 1400 °F in moderate to low LEL conditions
  • Internal combustion engine (IC Engine) – destroys vapors at the 80-90% range, and have a max intake flow of 25 CFM.
  • Scrubber Units – used for odor control only.  Scrubbers have a limited capacity for absorption; project management must account for safe disposal of the scrubbing media
  • Chemical Degassing methods – generally these proprietary chemical scrubbers are surfactants and do not degas a tank.
  • Refrigeration and Condensing – the theory is to condense the vapors back into liquid waste product.  Practically speaking, there are major concerns with trapping vapors, unsafe vapor leaks, and waste disposal.

A company permitted with the APCD/AQMD and completes Annual Source Testing.

Liquid scrubbers are sometimes deployed to “degas” tanks.  These systems are extremely ill suited for “degassing” most tanks, as they can only absorb a finite amount of Volatile Organic Compounds (VOCs).  There is no surefire way to know whether the chemical will work on all the constituents and for how long.  A typical crude tank will generate up to 100,000 lbs of vapor.  That means you will need 1,000,000 lbs of scrubber media, assuming you have a 1:10 absorption curve.  Once this media is spent, consider where the facility will dispose of it and whether or not the media itself has become hazardous.

Additionally, activated carbon is a technique that is used occasionally. The handling of activated carbon is a nuisance. Carbon is delivered in large boxes and has to be transferred to the carbon/plenum container. The cost of carbon is between $5 to $10 per pound considering disposal, handling, containers, etc. It may take anywhere from 8 to 12 pounds of carbon to control 1 pound of VOC. This means that the carbon cost alone may be $100,000 or more for one tank. It is not practical for degassing tanks and there is a serious risk of bed fires during or after the carbon has been used.

Tank degassing is the removal of vapors and displacement with nitrogen or fresh air usually done for API 653 Internal Tank Inspections. The elimination & capture of harmful emissions is achieved by using a proven solution, an Envent Vapor Destruction Unit (VDU), in place of a Fan or Horn Blower.

  • Envent’s specialist tank degassing
  • Improves safety
  • Eliminates personnel exposure
  • Supports verifiable Emissions Banking
  • Saves money
  • Cuts tank repair costs
  • Reduces lost opportunity costs
Envent Corporation | Understanding Your Options

After 20+ years of experience as a specialist degassing contractor, Envent is confident that the best method is the device and technique that performs the job the fastest while being safe and environmentally compliant.  These are key conditions.  The degassing of a tank can be a very hazardous event.  During the degassing process, the tank will inevitably go through the explosive range.  Getting your tank through this as quickly as possible is the first key to safe degassing.  However, doing it safely depends on the equipment, the safety devices employed, the compliance assurance program, and the operators’ experience.

After more than 20 years, Envent Corporation has determined that a system with high flow and specially designed burner is the best option for terminals and refineries.  The EMTOS unit flow rates range from 1,000 to 6,000 CFM – More than twice the flow of similar systems.

Envent’s EMTOS meets all criteria for performing these operations. Call our on-call engineers 24/7 to build a quote.

Rob Ferry illustrates how much VOC’s are created during this process with his API 2568.  Typically, 5000 lbs. – 10,000 lbs. of vapor are released and need to be degassed by a specialist contractor.

The EMTOS is the most effective means of degassing tanks. These large mobile degassing units are the fastest way to destruct your tank vapors. The combustion of vapors is

  • 99.99% effective
  • documented by third party source tests
  • continually verified and documented during operation with continuous temperature chart recorders, Flame Ionization Detectors, Photo Ionization Detectors and Flow Meters

The EMTOS is the only system capable of degassing tanks, pipelines and vessels in a matter of hours rather than days or weeks. Our systems can handle up to 6,000 CFM of vapor and can degas your tanks in hours with verifiable tank vapor space readings.

  • A 150 foot diameter tank will degas to 10% LEL in 6-8 hours depending on sludge/scale/product.
  • A 250 foot diameter tank will be completed in 18-24 hours.

The EMTOS is a proprietary unit engineered, designed and built by Envent engineers to provide the safest and most cost-effective solution to tank degassing in the world. We have spent over a decade continuously improving the operation and safety of the EMTOS.

Envent and the EMTOS have a clear advantage over the alternatives:

  • Get the tank through the explosive range rapidly and safely
  • The only system HazOpped by all major oil companies
  • Vapors are removed and destroyed – saving secondary costs
  • Compliance data are proven by yearly 3rd party source testing
  • Cost effective – EMTOS’ costs are 1/10th per MMBTU vs ICE and mini combustors
  • In full compliance with the agency – certified reporting

As the name describes, these are devices that thermally combust vapors, and are also sometimes known as ‘flares’ (TCEQ). The units are used for tank degassing as long as they prove and verify they can meet the requirement for minimum temperature (1400 deg F) and minimum residence time of 0.5 seconds.   Often, the terminology is used to avoid the compliance with the minimum 1400 deg F temperature limit.

While there are a number of ways to degas tanks the most effective method remains combustion. As degassing procedures expand to new geographic areas, we use Envent’s 20+ years of degassing experience to help new clients make the best decision for their particular project and its scenario. Particularly in areas where tank degassing has not been used before, it’s important to draw on Envent’s expertise as expertise to examine the logistics and scope of the projects in order to provide the best solutions.

Envent Dock Safety Unit (EDSU)

The EDSU is a skid-mounted safety system that our team locates near the barge or ship to be loaded.  Generally, we make space on the wharf or dock that is adjacent to the vessel.  EDSU provides the safety interlocks, isolation devices, pressure/vacuum relief valves, detonation arrestors and an enrichment system to maintain the marine vessel vent stream in a safe and non-explosive range.

EMECS interlocks with the EDSU to form a powerful, fully certified and 100% compliant Marine Vapor Control System.

Envent Mobile Emission Control System

The Envent Mobile Emission Control System (EMECS) is a rapid response system for ship and barge vapor controls.  EMECS has a 42MMBTU horizontal combustion unit with a fully enclosed thermal oxidizer firebox and dual horizontally-fired waste gas burners with a fixed pilot and flame safeguard system.  Due to its ‘Thermal Oxidizer’ status – consistent operation at temperatures greater than 1400 °F – the EMECS unit is required to be located a minimum of 30 meters from the closest operating marine berth.   It is capable of handing ship or barge loading fill rates up to 10,000 BBLs. per hour.

EMECS complies with all United States Coast Guard regulations includes safety equipment including fire-safe valves, detonation arrestors, and supplemental instrumentation that can instantly identify upset conditions.

Envent’s expertise with mobile wastewater treatment extends beyond industrial facilities to include a wide range of other wastewater sources. We have provided treatment solutions for wastewater generated by landfill leachate, refinery wastewater, sour water, storm water, groundwater and construction site dewatering.

Envent operates the nation’s largest fleet of transportable water treatment units, and our teams are available 24/7 to respond to emergencies anywhere in the country.  Call us when you need efficient and safety-oriented results at  888-997-9465 or email

Many factors contribute to determine which units should be utilized in any given degassing challenge, one of the most common ones is the presence of H2S.

Envent’s expertise with a multitude of challenges throughout the years means we will be able to accommodate your degassing needs and propose a viable solution.

Our teams are available 24/7 to respond to emergencies anywhere in the country.  Call us when you need efficient and safety-oriented results at  888-997-9465 or email

Envent Corporation | Why Choose Envent

When you want a specialist instead of a ‘jack-of-all-trades’ contractor, you start out needing some advice, so we designed this section for our customers and potential customers to get exactly that.  We make this information available to clients and potential clients so you can ensure that upcoming projects that require degassing operations meet the safety, quality, and efficiency that the #1 industry leader can provide.

Read our FAQs regarding technical analysis on degassing technologies, vapor control equipment, scrubbers, odor control systems, as well as safety information, HAZOP data, and source testing summaries. We also include details on Envent’s operating permits and authorizations as well as agency interpretations on FAQs regarding when permits are needed, when it’s acceptable to operate below 1400 °F, and the process as temperature drops.

As degassing becomes more important, degassing specialists are the ones that provide you with a solid reporting program with accurate and detailed reports that show full compliance. Envent ensures that this is what our clients receive, however, vacuum truck or tank cleaning companies may not.  Envent provides a Comprehensive Degassing Log with:

  • PID/FID calibration records
  • Continuous Temperature Monitoring
  • Verified Flow Measuring System
  • Required Source Testing Reports
  • Residence Time Certification
  • Correct Stack Monitoring

Two words: Safety and cost

There are a number of personal and environmental hazards that can occur when waste products go off-site in order to be processed.  By coming on-site, Envent has eliminated many of the risks related to these factors (and their associated costs) out of the equation.  By using a contractor with dedicated operators and equipment returns faster, safer, more cost effective solution for clients.

Envent’s 20+ years as a specialty contractor have allowed us to analyze and devise the right equipment set up for marine applications. In theory, marine degassing is similar to tanks on land that is introducing a new liquid displaces previously existing vapors from the tank, as well as creating vapors generated by the current loading – this is a hazardous situation. Given the additional hazards of a marine vapor destruction scenario, safety and compliance dictate a 2-part operation. Envent’s engineering team has created the perfect complement of equipment to get the job done right: EDSU maintains the marine vessel vent stream, and EMECS rapidly destructs vapors with > 99% efficiency.  Both systems work together to minimize the risk of explosion.

Tank degassing is the removal of vapors and displacement with nitrogen or fresh air usually done for API 653 Internal Tank Inspections. The elimination & capture of harmful emissions is achieved by using a proven solution, an Envent Vapor Destruction Unit (VDU), in place of a Fan or Horn Blower.

  • Envent’s specialist tank degassing
  • Improves safety
  • Eliminates personnel exposure
  • Supports verifiable Emissions Banking
  • Saves money
  • Cuts tank repair costs
  • Reduces lost opportunity costs

Environmental – Degassing using Envent reduces greenhouse gas emissions and your carbon footprint. A 100 ft. diameter gasoline tank will release 150,000 lbs. – 250,000 lbs.* of Volatile Organic Compound (VOC) emissions uncontrolled.

*Calculations based on the American Petroleum Institute (API) Publication 2568, authored by Rob Ferry.

Personnel Exposure – Eliminate Exposure to Employees, Contractors and Neighbors. Gasoline vapors are heavier than air and when they are blown out of the tank using a fan blower, personnel in the area are exposed. The Permissible Exposure Limit (PEL) for benzene is set as “8-hour time weighted average exposure of 1 ppm or the short-term exposure limit of 5 ppm for 15 minutes”, as per OSHA regulations.

Safety – Blowing gasoline or other volatile vapors into an uncontrolled area has obvious safety issues. A January 2009 tank degassing fire ignited by smokers on the designated smoking pad resulted in 4 serious injuries.

Call (888) 997-9465 and ask for the engineer nearest your area or email us at

That’s easy – permits are a part of Envent’s job.  We often assist clients by obtaining permits on their behalf.  Part of the assurance that comes from hiring a specialty company is knowing that we maintain excellent working relationships with key regulatory authorities, and our deep expertise in environmental permitting benefits our clients.  We hold many environmental permits including:

  • AQMD/APCD permits.
  • State permits in New Jersey, Louisiana, Illinois, and other locals.
  • POTW permits.
  • NPDES permits.
  • Special discharge-to-land  authorizations.
  • EPA/USCG authorizations/certifications.
  • Transportable Treatment Unit (TTU) Permits.

as well, which means that we can rapidly deploy projects for our customers.  We maintain a portfolio of over 175 current environmental permits; likely Envent already holds the authorizations your project needs. If not, our engineers will guide your team through complex agency requirements to attain what your project needs.  Regulatory agencies respect the quality of Envent’s engineering and solutions – we’ve found that there is no substitute for experience and good reputation when it comes to professional networking and we’re happy to help you.

Envent’s specialty services encompass soil remediation and soil vapor extraction as well. We are routinely contracted by engineers, petrochemical and energy plants to install systems to handle the remediation of different sizes of facilities. We’re happy to work with your engineers and technicians to design and to execute the field installation of necessary equipment like air sparging units, and vacuum extraction units.

Envent is the nation’s leader for pipeline hydrostatic testing, and remediation of water used for this testing in the petrochemical industries. We have the nation’s largest fleet of mobile pipeline and tank hydro-testing equipment in North America and our treatment systems are designed to keep your project 100% in compliance with local, state, and federal regulations. We meet all discharge permit requirements for general water quality, volume and flow rate.