Vapour Recovery Units (VRU): How They Work, Types and Uses
BM PROCESS · FAQ
Vapour Recovery Units (VRU): How They Work, Types and Uses
By the BM Process Management engineering team · Reviewed by our vapour recovery and emission control engineers · Last reviewed: September 2026
A vapour recovery unit (VRU) is a system that captures hydrocarbon vapours that would otherwise be vented during storage, loading or processing, and returns them to a usable liquid or fuel-gas stream. Instead of losing product and emitting VOCs, a VRU recovers the vapour, cutting both emissions and losses at the same time.
This page explains how a vapour recovery unit works, its main components such as the compressor and vapour recovery tower, the recovery methods and VRU packages available, and where VRUs are used in oil and gas, at tank terminals and on truck and marine loading. BM Process designs and integrates vapour recovery units end to end.
Vapour Recovery Units (VRU): Frequently Asked Questions
VRU basics and how it works
What is a vapour recovery unit (VRU) and what does VRU stand for?
A vapour recovery unit, or VRU, is a system that captures hydrocarbon vapours that would otherwise be vented during storage, loading or processing, and returns them to a usable liquid or fuel-gas stream. VRU stands for vapour recovery unit (also written vapor recovery unit). Instead of losing product and emitting VOCs, a VRU recovers the vapour, cutting both emissions and losses. It is a core building block of any modern vapour emission control system.
How does a vapour recovery unit work?
Vapours displaced from a tank or loading arm are collected and drawn into the unit, where they are typically compressed, then condensed or absorbed so the hydrocarbons return to liquid form while clean gas is released or reused. Common methods are compression and condensation, carbon or lean-oil absorption, and membrane separation. The choice depends on vapour composition, flow rate and recovery target.
What is a vapour recovery unit compressor?
The compressor is the heart of many VRUs. It raises the pressure of the collected vapour so it can be condensed back to liquid or pushed into a fuel-gas or absorption system. Compressor selection, sealing and control are critical to reliable recovery and safe operation, which is why VRU packages are engineered around the vapour’s flow, pressure and composition rather than bought off the shelf.
What is a vapour recovery tower and how does it differ from a VRU?
A vapour recovery tower is a vessel used mainly at oil production sites to capture the low-pressure flash gas that comes off crude before it reaches the storage tanks, stabilising the liquid and routing the recovered vapour on for compression or further recovery. It often works together with a VRU: the tower captures and separates the vapour, and the recovery unit compresses and processes it.
VRU types, methods and packages
What are the main types and methods of vapour recovery system?
The main recovery methods are compression and condensation, in which the vapour is compressed and cooled back to liquid; absorption, in which the vapour is absorbed into a lean oil or passed over activated carbon and then stripped; and membrane separation, which uses selective membranes to concentrate and recover the hydrocarbons. Many real systems combine methods in stages, and the right choice depends on vapour composition, flow and recovery target.
How do you design and size a vapour recovery unit?
Sizing starts with the peak and average vapour flow, the vapour composition and the target recovery or emission limit. From there the recovery method, compressor duty, condensation or absorption stages and controls are engineered together. A well-designed VRU balances recovery efficiency, energy use and reliability rather than simply maximising one of them. BM Process handles this design and integration end to end.
What is a VRU package and what does it include?
A VRU package is a pre-engineered, skid-mounted unit that bundles the compressor, separation or condensation equipment, instrumentation, safety systems and controls into a single deliverable. Packaging shortens installation time and simplifies integration with the wider vapour control system, while still being tailored to the site’s vapour stream.
Can a VRU be used for natural gas as well as liquids?
Yes. VRUs are widely used to recover natural gas and light hydrocarbons that would otherwise be flared or vented, for example casinghead or tank flash gas at production sites. Recovering this gas returns saleable product and cuts methane emissions. The unit is configured for the specific gas composition and pressure.
Who manufactures VRUs, and how big is the vapour recovery units market?
VRUs are supplied by specialist packagers and engineering firms, and the vapour recovery units and services market has grown as emission limits have tightened worldwide, including in oil and gas. Rather than a fixed product, each unit is engineered to the site’s vapour stream, which is why the design and integration matter more than the badge.
Uses in oil, gas, storage and loading
Where are vapour recovery units used in oil and gas?
In oil and gas, VRUs are used on crude and product storage tanks, at truck and rail loading racks, on marine loading jetties and around process equipment where light hydrocarbons flash off. They capture vapours that would otherwise be flared or vented, recovering saleable product and keeping VOC and methane emissions within permit limits.
What is a tank vapour recovery system for storage tanks?
A tank vapour recovery system captures the vapours that storage tanks give off as they are filled or as temperature and pressure change through the day. Instead of venting through the tank’s pressure or vacuum vents, the vapour is collected and sent to a recovery unit. This is a common way to cut both product loss and VOC emissions from tank farms while keeping the tanks within their permit.
What is a vapour recovery system for truck loading?
During truck loading, liquid entering the tanker displaces vapour that must go somewhere. A truck-loading vapour recovery system collects that displaced vapour through the loading arm and routes it to a VRU or vapour destruction unit instead of the atmosphere. It is a standard requirement at compliant loading terminals and protects both air quality and operators.
What is marine vapour recovery?
Marine vapour recovery captures the large volumes of vapour displaced when a vessel is loaded at a jetty. Because marine loading rates are high, these systems are sized for large, variable flows and must meet strict safety and interlocking standards. They combine vapour collection, safety equipment and either recovery or destruction of the collected vapour.
What is a gasoline or fuel vapour recovery system?
A gasoline or fuel vapour recovery system captures the petrol vapours displaced during storage and loading, which are both a valuable product and a significant VOC source. At terminals and depots the displaced vapour is collected and recovered rather than released. The same principle applies from large loading racks down to fuel dispensing, though industrial systems are engineered for far higher flows.
Where is a VOC recovery unit used and what about drum filling?
A VOC recovery unit captures volatile organic compounds from storage, loading, drum filling and process vents so the solvent or hydrocarbon can be reused and emissions cut. It is used across oil and gas, chemicals and any operation that handles volatile liquids. The recovery method is matched to the specific VOCs present.
Recovery vs destruction, control and maintenance
What is the difference between a vapour recovery unit and a vapour destruction unit?
A vapour recovery unit turns captured vapour back into usable product, so it pays back through recovered material. A vapour destruction unit, such as a thermal or catalytic oxidiser, burns the vapour to a harmless state without recovering it. The right choice depends on vapour value, flow rate and site constraints; often the two are combined, with recovery as the primary route and destruction as backup.
What is a vapour control system and how does refinery vapour control fit in?
A vapour control system is the wider set of equipment that manages hydrocarbon vapours across a site, combining vapour collection, recovery units, destruction units where needed, safety devices and controls. A VRU is one component within it, working alongside the wider emission control train. At refineries and terminals, designing the control system as a whole, rather than adding equipment piece by piece, is what keeps a site compliant and efficient.
What does VRU repair and maintenance involve?
VRU maintenance focuses on the parts that do the work under pressure and cyclic duty: the compressor and its seals, valves, instrumentation, and the condensation or absorption media. Reliable recovery depends on keeping these in good order and on the controls being correctly tuned. Because a VRU protects both compliance and product, planned maintenance and prompt repair of any fault are important to avoid unplanned venting.
Does BM Process design and integrate vapour recovery units?
Yes. BM Process designs and integrates vapour recovery units for storage, loading and process applications, handling the sizing, recovery-method selection, packaging and integration with the wider vapour and emission control system. Because we combine process engineering with emission control, the VRU is designed as part of the plant it serves. Outline your requirements at https://bmprocess.nl/.
About BM Process Management
Written and reviewed by the BM Process Management engineering team. BM Process Management is an industrial process and emission control engineering consultancy based in the Netherlands, providing independent engineering, abatement and emission monitoring services for industrial clients across Europe. The answers on this page reflect field experience in designing and integrating vapour recovery units.
