Summary

A positive pressure container protects personnel and equipment by maintaining the internal pressure above the surrounding atmosphere, so airflow moves outward through controlled leakage paths rather than allowing external gas, vapour or dust to enter. It is commonly used for offshore laboratories, mud logging cabins, control rooms and MCC or switchgear shelters.

Pressure alone is not a complete specification. A reliable solution must integrate the enclosure, clean-air source, purge and pressurization system, HVAC, gas detection, alarms, shutdown logic, fire protection, electrical equipment, cable and pipe penetrations, doors and host-facility interfaces. The correct design depends on the hazardous-area classification, internal equipment, process releases, installation location and required certification.

What Is a Positive Pressure Container?

A positive pressure container is an enclosed module supplied with clean air at a rate that keeps its internal pressure higher than the external atmosphere. When the enclosure is intact, the pressure differential establishes outward airflow at doors, seals and other defined leakage paths. This helps prevent a hazardous external atmosphere from entering the protected space.

The system is useful when equipment that is suitable for operation in a clean or safe internal environment must be installed near flammable gas, vapour or dust hazards. Typical applications include:

• MCC, switchgear, MCP, VFD and VSD shelters;
• offshore laboratories and mud logging cabins;
• control, instrumentation and monitoring rooms;
• workshops and equipment cabins; and
• other occupied or equipment modules located in a project-defined hazardous area.

TLS manufactures standard and customized pressurized modules for offshore and onshore projects. The protective concept, equipment selection and certification scope must nevertheless be established for each installation.

How Does the Protection System Work?

The operating sequence normally begins with a purge using air from a verified safe source. The purge replaces the initial internal atmosphere before equipment that depends on pressurization is energized. The system then maintains the required pressure and monitors whether the protected condition remains valid.

A project-specific control philosophy may include:

1. confirmation that doors and access points are closed;
2. verification that the air source and airflow are available;
3. a timed or volume-based purge before energization;
4. continuous pressure monitoring during operation;
5. external gas detection at the fresh-air intake and other defined locations;
6. alarms if pressure, airflow or gas conditions move outside permitted limits; and
7. automatic isolation, ventilation response or power shutdown according to the risk assessment.

The exact sequence cannot be selected from container size alone. Required purge volume, minimum pressure, leakage allowance, alarm delays and shutdown actions must be defined against the applicable protection concept and project requirements. The IEC 60079 series provides the international framework for equipment and installations in explosive atmospheres; the precise parts and edition must be stated in the project specification.

Why Is Pressurization Not Enough by Itself?

Positive pressure primarily addresses an external hazard: it helps prevent a hazardous atmosphere outside the module from reaching equipment and personnel inside. It does not remove a flammable or toxic substance released within the module.

This distinction is especially important in laboratories and mud logging cabins. Samples, chemicals, process lines or equipment can create an internal release even when the room is successfully pressurized. Depending on the hazard assessment, the design may therefore require:

• an explosion-proof fume hood or local extraction system;
• dedicated exhaust connections for safety cabinets or process equipment;
• internal detection for gases such as methane or hydrogen sulphide;
• Ex-rated electrical equipment where ignition risk remains;
• emergency ventilation and shutdown functions;
• segregation of hazardous work from clean equipment areas; and
• fire detection, emergency lighting, an emergency stop and safe escape provisions.

The clean-air pressurization system and the process exhaust system must be balanced as one ventilation design. Excessive extraction can collapse positive pressure, while insufficient extraction can allow an internal contaminant to accumulate. Airflow calculations and control logic must cover normal operation, door opening, equipment extraction and emergency conditions.

What Can a TLS Positive Pressure Module Include?

TLS brochure configurations show that the final module can combine structural, safety and operational systems. Depending on the agreed scope, a positive pressure container may include:

• a DNV 2.7-1/EN 12079 offshore container structure or an ISO/CSC transport configuration;
• A-0 or A-60 fire-rated boundaries where required;
• an airlock or controlled access arrangement;
• a combined pressurization, fire and gas control panel;
• pressure switches, flow monitoring, solenoid valves and loss-of-pressure alarms;
• gas and smoke detectors;
• fail-safe fire dampers;
• HVAC designed for the occupancy and equipment heat load;
• Ex-approved external or internal electrical components as required;
• emergency lighting, fire extinguishers, emergency stops and an escape hatch;
• MCT frames or other certified cable and pipe transit systems; and
• fast-plug electrical and utility interfaces.

These are available features, not a universal standard package. Each item must be confirmed in the quotation, drawings and certification scope.

How Do Laboratory and MCC Shelter Requirements Differ?

Positive pressure laboratory or mud logging cabin

A laboratory is an occupied process space. Its design must address personnel safety, chemical compatibility, sample handling, water and drainage, furniture, work surfaces, fume extraction, lighting, communications and emergency response in addition to pressurization.

TLS brochure examples include laboratory configurations with resistant workbenches, sinks, storage, fume hoods, eye wash equipment, fire and gas detection, HVAC and connections to host utilities. A reference mud logging cabin is shown as a 20ft module with DNV 2.7-1/EN 12079 structural rating, A-60 protection and Zone 1/Zone 2-related systems. These details describe particular configurations and should not be assumed for every laboratory.

MCC or switchgear pressurized shelter

An MCC shelter is primarily an engineered environment for electrical assets and maintenance access. The internal layout is driven by the customer's MCC, switchgear, PLC, VFD/VSD and auxiliary equipment. Critical inputs include heat dissipation, arc-flash boundaries, cable entry, floor loading, working clearances, replacement routes and maintainability.

TLS offers nominal 15ft, 20ft and 40ft shelter formats as well as custom dimensions. Positive pressure, HVAC and fire-and-gas functions protect the internal operating environment, while the customer and equipment supplier must still define panel ratings, electrical protection, arc-flash controls and installation requirements. The shelter supports the electrical equipment; it does not replace its own safety design.

What Do DNV 2.7-1, IEC 60079 and A-60 Cover?

These requirements address different risks and should not be treated as interchangeable certificates.

DNV 2.7-1 and EN 12079

DNV-ST-E271, commonly called DNV 2.7-1, addresses offshore container design, manufacture, testing, marking, inspection and lifting sets. EN 12079 is also widely specified for offshore containers. These requirements establish offshore structural and handling capability; they do not alone approve the pressurization, fire protection or hazardous-area concept.

IEC 60079

The IEC 60079 series addresses equipment and installations in explosive atmospheres. The applicable part, protection concept, equipment protection level, gas or dust group, temperature class, zone and certification basis must be defined. A general statement such as “Zone 1/Zone 2 suitable” is not sufficient without the exact design and approval scope.

A-60 fire protection

A-60 addresses fire integrity and insulation performance of the specified boundary assembly under prescribed test conditions. Walls, roof, floor, doors, dampers, penetrations and joints must preserve the required boundary. A-60 does not certify hazardous-area protection or offshore lifting.

What Should Buyers Define Before Requesting a Quotation?

Provide the following information at the enquiry stage:

1. Application: laboratory, mud logging, control room, MCC, switchgear or another function.
2. Installation: offshore platform, vessel, FPSO, onshore plant or other host facility, including the exact proposed location.
3. Hazardous-area basis: zone, gas or dust group, temperature class, external hazards and applicable client standards.
4. Internal release sources: samples, chemicals, process lines, batteries or equipment that can release gas, vapour, heat or dust.
5. Certification: DNV 2.7-1/EN 12079, CSC, IECEx, ATEX, class approval, A-0/A-60 or other stated requirements.
6. Clean-air source: location, quality, duct route, available pressure and the method used to confirm that the intake remains safe.
7. Pressurization logic: purge sequence, pressure set points, alarm levels, door status, gas detection, shutdown and recovery philosophy.
8. HVAC and extraction: ambient conditions, occupancy, equipment heat load, required internal conditions, fume hood or process exhaust and redundancy.
9. Electrical interfaces: voltage, frequency, connected loads, fault level, earthing, cable entries, socket standard and Ex requirements.
10. Equipment data: dimensions, weights, heat loads, access clearances, maintenance routes and cable schedules for customer-supplied equipment.
11. Fire and safety systems: fire and smoke detection, suppression interfaces, emergency stop, emergency lighting, escape and host alarms.
12. Transport and installation: dimensions, weight limits, lifting set, deck loading, tie-down, stacking and access restrictions.
13. Testing and documents: calculations, drawings, certificates, inspection plan, FAT scenarios and commissioning responsibilities.

Frequently Asked Questions

Does positive pressure make all internal equipment explosion-proof?

No. Pressurization can form part of a hazardous-area protection strategy, but the complete system must be engineered, controlled and certified for the intended application. Equipment exposed during loss of pressure, purge, maintenance or an internal release may require additional protection.

Can a positive pressure laboratory contain hazardous chemicals generated inside?

Not by pressure alone. Positive pressure drives air outward and is mainly used to exclude external contamination. Internal hazardous releases normally require local exhaust, treatment, detection, suitable electrical equipment and emergency logic based on the process risk assessment.

Is every TLS pressurized container DNV 2.7-1 and A-60 certified?

No. TLS can supply configurations with these requirements, but certification and fire rating must be specified and confirmed for the exact project and module.

Can an MCC shelter use non-Ex switchgear?

Potentially, if the complete pressurized-room protection concept permits it and all operating, purge, alarm and failure conditions are addressed. The decision must be made by the responsible hazardous-area engineering and certification parties, not assumed from the enclosure alone.

What is the most important early design decision?

Define whether the main hazard is outside the module, inside the module or both. That decision determines whether positive pressure is appropriate and what extraction, detection, equipment protection and interlocks are also required.

Request a Project-Specific Positive Pressure Container Review

TLS Offshore Containers supplies pressurized laboratories, mud logging cabins, MCC and switchgear shelters, control modules and other customized containerized solutions. Send TLS your application, hazardous-area classification, internal equipment, release sources, required certification, ambient conditions, electrical supply, HVAC loads, utility interfaces and target delivery schedule.

Contact TLS Offshore Containers to request a preliminary technical review or quotation.

Further reading:

• TLS pressurized container solutions for hazardous areas

• TLS MCC pressurized shelter overview

• TLS A-60 offshore DNV 2.7-1 pressurized container brochure

Summary

A negative pressure container maintains a lower internal pressure than the surrounding environment so that air flows inward when a door opens, or a small leakage path is present. Its purpose is containment: reducing the uncontrolled escape of hazardous vapours, gases, dust or other airborne contaminants generated inside the module.

Negative pressure is not a complete safety solution by itself. The exhausted air must be captured, filtered, treated or discharged to a verified safe location according to the hazard. The module also requires suitable air inlets, ventilation rates, pressure monitoring, alarms, electrical equipment, process extraction, emergency logic and host-facility interfaces. Selection should begin with the substance and release scenario, not with a target pressure copied from another project.

What Is a Negative Pressure Container?

A negative pressure container is a controlled workspace in which mechanical exhaust removes more air than is supplied. The resulting pressure differential causes replacement air to enter through designated inlets and access points, establishing airflow from the surrounding area into the contained space.

This arrangement is useful when the primary risk originates inside the module and must be prevented from spreading to adjacent work areas. Typical applications include:

• chemical or sample-handling laboratories;
• mud laboratories and analytical cabins;
• dust sampling or material handling modules;
• industrial processes that release vapour, odour or airborne particles; and
• other project-specific containment workspaces.

The term “negative pressure” describes airflow direction. It does not, by itself, confirm biological containment level, hazardous-area suitability, filtration performance or safe exhaust discharge.

How Does a Negative Pressure System Work?

A complete system controls the path of air from entry to discharge:

1. Replacement air enters through defined inlets or a controlled supply system;
2. airflow moves from cleaner areas toward the work or release zone;
3. local extraction captures contaminants close to their source where practicable;
4. the general exhaust maintains the required room pressure and ventilation rate;
5. filters, scrubbers or other treatment devices are selected for the specific contaminant;
6. the discharge point is positioned and assessed to prevent exposure or re-entry; and
7. pressure, airflow and gas conditions are monitored, with alarms and emergency actions if control is lost.

Room pressure is only one performance indicator. A pressure reading can remain negative even if a fume hood is not capturing properly, a filter is saturated or the exhaust is discharged to an unsafe location. Commissioning and periodic testing must therefore verify airflow direction, capture performance, alarm functions and the complete exhaust path.

When Should a Project Choose Negative Pressure?

Negative pressure is generally appropriate when the surrounding environment can safely provide replacement air and the significant airborne hazard is produced inside the module. The purpose is to keep that internal hazard from escaping into nearby occupied areas.

It may not be appropriate as a standalone strategy when the external atmosphere itself can contain flammable or toxic gas. In that situation, inward airflow can draw the external hazard into the module. A project with both external and internal hazards needs a more detailed concept, which may use zoning within the module, airlocks, source capture, treated supply air, specialized equipment or another engineered arrangement.

The correct pressure strategy must be determined through the project risk assessment. Positive pressure excludes an external hazard; negative pressure contains an internal hazard. Neither principle should be selected merely because a similar module used it.

What Must Happen to the Exhausted Air?

Air removed from a negative pressure container cannot automatically be released to the surrounding environment. The required treatment depends on the substance, concentration, release rate and applicable environmental and occupational requirements.

The design may require:

• particulate filtration selected for the particle size and loading;
• activated carbon or another adsorbent for compatible vapours;
• wet or dry scrubbing for specified chemicals;
• dedicated ducting for a fume hood or process enclosure;
• explosion-protected fans and duct components where a flammable atmosphere can occur;
• safe discharge height and location based on dispersion and air-intake positions;
• differential-pressure monitoring across filters;
• safe filter change-out, isolation and disposal procedures; and
• sampling points or emissions monitoring where required.

HEPA filtration is designed for particles; it is not a universal treatment for gases or vapours. Likewise, activated carbon is contaminant-specific and has a finite capacity. The treatment train must be selected by qualified process, industrial hygiene and environmental specialists using actual substance data.

What Safety Systems May Be Required?

TLS negative pressure configurations can be developed around the process and project requirements. Depending on the agreed design, a module may include:

• a weather-resistant offshore or onshore container structure;
• DNV 2.7-1/EN 12079 certification or CSC plating where specified;
• A-0 or A-60 fire-rated boundaries;
• duty and emergency exhaust fans;
• controlled make-up air and pressure monitoring;
• gas, fire and smoke detection;
• local extraction or an explosion-proof fume hood;
• acid- and alkali-resistant, anti-static work surfaces;
• Ex-rated lights, switches, sockets, cabling and fans where required;
• HVAC, water, drainage, compressed air, data and communication interfaces;
• emergency lighting, emergency stop, eye wash or safety shower; and
• alarms, shutdowns and connections to the host control system.

These are possible project features, not an automatic package. A negative pressure set point, fan arrangement or shutdown sequence used on one TLS project should not be applied to another without verifying the hazard and airflow calculations.

How Should Normal and Emergency Modes Be Defined?

Some TLS negative pressure laboratory projects use separate normal and emergency exhaust modes. A smaller fan can maintain routine containment, while a larger Ex-rated fan starts following specified gas detection. The control system can then alarm or isolate power if the gas condition does not recover.

This is a useful reference architecture, but the published pressure figures and alarm delays from a previous configuration are not universal design values. The project must define:

• the substances to be detected and their sensor locations;
• normal and credible maximum release rates;
• required air changes and source-capture velocity;
• normal, low-pressure and emergency alarm thresholds;
• fan duty, redundancy and power availability;
• safe state following fan failure, high gas, fire or power loss;
• which electrical loads remain energized during an emergency;
• conditions for automatic or manual restart; and
• how exhaust treatment performs at both normal and emergency flow.

Emergency exhaust can increase containment but can also overload filters, disturb fume-hood balance or create excessive door forces. All modes must be calculated, tested during FAT and verified after installation.

What Do DNV 2.7-1, A-60 and Hazardous-Area Standards Cover?

Different requirements control different parts of the module.

DNV 2.7-1 and EN 12079

DNV-ST-E271, commonly called DNV 2.7-1, addresses offshore container structure, manufacturing, testing, marking, inspection and lifting sets. EN 12079 is also commonly specified. These standards do not determine the correct containment pressure, filter efficiency or exhaust treatment.

A-60 fire protection

A-60 relates to the integrity and insulation performance of a specified fire boundary assembly. Doors, dampers, ducts, penetrations and joints must maintain the required boundary. Fire rating does not establish biological containment or gas-removal performance.

IECEx, ATEX and IEC 60079

If a flammable atmosphere can exist inside the module or exhaust system, the area classification and equipment protection requirements must be defined. The IEC 60079 framework addresses equipment and installations in explosive atmospheres. IECEx or ATEX conformity may be requested depending on the jurisdiction and project, but the exact zone, gas or dust group, temperature class, protection concept and certificate scope must be stated.

How Is a Negative Pressure Laboratory Different from a Biosafety Laboratory?

Negative room pressure is one containment feature used in some biological facilities, but it does not create a biosafety laboratory by itself. Biosafety classification also depends on facility design, work practices, primary containment equipment, decontamination, waste handling, personnel procedures, filtration and validation.

Buyers should not describe a container as a particular biosafety level unless the complete facility and operating program have been designed and assessed against the applicable national or international requirements. A project handling infectious material requires specialist biosafety input beyond a standard industrial laboratory specification.

What Should Buyers Define Before Requesting a Quotation?

A useful enquiry should include:

1. Process and substances: names, safety data, physical form, toxicity, flammability, particle size and occupational or environmental limits.
2. Release scenarios: routine emission, maximum credible release, duration, temperature and location within the module.
3. Containment objective: personnel protection, environmental protection, cross-contamination control or a combination.
4. External environment: whether hazardous gas, dust or contamination can be present outside the module.
5. Installation: offshore platform, vessel, drilling site, mine, plant or another host facility, with the exact location.
6. Required approvals: DNV 2.7-1/EN 12079, CSC, A-0/A-60, IECEx, ATEX, class, client or regulatory requirements.
7. Ventilation criteria: pressure range, air changes, source-capture requirements, diversity, fan redundancy and noise limits.
8. Exhaust treatment: filters, scrubbers, monitoring, safe change-out, waste route and discharge location.
9. Detection and control: gases, detector locations, alarm levels, fan sequencing, power isolation, host alarms and recovery logic.
10. Electrical classification: internal and external zone, gas or dust group, temperature class, voltage, frequency, load and earthing.
11. Laboratory layout: fume hoods, benches, cabinets, sinks, eye wash, safety shower, sample routes and clean/dirty workflow.
12. Utilities: clean make-up air, power, water, drainage, compressed air, network and communications.
13. Transport and installation: module size, weight, lifting, deck loading, tie-down, stacking and maintenance access.
14. Testing and validation: airflow visualization, pressure tests, hood testing, alarm simulation, filter integrity, FAT, commissioning and periodic recertification.

Frequently Asked Questions

Does negative pressure remove hazardous gases?

No. It controls airflow direction and helps contain airborne hazards. The exhaust system must still capture and safely treat or discharge the contaminant.

Is a stronger negative pressure always safer?

No. Excessive pressure can make doors difficult to operate, disrupt local extraction, increase leakage through unintended paths and overload the exhaust system. The set point must be justified by the containment and ventilation design.

Can a negative pressure container be installed in Zone 1 or Zone 2?

Only with a project-specific design. Because negative pressure draws outside air inward, the external hazardous atmosphere and internal ignition sources must be carefully assessed. Suitable Ex equipment and a different airflow or zoning concept may be required.

Does a HEPA filter remove chemical vapours?

Generally, no. HEPA filters capture particles. Chemical gases and vapours require treatment selected for their properties, such as compatible adsorption or scrubbing systems.

Is every TLS negative pressure container DNV 2.7-1 and A-60 certified?

No. TLS can provide offshore and fire-rated configurations, but the exact certification, fire boundary and equipment scope must be specified and confirmed for the purchased module.

What is the most important first question?

Identify what must be contained, how much can be released and where the exhaust can be safely treated or discharged. Those answers determine the airflow, equipment, monitoring and approval strategy.

Request a Project-Specific Negative Pressure Container Review

TLS Offshore Containers supplies customized laboratory, mud lab and industrial containment modules for offshore and onshore applications. Send TLS the substances and process description, release scenarios, external area classification, containment objective, required certification, exhaust-treatment requirements, utilities and target delivery schedule.

Contact TLS Offshore Containers to request a preliminary technical review or quotation.

Further reading:

• TLS: when negatively pressurized containers are required

• Please download the Laboratory container brochure for reference.

Direct Answer

An offshore laboratory or workshop container should be designed around the **work process, equipment, hazards and installation environment**, rather than by selecting a standard container first. At a minimum, the project must define equipment dimensions and weight, personnel capacity, heat loads, chemicals or gases, ventilation method, hazardous-area classification and platform interfaces.

TLS provides customised offshore laboratories, workshops, crane-support containers, generator containers, ROV and control cabins, equipment and tool-storage containers, and maintenance cabins. Available systems include insulation, air conditioning, filtered extraction, electrical distribution, lighting, communications, and fire and gas detection. Depending on the project scope, relevant requirements may include DNV 2.7-1, NORSOK, ATEX/IECEx and SOLAS/IMO.

What Are the Main Design Priorities for Different Functional Containers?

Key conclusion: The external structures may be similar, but containers with different functions should not use identical ventilation, safety or acceptance criteria.

What Five Factors Should Be Confirmed During Design?

1. Work Process and Layout

Define how personnel, samples, tools and equipment will move through the module before positioning workbenches, storage, doors and emergency equipment. Sufficient operating and maintenance clearance must also be provided around each item of equipment.

2. Hazardous-Area Requirements

Modules installed in Zone 1 or Zone 2 may require positive pressurisation, hazardous-area-rated external equipment, gas detection and loss-of-pressure interlocks. The hazardous-area drawing and actual sources of release should determine whether these measures are required.

3. HVAC and Process Exhaust

HVAC primarily controls temperature and humidity, while process exhaust captures fumes, dust or chemical vapours. These systems have different purposes. Exhaust from a laboratory fume cupboard must also be assessed together with module make-up air and any positive-pressurisation system.

4. Structure and Weight

Equipment weight, centre of gravity, dynamic loads and mounting locations affect base-frame reinforcement, the module’s overall centre of gravity and its lifting attitude. The module weight report should be updated after heavy equipment has been finalised.

5. Platform Interfaces

Define the power supply, earthing, UPS, communications, fire and gas alarms, emergency shutdown and cable-entry locations. Factory-installed equipment reduces onsite work, but does not mean that all site interfaces are complete.

What Does Each Standard Address?

- DNV 2.7-1: Primarily addresses offshore-container structure, manufacture, testing and lifting. It does not verify laboratory ventilation performance.

- NORSOK: Refers to a family of standards. The applicable standard number, revision and clauses should be stated in the enquiry.

- ATEX/IECEx: Address equipment and conformity requirements for explosive atmospheres. They do not replace offshore structural certification.

- SOLAS/IMO: Applicability depends on the vessel, offshore facility and relevant authority. These requirements do not replace a project-specific process-safety design.

 What Information Does TLS Need for a Quotation?

- Module function, work process and number of personnel;

- Equipment dimensions, weight, heat load and maintenance clearance;

- Information about chemicals, gases, dust or fuel;

- Installation location, hazardous-area classification and environmental conditions;

- HVAC, process-exhaust or positive-pressurisation requirements;

- Power, communications, F&G and ESD interfaces;

- Applicable standards, third-party approval and FAT requirements;

- Quantity, delivery location and required schedule.

Frequently Asked Questions

1. Does every offshore laboratory require positive pressurisation?

No. The need for positive pressurisation depends on the external hazardous-area classification and internal sources of release. A module installed in a non-hazardous area without the relevant internal hazards may use a conventional ventilation arrangement.

2. Does a DNV 2.7-1 certificate allow the container to be used on any offshore platform?

No. The platform operator must still review the installation location, weight, lifting arrangement, fire protection, hazardous-area requirements and system interfaces.

3. Can a fume cupboard discharge directly outside the container?

Not without assessing the substance being discharged, the risk of exhaust-air re-entry, the hazardous-area classification and environmental requirements. The exhaust airflow may also affect internal positive pressure.

4. Why must equipment weight be confirmed early?

Equipment weight and centre of gravity directly affect structural reinforcement, maximum gross mass and lifting attitude. Replacing heavy equipment late in the project may require structural rework.

Conclusion

An offshore laboratory or workshop container is a functional system designed around a specific operation. Defining the equipment, hazards, ventilation and platform interfaces early reduces manufacturing changes and onsite commissioning risks.

TLS Offshore Containers / TLS Energy is a global supplier of standard and customised containerised solutions. 

Wherever you are in the world, TLS can help you. Please contact us.

Product brochures:

Offshore total pressurised container solutions

Offshore pressurised mud logging cabin brochure

MCC | Switchgear | VFD | VSD pressurised shelter