Short Answer
To specify a pressurised container, first define the hazardous-area classification and the intended function of the module. Then provide the external hazards, internal equipment, ventilation and pressurisation philosophy, fire-and-gas requirements, utilities, environmental conditions and certification basis.
“Zone 1/Zone 2 container” is not a complete technical specification. The zone, gas group, temperature class, equipment-protection requirements and operating philosophy must be established for the exact installation.
What Is a Pressurised Container?
A pressurised container is an enclosed module supplied with clean air so that its internal pressure is maintained above the surrounding atmosphere. This controlled outward airflow helps prevent a potentially hazardous external gas or vapour atmosphere from entering the protected space.
Typical uses include control rooms, MCC and switchgear shelters, VFD cabins, laboratories, mud logging cabins and instrumentation modules located near offshore or onshore process hazards.
The container structure, HVAC, fresh-air intake, pressure controls, alarms, shutdown logic, fire-and-gas system and cable penetrations must work as one engineered system.
What Is the Difference Between Zone 1 and Zone 2?
In gas hazardous-area classification, Zone 1 is an area in which an explosive gas atmosphere is likely to occur in normal operation. Zone 2 is an area in which it is not likely to occur in normal operation and, if it does occur, will exist only for a short period.
The classification is assigned by the project’s hazardous-area study. A container supplier should not guess the zone from a general description such as “near the process area.” The client should provide the hazardous-area drawing, relevant release information and applicable standards.
What Information Must Be Defined Before Design Starts?
1. Module function and internal equipment
State whether the module is a control room, electrical shelter, laboratory, workshop or another application. Include equipment dimensions, weights, heat dissipation, maintenance clearances and cable routes. The enclosure protects and supports the equipment; it does not eliminate the need to engineer the equipment itself.
2. Hazardous-area basis
Provide the zone, gas group, temperature class, equipment-protection level where applicable, hazardous-area drawings and client standards. Also identify external hazards such as flammable gas, hydrogen sulphide, dust, blast, salt exposure and extreme temperatures.
3. Pressurisation and purge philosophy
Define the safe-air source, intake location, duct routing, purge sequence, required operating pressure, door-opening conditions, alarm thresholds and response to loss of pressure. A typical system verifies air availability, purges before energising protected equipment, monitors pressure continuously and initiates alarms or defined shutdown actions when the protective condition is lost.
The exact sequence, set points and delays must be established by the responsible hazardous-area engineering and certification parties.
4. Ventilation, cooling and extraction
HVAC capacity must cover people, internal equipment, solar load and the project design ambient. If the module contains a fume hood, process exhaust or battery off-gas source, the supply and exhaust system must be designed together. Extraction can reduce internal pressure; pressurisation alone does not control a hazardous release created inside the module.
5. Fire, gas and emergency functions
Specify smoke, fire, flammable-gas and toxic-gas detection where required; fire suppression or host-system interfaces; emergency stop; emergency lighting; alarms; and evacuation arrangements. If an A-0 or A-60 boundary is required, identify the fire-rated walls, roof, floor, doors, dampers and penetrations that form that boundary.
6. Structural and transport requirements
For offshore service, define whether DNV 2.7-1 and EN 12079 are required, along with payload, lifting set, deck loads, sea fastening, transport limits and certification documentation. Hazardous-area compliance and offshore structural certification address different risks, so both scopes must be stated when needed.
Frequently Asked Questions
Does positive pressure make all internal equipment safe for a hazardous area?
No. Pressurisation can be part of the protection concept, but the entire system—including purge, pressure monitoring, alarms, shutdown, maintenance and failure conditions—must be designed and verified for its intended duty.
Can a pressurised container safely handle gas or chemicals released inside?
Not by pressure alone. Internal releases may require local extraction, gas detection, ventilation, suitable electrical equipment, emergency shutdown and process-specific controls. The risk assessment must distinguish external from internal hazards.
Is an A-60 container automatically suitable for Zone 1?
No. A fire rating and a hazardous-area protection concept are separate requirements. A module can need both, but one does not certify the other.
What should be included in the quotation request?
Include the application, installation location, zone classification, drawings, internal equipment data, utility details, environmental conditions, certification requirements, requested safety systems, dimensions, target delivery location and documentation requirements.
Build the Specification Around the Application
TLS supplies custom pressurised containers for offshore and onshore applications, including control rooms, electrical shelters and specialised process-support modules. Depending on the agreed project scope, systems can incorporate pressurisation controls, HVAC, fire-and-gas detection, passive fire protection and offshore structural certification. Send TLS your technical requirements for a project-specific solution.
