What Is Included in a Zone 1 or Zone 2 A60 Pressurised Container

Short Summary

A Zone 1 or Zone 2 A60 pressurised container is an engineered enclosure that combines several separate protection functions. Hazardous-area classification defines the external gas risk.

Pressurisation and ventilation help protect the internal room and equipment. A60 construction provides a tested passive-fire boundary. Fire and gas detection, shutdown logic, dampers, HVAC, electrical equipment and external interfaces make the protection concept work. The required certificates and their boundaries must be agreed for each project.

The Short Answer

A typical TLS pressurised container can be configured with an A60-rated enclosure, a pressurisation and HVAC system, fire and gas detection, a combined control panel, emergency shutdown functions, automatic dampers, electrical distribution, lighting, alarms and project-specific utility interfaces.

These elements do different jobs. Zone classification, A60 fire rating, offshore-container certification and Ex certification are not interchangeable. A certificate for the structure or one component does not automatically certify the complete installed module for every location.

What Zone 1 and Zone 2 Mean for the Container

IEC 60079-10-1 covers classification of areas where flammable gas or vapour hazards may arise. The site owner normally determines the zone from release sources, ventilation and operating conditions.

In practical terms, Zone 1 represents a location where an explosive gas atmosphere is likely to occur occasionally in normal operation. Zone 2 represents a location where it is not likely in normal operation and, if it occurs, is expected to persist only briefly. The classification must also identify the gas or vapour, equipment group, temperature class and other installation conditions that affect equipment selection.

The container supplier should receive the approved hazardous-area dossier. TLS should not infer a Zone 1 or Zone 2 requirement from the industry or site name alone.

What A60 Means

A60 is a passive structural fire-protection classification used in marine and offshore applications. It concerns the tested fire resistance and insulation performance of the division for 60 minutes under the applicable fire-test procedure.

An A60 boundary is only effective when its walls, roof, floor, doors, windows, penetrations, dampers and installed details preserve the approved construction. A later cable transit, duct opening or equipment support can compromise the boundary if it is not designed and installed as part of the approved arrangement.

A60 does not mean blast-rated, gas-tight, smoke-proof, explosion-proof or suitable for a hazardous area by itself. Those functions require separate specifications and evidence.

How Positive Pressurisation Protects the Internal Space

IEC 60079-13 addresses equipment protection by pressurised rooms and artificially ventilated rooms. A pressurised room uses protective air to establish and maintain an internal pressure that limits entry of the external explosive atmosphere.

The functional sequence normally includes:

Confirm that doors and relevant openings are closed.
Supply air from a defined safe source.
Purge the room at the required airflow for the calculated time or volume exchange.
Prove airflow or pressure with monitored devices.
Permit energisation of protected non-Ex equipment only after the required conditions are satisfied.
Maintain pressure during operation.
Alarm and take the specified action if pressure, airflow or safe-air quality is lost.

The response to a fault is a project decision governed by the protection concept. It may include an alarm, delayed shutdown, immediate isolation of nonessential or non-Ex circuits, damper closure or another defined safe-state sequence. Personnel safety, continuity requirements and the consequences of de-energisation must be considered together.

What the HVAC and Air System Can Include

The HVAC package manages heat, temperature, humidity and air distribution while supporting the pressurisation philosophy. Depending on the design, the package can include:

duty or duty-standby pressurisation fans;
filtered fresh-air intake from a defined safe location;
heating or cooling equipment sized from the room heat load;
supply and return ductwork;
pressure-relief or overpressure dampers;
fire and gas shut-off dampers;
airflow, differential-pressure and filter-status monitoring;
non-return devices and leakage-control details; and
local and remote status signals.

The air intake location is a safety interface. A container cannot maintain a safe internal atmosphere if its protective-air source can ingest the same gas release that created the hazardous area. The site designer must define the intake position, duct route and required gas detection.

HVAC cooling and room pressurisation are related but not identical. Cooling capacity is selected from ambient conditions and internal heat gains. Protective airflow and purge performance are selected from the pressurisation assessment. Both must be verified without assuming that one fan rating satisfies both functions.

Fire and Gas Detection

TLS pressurised-container solutions can include a combined pressurisation, fire and gas control system. The detection package may include combustible-gas detectors, toxic-gas detectors where required, smoke or heat detection, manual alarm devices and external interface points.

Detector type, quantity and location depend on the identified hazards. The specification should state:

target gases and sensor technologies;
detector measuring ranges and alarm setpoints;
voting philosophy, if any;
internal and external detector locations;
alarm, shutdown and ventilation actions;
detector certification and environmental rating;
calibration and maintenance access; and
interfaces with the platform or plant fire and gas system.

Gas detection does not replace area classification, safe-air-source design or certified electrical equipment where those controls are required.

Emergency Shutdown and Control Logic

The control panel coordinates purging, pressurisation, alarms, equipment permissives and shutdown actions. The project cause-and-effect document should show how each input affects fans, dampers, HVAC, normal power, protected equipment, emergency lighting and remote alarms.

Common inputs can include high gas, smoke or fire, low room pressure, low airflow, fan failure, damper position, door status, high internal temperature and manual emergency stop. Common outputs can include audible and visual alarms, power isolation, fan changeover, intake closure, HVAC shutdown and signals to the host installation.

An emergency stop button is only one input. A complete ESD function also requires a defined isolation boundary, suitable switching devices, fail-safe behavior, reset conditions and coordination with the facility's ESD hierarchy.

Dampers Doors and Penetrations

Dampers and doors are active parts of the protection concept. Fire dampers preserve the fire boundary at ventilation openings. Gas-tight or shut-off dampers isolate air paths when the control logic detects an unsafe condition. Pressure-relief devices prevent excessive room pressure. Their fire rating, Ex suitability, fail position, actuation method, status feedback and reset method should be specified.

Doors may require self-closing hardware, seals, hold-open restrictions, panic hardware, interlocks or an airlock, depending on the application. Every cable, pipe and duct penetration must be coordinated with A60 integrity, environmental sealing, hazardous-area requirements and future maintenance.

Electrical Systems

The electrical package can include an incoming isolator, distribution boards, transformers where required, normal and emergency lighting, sockets, equipment feeders, earthing and bonding, alarms and external connection points.

The hazardous-area strategy determines which external and exposed components need appropriate Ex protection. Pressurisation may allow specified equipment inside the protected room to be non-Ex only when the complete protection sequence and fault response meet the applicable requirements. Equipment that remains energized before purge, during loss of pressure or outside the protected room must be selected for its actual location and duty.

Voltage, frequency, fault level, earthing system, short-circuit ratings, cable entries, segregation, emergency supply and power-isolation philosophy are project inputs. They are not implied by the words Zone 1, Zone 2 or A60.

Certification Boundaries

A compliant module may require several different evidence packages:

structural and lifting certification for the offshore container and lifting set;
fire-test or type-approval evidence for the A60 construction and its installed details;
hazardous-area certification for individual electrical and mechanical equipment;
assessment of the pressurised-room protection system;
inspection and test records for the assembled module; and
acceptance by the owner, class society, flag administration or local authority, as applicable.

DNV-ST-E271, commonly known as DNV 2.7-1, addresses offshore containers and lifting sets, including manufacture, testing, marking and periodic inspection. It does not by itself approve the pressurisation logic, A60 boundary, electrical installation or the process equipment inside the container.

Likewise, an ATEX, IECEx or other Ex certificate for a fan, detector or switch does not certify the entire room. The purchase specification should state the required conformity route, certifying body, certificate holder, document deliverables and whether assessment covers the design, production unit or complete installed system.

Buyer Inputs for a Useful RFQ

Provide the following information:

installation location and onshore, offshore, vessel or platform context;
approved Zone 1 or Zone 2 classification, gas group and temperature class;
identified flammable and toxic gases and the area-classification dossier;
required A60 boundary faces and exposure direction;
offshore structural, lifting and certification requirements;
room use, occupancy, personnel count and installed equipment;
equipment dimensions, weights, heat loads and maintenance clearances;
ambient temperature, humidity, solar load, salt, dust and corrosion conditions;
safe-air intake location and maximum duct route;
required room pressure, purge philosophy and loss-of-pressure action;
fire and gas detector list, setpoints and cause-and-effect requirements;
ESD hierarchy, isolation boundary and host-system interfaces;
supply voltage, frequency, fault level, earthing and emergency power;
cable, pipe, ventilation and communications penetrations;
required utility connections and drainage;
applicable standards, class, flag and authority requirements;
FAT, witness, documentation, installation and site-test requirements; and
transport dimensions, mass limits, lifting method and destination.

TLS engineering should confirm the final ventilation rates, pressure setpoints, purge time, detector arrangement, shutdown logic, HVAC duty, electrical ratings, penetration details, certification route and site interfaces.

Frequently Asked Questions

Does positive pressure make every item inside non hazardous

No. The protection concept must establish purge and pressure before specified equipment is energized and must define what happens during a fault. Equipment energized outside that protected condition must suit its actual hazardous location.

Is Zone 1 simply a higher specification version of Zone 2

No. The different frequency and duration assumptions affect the protection concept, equipment category or equipment protection level, fault response and assessment. The approved site classification controls the design.

Does A60 mean the container is explosion proof

No. A60 is a passive fire-resistance classification. Explosion protection, blast resistance, gas tightness and hazardous-area electrical suitability are separate requirements.

Is DNV 2.7-1 certification enough for offshore use

It confirms a defined offshore-container and lifting scope. Operational use can also require A60, hazardous-area, electrical, fire and gas, process, flag, class and installation approvals.

What happens when room pressure falls

The agreed cause-and-effect logic governs the response. It can include alarms, time delays, isolation of selected circuits, damper actions and remote signals. The response must be designed for the equipment, occupancy and facility safety philosophy.

Can TLS provide a Zone 1 or Zone 2 A60 module for different uses

TLS can configure pressurised modules for applications such as laboratories, workshops, control rooms and electrical shelters. Layout, installed systems and evidence are engineered for the stated use and project requirements.

Request a Defined Pressurised Container Scope

Send TLS the hazardous-area dossier, A60 boundary requirement, equipment heat loads, fire and gas philosophy, ESD cause and effect, electrical data and certification route. TLS can develop a project-specific module scope and identify the interfaces that remain with the buyer or host installation.