What are IMO A.752(18) and ISO 15370:2021 standards for low location lighting?

IMO Resolution A.752(18) and ISO 15370:2021 are the two primary international standards governing low location lighting systems on ships. A.752(18) is the foundational IMO resolution that established the original performance requirements for photoluminescent escape route marking, while ISO 15370:2021 is the current technical standard that supersedes earlier versions and covers both photoluminescent and electrically powered low location lighting systems in greater detail. Together, they define how ships must guide passengers and crew to safety when smoke fills corridors during an emergency.

The sections below unpack the key differences between the two standards, which vessels must comply, what performance thresholds apply, and how shipbuilders can approach compliance efficiently.

How do IMO A.752(18) and ISO 15370:2021 differ from each other?

IMO Resolution A.752(18) is the mandatory policy framework adopted by the International Maritime Organization in 1993, setting the requirement for low location lighting on passenger ships. ISO 15370:2021 is the detailed technical standard that specifies exactly how a low location lighting system must be designed, tested, and installed to meet those requirements. In practical terms, A.752(18) tells you what must be achieved; ISO 15370:2021 tells you how to achieve it.

A.752(18) was groundbreaking when introduced because it recognized that smoke accumulates at ceiling level first, leaving a cleaner air layer close to the floor. By marking escape routes at a low level, occupants who are crawling or crouching can still follow a visible path. The resolution applies broadly and is incorporated into SOLAS Chapter II-2.

ISO 15370:2021 is the most recent revision of the technical standard and reflects advances in both photoluminescent materials and LED technology. It introduces stricter luminance thresholds, updated test methods, and formal requirements for electrically powered systems alongside photoluminescent ones. For shipbuilders and project managers, ISO 15370:2021 is the document that governs the actual specification and procurement of compliant products.

Which ship types and spaces must comply with these LLL standards?

The primary obligation under IMO A.752(18) and ISO 15370:2021 applies to passenger ships, including ro-ro passenger vessels, as defined under SOLAS. Specifically, all escape routes, stairways, corridors, and muster stations on these vessels must be fitted with a compliant low location lighting system. High-speed craft carrying passengers and certain cargo ships also fall within scope depending on flag state requirements.

Within a vessel, the spaces that must be marked include:

• Corridors and passageways forming part of the escape route
• Stairway enclosures and staircase treads
• Muster and embarkation stations
• Doorways and exits along escape routes
• Open deck areas used for evacuation

Flag states and classification societies such as DNV may extend requirements to additional vessel types or spaces. Offshore installations and naval vessels often adopt the same standards voluntarily or through their own regulatory frameworks. If you are managing a newbuild project, confirming scope with the relevant flag state authority early in the design phase avoids costly retrofits later.

What are the performance requirements for low location lighting systems?

ISO 15370:2021 sets minimum luminance levels that a low location lighting system must maintain under defined conditions. For photoluminescent systems, the standard specifies the minimum luminance output after a set charging period and after a defined period in darkness, ensuring the system remains visible throughout a realistic evacuation scenario. Electrically powered systems must maintain continuous illumination for a minimum duration even when the main power supply fails.

Key performance criteria include:

• Luminance threshold: Photoluminescent materials must meet minimum mcd/m² values after a full charge and after extended darkness periods
• Charging requirements: Systems must reach performance levels under normal shipboard lighting conditions without special charging equipment
• Backup duration: Electrically powered systems must operate on emergency power for the duration specified by SOLAS requirements
• Environmental resistance: Materials must withstand marine environments including humidity, salt spray, UV exposure, and temperature extremes
• Installation height: Marking must be positioned at or near floor level, typically with the top edge no higher than 300 mm above the deck

Products that exceed these thresholds offer a meaningful safety margin. Our New Generation IMO products, for instance, are manufactured to exceed standard luminance requirements by a factor of four, providing a substantially brighter escape path under real emergency conditions.

What is the difference between photoluminescent and electrically powered LLL systems?

Photoluminescent low location lighting systems absorb ambient light and re-emit it as a visible glow when the surrounding environment becomes dark. Electrically powered systems use LED strips connected to the vessel’s emergency power supply to produce active illumination. The fundamental difference is the energy source: photoluminescent systems are passive and require no wiring, while electrically powered systems provide consistent, controllable light output regardless of prior charging conditions.

Photoluminescent systems (3L-PL™)

Photoluminescent systems are lightweight, straightforward to install, and require no electrical infrastructure. They are well suited to vessels where cable routing is complex or where minimizing installation cost and weight is a priority. The limitation is that performance depends on the quality and duration of prior light exposure. In spaces with low ambient lighting or where the system may not receive an adequate charge, output after extended darkness can fall below optimal levels.

Electrically powered systems (3L-EP™)

Electrically powered LED systems deliver consistent illumination from the moment power is applied and maintain that output for the full duration of emergency power availability. Our 3L-EP™ system, for example, provides reliable lighting across runs of up to 1,000 metres without interruption. This makes electrically powered systems the preferred choice for large passenger vessels, long escape routes, and spaces where charging conditions for photoluminescent materials cannot be guaranteed. The trade-off is the need for wiring, power connections, and periodic electrical maintenance.

How does compliance with IMO A.752(18) and ISO 15370:2021 get verified?

Compliance is verified through a combination of product certification, installation inspection, and flag state or classification society approval. Products must be type-approved against ISO 15370:2021 test requirements before installation. Once fitted, the installed system is inspected to confirm correct positioning, continuity of marking, and overall coverage of all required escape routes.

Classification societies such as DNV conduct onboard inspections as part of the vessel’s statutory survey process. For photoluminescent systems, inspectors verify that materials carry valid type approval and that installation meets the standard’s dimensional requirements. For electrically powered systems, functional testing of the emergency power connection and illumination output is also required.

We provide 3L-SI™ inspections carried out by our DNV-certified inspectors, who assess system condition, verify documentation, and confirm ongoing compliance. This is particularly valuable during newbuild delivery inspections and periodic surveys, where a formal compliance record supports the vessel’s certification process and reduces the risk of deficiencies being raised by port state control.

When should shipbuilders choose a turnkey LLL solution over sourcing components separately?

Shipbuilders should choose a turnkey low location lighting solution when project complexity, timeline pressure, or the need for certified compliance documentation makes coordinating multiple suppliers a risk. A single turnkey provider handles design, supply, installation, and verification under one contract, eliminating the gaps that can appear when different parties supply components that have not been tested or specified together.

Sourcing components separately can appear cost-effective at the quotation stage, but it introduces several practical risks:

• Incompatible products from different suppliers may not collectively meet ISO 15370:2021 system-level requirements even if each component is individually certified
• Responsibility for overall system compliance becomes unclear when multiple vendors are involved
• Coordination across design, procurement, and installation phases adds project management overhead
• Rectifying non-compliance identified during final inspection is significantly more expensive than designing correctly from the start

A turnkey approach is especially well suited to newbuild projects with tight delivery schedules, vessels operating across multiple flag state jurisdictions, and operators who want a single point of accountability for their low location lighting system throughout its service life. For projects where compliance documentation needs to be complete and auditable from day one, the turnkey model consistently delivers lower total risk than a fragmented supply chain.