How Photoluminescent Safety Signs Are Measured: Understanding DIN 67510

What the test actually involves, what mcd/m² figures on a datasheet really tell you, and how to compare products fairly. · 4 min read

The Problem the Standard Solves

When the lights go out on a vessel, an offshore platform, or in any commercial building, an evacuation route is only as safe as the signs guiding people through it. Every photoluminescent sign manufacturer can claim their products "glow in the dark" — but without a controlled test method, those claims have no comparative meaning. A sign that glows brightly for two minutes is not the same product as one that maintains usable visibility for an hour, and a buyer needs a way to tell them apart.

DIN 67510 is the standard that provides that comparison. It sets out how the afterglow performance of photoluminescent materials is measured and how products are sorted into performance classes — from entry-level indoor signs at one end up to the high-performance grades specified for maritime, tunnel, and heavy industrial applications at the other.

Why DIN, Specifically

DIN 67510 is a German national standard, but its influence reaches well beyond Germany. It was the first widely adopted measurement framework for photoluminescent products, and it became the de facto international reference long before equivalent ISO standards emerged. Today it underpins related international work, including ISO 17398 on classification and durability of safety signs and ISO 16069 on graphical safety way-guidance systems.

For a buyer or specifier, the practical meaning is this: if a product datasheet quotes DIN 67510 figures, you can compare it directly against any other product that quotes the same standard. That comparability is what the test exists to provide.

How the Test Works

The principle is straightforward. A sample of the photoluminescent material is charged under a defined light source — a calibrated lamp at a controlled illuminance, for a controlled duration. The light is then switched off, and the sample's luminance — its perceived brightness, measured in millicandelas per square metre (mcd/m²) — is recorded at fixed time intervals as it decays.

Measurement continues until the glow drops to roughly 0.3 mcd/m². That is not an arbitrary cut-off — it is the approximate threshold of human dark-adapted visibility. Below it, the human eye cannot reliably distinguish the glow from black, so further measurement adds nothing useful for safety purposes.

Reading a Datasheet

When you look at a datasheet for a photoluminescent product, three pieces of information do most of the work:

1. The Certified Class

This is the headline performance category — the standard sorts products into bands based on their measured decay performance. Higher classes mean brighter and longer-lasting glow. The class your application requires is usually driven by the regulation that applies to it: maritime applications under IMO guidance typically demand higher classes than general indoor signage.

2. The 10-Minute and 60-Minute Luminance Figures

These are the two specific data points that matter most for real-world performance. The 10-minute luminance tells you how the sign performs in the first critical phase of an evacuation, when most people are still finding their way out. The 60-minute luminance tells you how well it sustains visibility for prolonged emergencies — particularly important offshore, where evacuation timelines can stretch well beyond the first ten minutes.

A product can technically meet a class threshold while still performing notably better or worse than another product in the same class. The 10- and 60-minute figures let you see those differences directly.

3. The Certifying Body

A credible datasheet is backed by a test report from an accredited independent laboratory, not by self-measurement. If a quoted DIN 67510 figure does not reference the testing laboratory and report number, the figure is not verifiable — and unverifiable figures are essentially marketing.

Comparing Products Fairly

A few rules of thumb make supplier-to-supplier comparison much more reliable:

• Compare same-class to same-class first. A higher-class product will almost always beat a lower-class product on absolute figures, but the meaningful comparison is between products competing for the same specification.
• Look at the 60-minute figure, not just the 10-minute figure. Some products charge brightly but decay quickly. The 60-minute number reveals which products genuinely sustain performance and which only sprint.
• Check the test report exists. Ask for the laboratory name and report number. Reputable suppliers will provide both without hesitation; products without a verifiable report are best treated with caution.
• Match class to application, not the other way around. Buying a higher class than your specification requires costs more without delivering useful additional safety; buying lower is the kind of decision that fails an audit.

Where DIN 67510 Sits in the Wider Picture

DIN 67510 governs how a photoluminescent material is measured. It does not, by itself, tell you whether a sign is suitable for a particular application — that depends on the regulation governing the application (SOLAS, the FSS Code, ISO 15370 for maritime LLL, local building codes for shore-based escape signs), which in turn references the DIN classes or their ISO equivalents.

Treat DIN 67510 as the underlying performance language. The application-specific regulation tells you which level of that language you need to speak.