Understanding photoluminescent grades (DIN 67510)

Photoluminescent ("glow in the dark") signage is graded under DIN 67510 in the UK and Europe. The four grades — A, B, C, D — represent different luminance performance, and choosing the right grade affects both compliance and lifecycle cost.

What's being measured

DIN 67510 measures luminance (brightness in mcd/m²) at 10 minutes and 60 minutes after a controlled charge. Higher numbers = brighter for longer. Testing is done in a standardised lab, so different manufacturers' products are directly comparable.

The grades

• Grade A — minimum 23 mcd/m² at 10 min, 3.5 mcd/m² at 60 min. Entry-level. Adequate for short-duration emergency egress where charging conditions are reliable.
• Grade B — minimum 50 mcd/m² at 10 min, 7 mcd/m² at 60 min. Roughly 2x Grade A. Common workplace-grade specification.
• Grade C — minimum 140 mcd/m² at 10 min, 20 mcd/m² at 60 min. ~3x Grade B. Used in higher-risk environments where extended visibility is required.
• Grade D — minimum 300 mcd/m² at 10 min, 45 mcd/m² at 60 min. Highest performance. Specified in tunnels, mass-transit, and critical-egress applications.

When each grade is appropriate

• Standard offices, retail, hospitality: Grade B is typically adequate for workplaces with reliable lighting infrastructure
• Healthcare, schools: Grade C provides margin for areas where occupants may be impaired (anxiety, mobility, age)
• Industrial, manufacturing: Grade C or D depending on lighting reliability and worker proximity to ignition sources
• Tunnels, mass-transit, critical infrastructure: Grade D — extended luminance is essential when egress distances are long
• BESS / Energy substations: Grade C-D depending on remote location and emergency response timing

What charging the sign actually means

Photoluminescent signs charge under ambient light — they need adequate light during normal operation to glow when lights fail. Standard charging condition: 1000 lux (typical office lighting) for at least 15 minutes. Signs in dim corridors with intermittent lighting may not charge fully, which is why correct specification matters for the actual deployment environment.

For background, see our photoluminescent signs explained guide. Direct Signs supplies all four DIN 67510 grades with documented test certification.