The terms "technical tightness" and "permanently technical tightness" with their underlying conceptual ideas have proven themselves for decades in occupational safety and health for the assessment of explosion hazards (and gas hazards) and the necessary protective measures. The joint working group of the Prevention Sections Chemistry and Machine and System Safety presents an internationally referencable document on technical tightness, which can be referred to after the terms in DIN EN 1127-1 have been omitted.