What Are Hazardous Substances? Their Effect on Ventilation Design
Updated: Sep 7
Ventilation design should start from "how is this substance classified" rather than "how much smoke or dust is there" — because two visually similar amounts of fume can call for very different exposure limits.
The Basis of Classification
Regulation (EC) No 1272/2008 (CLP), aligned with GHS, defines a classification and labelling system covering physical hazards (flammable, explosive — including dust and vapour) and health hazards (toxic, carcinogenic, sensitising, irritant). A substance's Safety Data Sheet (SDS) should be the starting point for design.
How Classification Drives Design
Substances with low exposure limits demand a lower residual concentration target, and therefore higher capture efficiency and/or higher extraction rates. Sensitising substances (certain isocyanates, some flux fumes) call for a near-zero-tolerance approach, because sensitisation can occur below the general exposure limit, and once a person is sensitised, any further exposure can worsen the reaction. Flammable or explosive substances directly determine ATEX classification and equipment selection.
Conclusion
Two visually similar smoke or dust sources can call for entirely different design requirements depending on substance classification; correct design starts with material identification and an SDS review, not a visual assessment.
Frequently Asked Questions
Can design be based on appearance alone? — No, it requires SDS/material analysis. What does CLP determine? — A substance's physical and health hazard classification and labelling.
References
● Regulation (EC) No 1272/2008 — CLP classification, labelling and packaging.
● General SDS/GHS implementation references.
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