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Flammability of Enclosures: Why the Material Grade Is a Safety Claim
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IEC 61010 addresses fire risk from two directions: by limiting the energy available and by requiring that enclosure materials resist ignition and do not propagate flame. The second is a material property, and it has to be evidenced, not assumed from the colour or from a supplier datasheet summary.
What the requirement asks
Enclosure materials are assessed for flammability class, usually against a well-known vertical burn classification, and the class required depends on the likelihood of ignition inside the enclosure and on whether the enclosure is the only barrier. A small enclosed transformerless supply in a plastic case is a different case from a metal chassis with a plastic bezel.
Evidence
The evidence is a material certificate from the resin or moulding supplier, with the class and the thickness at which the class applies. A class quoted for a 3 mm specimen does not automatically apply to a 1.5 mm wall. Wall thickness is part of the claim, and thin sections are exactly where mouldings burn.
Where the assessment goes wrong
Recycled or regrind material, and colour changes, can alter the flammability performance. A supplier who switches resin grade to meet a price target without telling the equipment manufacturer invalidates the safety evidence silently. Requiring a material declaration with each production batch is the only practical control.
