Smart switch listings compete on glass finish, gang count, and how pretty the app is. The property that actually separates a serious product from a dangerous one is the material that holds the live parts - and it never appears in a photo. Buyers cannot judge flammability through a screen, which is why it has become the quiet gap between quotes that look identical and behave very differently during a fault.
Two tests, two different questions
Flammability gets tested two ways and they are not interchangeable. The UL94 burn test asks: if this material catches fire, does it self-extinguish, and does it drip burning material? The glow-wire test - with typical thresholds of 750 and 850 degrees Celsius - asks the opposite question: if a live part overheats against this plastic, will the plastic ignite at all? A housing can pass one and fail the other. Standards assign the relevant test per part and per current-carrying role, which is why "which rating applies" is a question about the part, not the product.
Which part must pass what
The load-bearing frame that carries terminal blocks, relays, and the mains-side board is the part that matters; it must meet the glow-wire threshold required for supports of live parts. Decorative front panels sit away from live parts and can be held to a lower requirement. The tempered glass face contributes nothing to fire behavior either way - glass does not burn - which is one more reason judging a switch by its front surface is useless. The honest spec sheet names the frame material and its rating separately from the panel finish.
PC, ABS, and the recycled third option
Polycarbonate is the standard choice: stable across the temperature range, available in naturally flame-retardant grades, dimensionally consistent over years. ABS is cheaper and easier to mold but needs additives to reach the same class, and those additives age. The third option never appears on a datasheet: recycled or unknown-origin resin, which can look identical and pass first-article inspection while drifting batch to batch. Recycled content is acceptable when it is specified and certified; it is a lottery when it is quiet. This is the material substitution that never shows up as a line item - it shows up as a slightly better unit price.
What it costs you
Glow-wire grade and resin choice interact with the certifications a product can claim, and the certifying body records the material in the file. Swap resin after certification and the certificate no longer describes the shipped product - some markets require the model on the certificate to match the model in the box. For an OEM buyer that means the flame spec belongs in the RFQ, not in a conversation after the sample arrives.
What to ask the factory
Five questions cover it. What is the frame resin and its glow-wire rating - 750 or 850? Is the panel resin specified separately? Is any recycled content certified with batch traceability? Which certifications does the current file cover, and does the shipped model appear on the certificate model list? And can the material spec be written into the purchase agreement itself? A factory that answers with numbers has nothing to hide; one that answers with adjectives is telling you where its margin came from. We publish material and certification answers for our smart switch range on the switch manufacturing page - see the factory overview or raise the question directly on the contact page.
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