Flammability is the area where laboratories most often buy the wrong instrument. Not because the equipment is complicated, but because the standards are chosen by what the product is and where it will be sold — and that information usually arrives after the purchase.
The geometry is the method
Every flammability standard fixes three things: how the specimen is held, where the flame touches it, and what you measure. Change any of them and you have a different test with a different pass criterion.
| Orientation | Typical standards | Product types |
|---|---|---|
| Vertical | ISO 6940 / 6941, ASTM D6413 | Protective clothing, workwear |
| Vertical, hanging | NFPA 701 | Drapery, curtains, hanging textiles |
| 45° | ASTM D1230 | General apparel (US market) |
| Horizontal & vertical | IEC 60695-11-10 (UL 94) | Plastics, electrical enclosures |
A vertical flame travels upward through its own preheated zone, so vertical tests are the most severe. A horizontal flame has to work against gravity and is the least severe. The 45° tests sit between them. This is why a fabric can pass a 45° apparel test and fail a vertical protective clothing test — the physics changed, not the fabric.
Ease of ignition is not flame spread
Two closely numbered ISO standards are routinely confused.
- ISO 6940 — ease of ignition. How long does the flame have to be applied before the specimen ignites?
- ISO 6941 — flame spread. Once it is alight, how fast does the flame travel a measured distance?
A fabric can be hard to ignite and then burn quickly, or ignite instantly and self-extinguish. These are separate properties and separate acceptance criteria. Specifications that name only "ISO 6940/6941" without saying which measurement applies are incomplete.
UL 94 is not a textile standard
UL 94 — published internationally as IEC 60695-11-10 and related parts — classifies plastics and polymer components: enclosures, connectors, printed circuit substrates, foams.
It uses two burner ratings (a lower-energy and a higher-energy flame), horizontal and vertical configurations, and produces classifications such as HB, V-0, V-1, V-2 and 5VA/5VB. The apparatus needs controlled gas flow, a defined burner tube geometry and precise timers, because the classification depends on afterflame times measured to a fraction of a second.
If your product is a textile, UL 94 is the wrong standard. If your product is the plastic housing that the textile is fitted into, it is the right one — and a textile flammability cabinet cannot run it.
Sector rules override general standards
Before selecting a general test, check whether the sector imposes its own:
- Automotive interiors — horizontal burn rate methods are the norm.
- French M-classification — the NF P 92-50x series for building and fitting materials, including electrical burner and radiant panel configurations.
- Upholstered furniture — ignition source tests using cigarettes and simulated matches.
- Carpets and floor coverings — radiant panel and pill tests.
- Blankets and bedding — dedicated methods with their own specimen mounting.
These exist because the fire scenario differs. A curtain ignites at its hem from below; a car headliner is exposed from the side; a carpet burns under radiant heat from a room fire. No single cabinet covers them all.
Practical questions before you buy
- Which markets? EU, US and national schemes rarely accept each other's results.
- Which product category? Apparel, protective clothing, drapery, upholstery, automotive, plastics — each pulls a different standard.
- Which gas? Most methods specify the fuel gas and its purity. Methane, propane and butane produce different flame temperatures and are not interchangeable.
- Extraction and safety. These tests produce smoke and combustion products. An extraction fan and a fire-safe cabinet position are part of the installation, not accessories.
- Calibration of the flame. Flame height and burner angle are specified to the millimetre and degree. An instrument without a flame height gauge cannot be verified.
The most expensive mistake in this area is buying a cabinet that runs the standard you have today, then discovering the export customer requires a different orientation. Ask for the standards list from sales and regulatory before specifying, not after.
Reporting
Name the standard including its part or method number, the burner and gas used, the specimen orientation, and the flame application time. A flammability report without those four is not auditable — and flammability is exactly the area where an auditor will ask.