UL 94-2021 pdf free download.Tests for Flammability of Plastic Materials for Parts in Devices and Appliances.
For the purpose of this Standard, the following definitions apply (See ISO 13943):
3.1 Afterfiame — Flame which persists after the ignition source has been removed.
3.2 Afterfiame Time — The length of time during which an afterflame persists under specified conditions.
3.3 Afterglow — Persistence of glowing combustion after both removal of the ignition source and the cessation of any flaming.
3.4 Afterglow Time — The length of time during which an afterglow persists under specified conditions.
3.5 Flame — To undergo combustion in the gaseous phase with emission of light.
3.6 Glowing Combustion— Combustion of a material in the solid phase without flame but with emission of
light from the combustion zone.
4 SignIficance of Tests
4.1 Tests conducted on a material under the conditions specified are intended to provide information when: comparing the relative burning characteristics of different materials, or assessing any change in burning characteristics prior to. or during, use. This method is not intended to provide correlation with performance under actual service conditions.
4.2 Assessment for risk of fire shall take into account such factors as fuel contribution, intensity of burning (rate of heat release), products of combustion and environmental factors such as the intensity of source, orientation of exposed material and ventilation conditions.
4.3 Burning characteristics, as measured by these test procedures, are affected by such factors as:
density, color, any anisotropy of the material molding conditions and the thickness of the specimen.
4.4 When a specimen of a thin matenal shrinks from the flame without igniting, the test results shall be deemed invalid and additional specimens shall be tested. If all test specimens shrink from the applied flame without igniting, these materials cannot be evaluated by the test procedure and an alternate test procedure in this Standard shall be conducted.
5 Apparatus
5.1 Laboratory Fume Hood — The laboratory fume hood chamber shall have an inside volume of at least
0.5 m3. The chamber shall permit observation of tests in progress and shall be draft free, while allowing a normal thermal circulation of air past the test specimen during burning. The inside surfaces of the chamber shall be of a dark colOr. When a light meter, facing towards the rear of the chamber, is positioned in place of the test specimen, the recorded light level shall be less than 20 lx. For safety and convenience, it is desirable that the enclosure (which can be completely closed) be fitted with an extraction device, such as an exhaust fan, to remove products of combustion which may be toxic. The extraction device shall be turned off during the test and turned on immediately after the test to remove the fire effluents. A positive closing damper may be needed.UL 94 pdf download.