The UL 94 test is a laboratory standard for testing the flammability of plastics, published by Underwriters Laboratories (also known as UL). The goal of this test is to evaluate the flammability of plastic materials. For this reason, the test is not usually applied to metallic materials, such as stainless steel.
Stainless steel is extremely flame resistant, and methods that simulate thermal decomposition or combustion do not make sense for this material. As a result, you will not typically see information about UL 94 testing for stainless steel or other metals.
Note, however, that while stainless steel itself is highly resistant to ignition, other materials combined with it, such as insulation or coatings behind panels, may still need to be tested for combustion to meet safety and code requirements.
If your product contains stainless steel and other tightly bonded materials, it may be necessary to seek specialised acceptance testing for flame resistance or flame retardancy based on specific applications and safety standards. It may be necessary to seek advice from a specialist testing and certification body as to which test method should be used and which material is suitable for which method.