What does the flammable sign indicate?

The flammable sign indicates that a substance is capable of catching fire and burning easily when exposed to an ignition source. This is crucial information for anyone handling or working near such materials, as it alerts them to the potential risks associated with the substance.

When a material is marked with a flammable sign, it generally means that it can ignite quickly in the presence of a spark, flame, or even high temperatures. Therefore, understanding this labeling is essential for ensuring the proper handling and storage of flammable materials to prevent accidents and injuries.

The other options mentioned do not accurately describe the core characteristic represented by the flammable sign. For instance, the potential for combusting upon contact with air pertains more specifically to certain reactive substances rather than flammable ones. Similarly, the risks of explosions under pressure and chemical burns relate to different hazards and are indicated by other specific warning signs or labels.