What is generally not classified as a source of ignition?

Dryer vents are generally not classified as a source of ignition because, in typical use, they do not produce heat or sparks that can ignite flammable materials. Instead, dryer vents are designed to expel hot air and moisture from the dryer, and when maintained properly, they should not pose an ignition risk.

In contrast, open flames, sparks from machinery, and electrical equipment malfunctions are all potential sources of ignition. Open flames can ignite flammable vapors immediately upon contact. Sparks generated by machinery often occur due to friction, which can ignite combustible materials nearby. Similarly, malfunctions in electrical equipment can produce heat, sparks, or arcs that can easily ignite flammable substances. Therefore, identifying dryer vents as not being a source of ignition highlights their function and the importance of proper maintenance to ensure safety in environments where flammable materials are present.