Unfortunately, they can also be highly flammable! As dryer lint is also highly flammable, and somewhere in your dryer there is a flame (or element) generating heat, you may want to think about swapping your current plastic flex hose for an aluminum flex hose or rigid pipe system.
Here's an eye-opening video on YouTube as to what can happen if you have a spark catch hold in your plastic flex hose:
Click Here for YouTube Video