Nomex® is the brand name for an inherently flame-resistant aramid fiber that is manufactured by DuPont™. It was invented by a Scottish-born scientist by the name of Dr. Wilfred Sweeny (1926–2011).
Technically, it’s referred to as a ‘synthetic aromatic polyamide polymer’. This basically means that it’s a man-made textile whose molecules are bonded extremely tight and close together in a chain-like structure.
This chain-like structure makes the fibers immensely strong, and it’s what makes Nomex® inherently flame-resistant. This means that the fiber itself is not flammable, making the protection permanent. It’s built into the fiber itself, so it can never be worn off or washed out.
Ok, so just how does this protect the wearer?
The aramid fibers swell and become thicker, when exposed to flame. This swelling helps to create a protective barrier between the wearer and the flame. And even though Nomex® will burn if you were to hold a flame up to it; as soon as the flame is removed it stops burning. Due to the way Nomex® is woven so thick and tightly together, makes it almost impossible for the fire to continue burning once the flame is removed from the material.
Think of it this way, the fire itself requires oxygen to continue burning. If we take away that oxygen and smother the fire with a blanket, for example, it will go out.
(Faqs – Nomex-Industrial, 2019)