Flame-resistant (FR) clothing is designed to resist ignition, slow down the burning process, and self-extinguish once the ignition source is removed. The flame resistance in these garments can be achieved in two primary ways:
1. Inherent Flame Resistance
Some materials are naturally flame resistant due to the properties of the fibers from which they are made. These fibers, including aramid, modacrylic, and melamine, are engineered to be flame resistant at the molecular level. This means that flame resistance is a built-in property of the fiber and will not wash out or wear away over time.
Examples of such inherently flame-resistant fibers include:
- Nomex: A type of aramid fiber used in FR clothing for firefighters, industrial workers, and pilots.
- Kevlar: Another type of aramid fiber, often used in cut-resistant and heat-resistant gloves, as well as in body armor.
- PBI (Polybenzimidazole): A high-performance fiber used in high heat environments, such as firefighting.
2. Treated Flame Resistance
Other materials are made flame resistant through a chemical treatment process. These fabrics are typically made from cotton or a cotton blend and then treated with a flame-retardant chemical. Over time and with continuous washing, the effectiveness of the flame-retardant treatment can diminish, so these garments often have a defined lifespan after which they should be replaced.
Examples of chemically treated fabrics include:
- Indura and UltraSoft: These are types of cotton or cotton-blend fabrics that have been treated with a flame-retardant chemical.
- Proban / FR-7A: These are cotton fabrics treated with a phosphonium salt condensate, which becomes a flame-retardant polymer when cured.
Whether inherently flame resistant or treated for flame resistance, all FR clothing is designed to resist ignition, prevent the spread of fire, and protect the wearer from heat and flames. However, it’s important to remember that no clothing is completely fireproof, and FR clothing is intended to give the wearer time to escape from a fire-related hazard, not to go into or stay in a fire.