Workers in oil and gas, electrical maintenance, and welding rely on Flame Resistant (FR) coveralls to protect them from flash fires and arc flashes. The physics of FR gear rely on either a chemical treatment embedded in the fibers (treated cotton) or the molecular structure of the fiber itself (Nomex, Modacrylic). The most common and deadly mistake in the maintenance of these garments is washing them with standard household detergents, bleach, or fabric softeners.
Standard household detergents often contain optical brighteners. These are chemicals that reflect UV light to make clothes look "whiter and brighter." While great for a t-shirt, optical brighteners are hydrocarbon-based and flammable. When you wash FR gear in detergent with brighteners, you are coating the fabric in a layer of fuel. In the event of a flash fire, these brighteners ignite instantly and can defeat the protective properties of the fabric, allowing the flame to spread across the garment.
Worse is the use of Bleach (Sodium Hypochlorite). Bleach is an aggressive oxidizer that attacks the chemical structure of FR-treated cotton and synthetic fibers. It destroys the flame-resistant bond in the polymer. After just a few washes with bleach, a coverall can become as flammable as a gasoline-soaked rag.
The Maintenance Protocol: Never wash FR clothing with any other types of clothes. Never use bleach, borax, or fabric softeners (which leave an oily, flammable coating). Use only mild, pH-neutral soaps specifically designed for technical gear or baby laundry (which is typically free of additives). If you accidentally wash your FR gear in bleach, or if you have used fabric softener on it, the garment is compromised and must be discarded immediately. You cannot wash the chemical contamination out; the flame resistance has been chemically broken.
