Fire retardant is usually made from ammonium salts such as ammonium phosphate or ammonium sulfate, plus water and additives that help it spread, stick, and stay visible, like thickeners, corrosion inhibitors, and red dye.

What it contains

  • Active fire-slowing ingredient: often ammonium phosphate or ammonium sulfate.
  • Water: used to mix it into a sprayable liquid or slurry.
  • Thickeners: help it cling to plants or surfaces.
  • Corrosion inhibitors: protect equipment, especially aircraft tanks and parts.
  • Pigment or dye: usually red or pink so crews can see where it landed.

How it works

It slows fire by coating fuel, helping cool the surface, and making it harder for combustion to keep going. Some formulations also release water or other gases when heated, which helps suppress flames.

Important distinction

“Fire retardant” can mean different things depending on context: wildland firefighting drops, or chemical additives built into materials like foam, plastic, and textiles. In everyday conversation, people often mean the red aerial wildfire retardant.

One-line version

For wildfire use, fire retardant is basically a fertilizer-like chemical mix in water, plus dye and stabilizers, designed to slow or stop flames.