The Definition of Pyrophoric Material

Definition of Pyrophoric Material

A pyrophoric material is a substance that ignites spontaneously when exposed to air, without any external ignition source. Under OSHA's Hazard Communication Standard, which follows the GHS, pyrophoric liquids and solids are those that, even in small quantities, ignite within five minutes of contact with air. OSHA also defines a pyrophoric gas as one that ignites spontaneously in air at or below 130°F (54.4°C).

Common examples include alkyllithium reagents such as tert-butyllithium, diethylzinc, silane gas, white or yellow phosphorus, finely divided metal powders and iron sulfide scale that forms inside sour crude and natural gas equipment. Many pyrophorics also react violently with water.

Key Facts About Pyrophoric Materials

• GHS labels pyrophorics with the flame pictogram and the hazard statement "catches fire spontaneously if exposed to air."
• They are handled under inert gas, such as nitrogen or argon, or under solvent or oil.
• Iron sulfide fires are a known hazard when opening vessels, tanks and filters in oil and gas and refining.
• Flame-resistant lab coats or clothing, safety glasses and a face shield are standard PPE.
• Class D extinguishers or dry sand are used for many metal and pyrophoric fires; water can make some worse.

Example of a Pyrophoric Material

Maintenance crews open a sour gas separator for inspection. As air enters, iron sulfide deposits on the internals begin to glow and smoke. Following procedure, the crew keeps the deposits wet, removes them carefully and places them in water-filled drums for disposal.

How to Handle Pyrophoric Materials Safely

1. Review the safety data sheet and write a task-specific procedure.
2. Use inert atmosphere techniques, such as gloveboxes or sealed transfer systems.
3. Remove flammables and ignition sources from the work area.
4. Wear flame-resistant clothing and eye and face protection, and never work alone.
5. Keep the right extinguishing media nearby and keep equipment wet when opening systems that may contain iron sulfide.

Related Terms

• Chemical Hazard
• Explosion Hazard
• Ignition Source
• Fire Extinguisher Classes
• Oxidizer

Frequently Asked Questions: Pyrophoric Material

Is a pyrophoric material the same as a flammable material?

No. Flammable materials need an ignition source. Pyrophoric materials ignite on their own when they contact air.

Can you use water on a pyrophoric fire?

Usually not. Many pyrophorics also react with water. Use the extinguishing agent specified on the SDS, often a Class D extinguisher or dry sand.

Why is iron sulfide dangerous in oil and gas?

It forms inside equipment exposed to hydrogen sulfide. When the equipment is opened, the iron sulfide oxidizes rapidly, heats up and can ignite hydrocarbons.