Pyrophoric Gases and Liquids

Spontaneous Heating and Pyrophoricity

DOE-HDBK-1081-94

PYROPHORIC GASES AND LIQUIDS

PYROPHORIC GASES AND LIQUIDS

Pyrophoric Gases

There are several kinds of pyrophoric gases that should be included in any discussion of

pyrophoricity. Many of these are used in manufacturing microelectronics. All of the gases

presented here have 3 things in common: a) they can ignite immediately upon exposure to

air, b) they are all nonmetallic hydrides, and c) many other compounds which contain these

gases in their molecular structure are also pyrophoric.

Arsine

Arsine (AsH3 ), also know as arsenic hydride, is a colorless, highly toxic gas with a

distinctive garlic-like odor. It is heavier than air and is a blood and nerve poison.

Arsine will generally not ignite in air unless at elevated temperatures, but it can be

detonated by a suitably powerful initiation (heat source, shock wave, electrostatic

discharge). Arsine may also exist in other compounds. The ignition temperature of

many of these arsine containing compounds is lower than that of arsine, causing

them to ignite in air even at low temperatures (below 0 C, 32 F). All arsine

compounds should be considered pyrophoric until they are properly characterized.

Diborane

Diborane (B2H6) is a highly toxic, colorless gas with a repulsive but sweet odor; it is

highly reactive and flammable. It forms flammable mixtures with air over a wide

range (flammable limits, 0.9% and 98%). The ignition temperature of diborane is

between 38 and 52 C (100 and 125 F). Diborane will ignite spontaneously in moist

air at room temperature. It reacts spontaneously with chlorine and forms hydrides

with aluminum and lithium, which may ignite spontaneously in air. It reacts with

many oxidized surfaces as a strong reducing agent, and reacts violently with

vaporizing liquid-type extinguishing agents.

Storage should be in a detached, refrigerated (less than 20 C, 68 F), and well-

ventilated place. Boranes should be separated from halogens and other oxidizing

agents and checked periodically for decomposition. Protect against electrical spark,

open flames, or any other heat source. A dry nitrogen purge should be used in any

transfer. Waste material should be completely hydrolyzed with water before

disposal. Combustible solutions should be burned as a means of disposal. There are

no special shipping requirements for diborane other than steel pressure cylinders.

Fire fighting should be done from an explosion-resistant location. Use water from

unmanned monitors or hoseholders to keep fire-exposed containers cool. If it is

necessary to stop the flow of gas, use water spray to protect personnel effecting

shut-off. Halon should not be used as an extinguishing agent on diborane fires.

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Pyrophoricity