Which statement best defines a pyrophoric material?

Which statement best defines a pyrophoric material?

• A. Ignites within 5 minutes after contact with air.
• B. Releases toxic gas when heated.
• C. Remains inert in air.
• D. Forms an explosive mixture with air.

Answer: (A)

Pyrophoric materials ignite spontaneously when exposed to air because they react rapidly with oxygen, releasing heat that starts combustion without an external flame or spark. This immediate, self-igniting behavior is what defines pyrophoric substances. Saying they ignite within a short time after contact with air captures that spontaneous ignition characteristic, which is the key distinguishing feature. The other scenarios describe different hazards. Releasing toxic gas when heated is a toxic-decomposition hazard, not pyrophoric ignition. Remaining inert in air is the opposite of pyrophoric behavior. Forming an explosive mixture with air describes a different kind of reactivity that doesn’t require air exposure to ignite, whereas pyrophoric materials ignite on contact with air itself. In practice, handle pyrophoric materials under inert conditions and with appropriate safeguards to prevent exposure to air.

Pyrophoric materials ignite spontaneously when exposed to air because they react rapidly with oxygen, releasing heat that starts combustion without an external flame or spark. This immediate, self-igniting behavior is what defines pyrophoric substances. Saying they ignite within a short time after contact with air captures that spontaneous ignition characteristic, which is the key distinguishing feature.

The other scenarios describe different hazards. Releasing toxic gas when heated is a toxic-decomposition hazard, not pyrophoric ignition. Remaining inert in air is the opposite of pyrophoric behavior. Forming an explosive mixture with air describes a different kind of reactivity that doesn’t require air exposure to ignite, whereas pyrophoric materials ignite on contact with air itself. In practice, handle pyrophoric materials under inert conditions and with appropriate safeguards to prevent exposure to air.