How does sodium react with hydrogen gas at high temperatures?

When sodium reacts with hydrogen gas at high temperatures, it forms sodium hydride (NaH), a flammable crystalline compound.12

While pure sodium begins to absorb hydrogen at approximately 100 °C (212 °F), the rate of this absorption increases as the temperature rises. To produce pure sodium hydride, sodium is typically exposed to a high flow rate of hydrogen gas at temperatures exceeding 350 °C (660 °F). At even higher temperatures, the compound can undergo dissociation back into hydrogen and molten sodium.2