Sodium sulfite (Na₂SO₃) doesn't directly give off a gas under normal conditions. However, it can react with acids to produce sulfur dioxide (SO₂) gas, which is a colorless, pungent gas.

Here's the chemical equation for the reaction:

Na₂SO₃ (aq) + 2 HCl (aq) → 2 NaCl (aq) + H₂O (l) + SO₂ (g)

Important Note: Sulfur dioxide is a toxic gas and should be handled with care.