Air protection technologies generate massive amounts of solid wastes, including fly ash (FA). Zeolite synthesis from FA seems to be an effective method for FA utilization. In addition, fly ash zeolites (FAZs) could be used for sulfur dioxide (SO₂) adsorption. Since there is a lack of sufficient information about SO₂ uptake on FAZs, we investigated this phenomenon in detail. Two commercially available zeolites, 3A and SM-27, and two FAZs, one manufactured by the authors and the other obtained from Kimura Chemical Plants, were used for SO₂ adsorption tests. Our experiments confirmed that FAZs could be efficient SO₂ adsorbents. Observed SO₂–zero emission periods varied from 2-3 min for non-activated zeolites to 7-15 min for their thermally activated counterparts. The thermal activation of FAZs increased 2-3 times their SO₂ adsorption capacity, resulting in up to 38 mg of SO₂/g of zeolitic material.