Sulfur dioxide

Colourless toxic gas with a pungent, irritating, and rotten smell.

Toxic when inhaled.
Approximately two times heavier than air (density rate 2,2:1).

SO2 is used in food industry and winemaking as a preservative (E220) and in chemical industry (mainly as precursor to sulfuric acid). Due to its reducing properties, it may be used as bleachind agent for delicate materials.

Permissible exposure limit (OSHA PEL):

5 ppm (13 mg/m3) 15 min STEL

2 ppm (5 mg/m3) 8h TWA