Abstract: A process for deodorizing polluted air, wherein the air to be deodorized is washed in a washing apparatus with an aqueous solution of hydrogen peroxide. The solution is circulated in a closed circuit while ozone is introduced either directly into the air to be treated or directly into the aqueous solution which is thus regenerated. The initial weight percentage of hydrogen peroxide in the aqueous solution is within the range of 0.5% to 10%.

Abstract: A process for purifying gaseous effluents containing aldehydes comprises submitting the gaseous effluents to the simultaneous action of SO.sub.2 and NH.sub.3 followed by washing with water. The ratio of the required quantities of NH.sub.3 and SO.sub.2 is between 2:1 and 3:1.When the gas to be purified naturally contains NH.sub.3, as is for instance the case in rendering plants, the quantity of NH.sub.3 to be added to the gas is reduced accordingly. Conversely when the gas to be treated naturally contains SO.sub.2, the quantity of SO.sub.2 to be added to the gas is also reduced accordingly. The most favorable ratio would correspond to a pH of the washing waters of between 7 and 7.5.