Formalin
Formalin is a 35–40% aqueous solution of formaldehyde. When formalin acts on a bacterial cell, it causes denaturation (coagulation) of the cell's proteins. In a 5% formalin solution, spore forms die within 30 minutes; in a 2% solution – after 60 minutes; and in a 1% solution – after 2 hours. For disinfection, formalin is used as a 2% solution for treating the walls and ceilings of industrial premises. If mold is present, treatment should be carried out 2–3 times per month. Additionally, it is used for air disinfection in industrial premises. Spraying of the premises is recommended to be done after work, in order to The smell has already dissipated. For 1 cubic meter of space, 25 ml of formaldehyde is required. The room temperature should be no lower than 17-18 °C. With increasing temperature, the bactericidal effect of formaldehyde increases. Exposure time - not less than 5 hours. Food products must be removed from the disinfection area. After completing the disinfection, the air in the rooms is neutralized with a 20% ammonium chloride solution (15 ml per 1 cubic meter) for several hours. A drawback of formaldehyde is its toxic effect on human mucous membranes
Source: "Sanitary Regulations for Enterprises in the Margarine Industry" (approved by the Chief State sanitary physician of the USSR December 30, 1971 #946-A-71