Heating and Cooling Systems
For any closed cooling or heating system where the heat exchange fluid is completely contained within the system, corrosion of pipes and metal surfaces can be a serious problem. For systems that have steel pipes, sodium nitrite is commonly used as an additive.
It forms a protective film of iron oxide on the metal surfaces.
Odor Control for Wastewater
Sodium nitrite has other uses in water treatment. The Johnstown, Pennsylvania Wastewater Treatment Plant had a chronic hydrogen sulfide odor problem.
It was found that the addition of a blend of sodium nitrite and sodium nitrate to the waste sludge has produced a tenfold decrease in hydrogen sulfide and made working conditions more comfortable.
As with many chemicals, sodium nitrite is toxic in concentrated form. It is a strong oxidizing agent with a risk of fire or explosion in contact with other materials.
It can be harmful if swallowed, inhaled, or absorbed through the skin, and can cause irritation to eyes, skin, and the respiratory tract. For this reason, care must be taken when handling the substance.