Saltpeter: What you should know about the health risks

Saltpetre is the potassium salt of nitric acid and is therefore referred to in chemistry as potassium nitrate (KNO3). This salt damages building materials, causing plaster to flake off and forming white crystals.

• Saltpetre itself is not dangerous. The sodium salt is even used in the food industry for curing and as a fertilizer or in some toothpastes. But it is a clear indicator of moisture in the wall.
• Although saltpetre looks similar to mold, it is not a mold fungus. Salt crystals form here, which crumble easily when touched. However, these are not soft mold spores that can often be wiped away.
• But: Where saltpeter forms, mold is often not far away. This is because mold also likes to settle in damp walls. In addition, the salt promotes mold growth. This can pose a health hazard.
• Efflorescence is particularly common in houses near agricultural land. The salts are formed by the reaction of lime with already oxidized organic substances such as urine.
• Another, more long-term danger: saltpetre makes the building fabric unstable. In cases of extreme infestation, often caused by other salts as well, there is a risk of collapse. Saltpetre should therefore be removed from infested walls by a professional.