What is a safe level of mold in air?

There are no definitive guidelines for mold spore levels in the air, so it is impossible to determine what level is safe and what level is unsafe. It is safe to say that the level that will affect one person will be different for another. In general, mold professionals rely on the outdoor mold spore concentrations to define what is “normal”, and those levels can change very rapidly. In the indoor environment, we expect the air to be reflective of normal outside fungal ecology.