Estelle Levetin, PhD University of Tulsa Fungal spores, commonly called mold spores, are a normal component of the outdoor air. They are present in the atmosphere anytime that the ground is not covered with ice or snow. Many species of fungi are found as leaf surface microorganisms where they exist on organic matter produced by the plant.
Concentrations outdoors can be high, especially in the late summer or fall.
We have occasionally recorded hourly concentrations in Tulsa above 100,000 spores per cubic meter of air. Actually the outdoor air may be the source of the spores whenever fresh air is introduced. In addition, many indoor locations may serve as amplification sites for the growth of fungi. Such sites include carpeting, upholstered furniture, showers, shower curtains, other bathroom fixtures, potted plants, and the soil around potted plants. Anytime moisture or even high humidity is available, spores can germinate and fungi can grow and produce thousands of new spores utilizing organic material in these sites.