Mold is a type of fungus present everywhere, including in the air.
Generally, normal amounts of mold in the environment pose no substantial health risk to healthy people with regular immune systems. However, some people are more susceptible to mold spores than others, and they may develop health problems after inhaling even a small number of spores. Therefore, mold should be thoroughly removed as soon as possible, and steps should be taken by a professional to prevent it from growing back.
Please note that different types of mold can affect different types of people at different times of the year.