The only way to know if there is mold and it is not visible is by getting an air quality test done. An air quality test or IAQ is a test where air samples are taken to determine what type or dust/mold spores are in the air. Once diagnosed, a report will be provided, which indicates the type of mold and levels.. There are a minimum of two tests that need to be done, one inside and one outside. If the levels inside are higher than the ones outside, then we know we have an issue.
Mold is not always visible so it is important to keep a lookout for any signs. Some signs are:
1. Musty/ Earthy Odour
2. Skin irritations
3. Cold like symptoms
4. Respiratory issues
5. a recent water damage / leak in which could result in mold growth
I hope this has helped!