Joined: 05/12/2023 11:56 AM EDT
Location: Indiana, SW Michigan
Here is a great outdoor allergy and pollen interactive map.
On the tests you perform it is likely you will see spores into the 10 thousands on your outside control sample during warmer months. This is because spring and summer bring heat, humidity and rain when seeds fly through the air and grow on decaying leaves, compost piles and grasses causing mold spore counts to spike dramatically. In winter, counts can be zero in many places across the U.S. because growth is dormant.
You must take an outdoor control sample to compare what's happening on the inside of the house compared to outside. If levels are more inside than outside, you have a problem.
Note: It is not necessary to take an outdoor control sample if the winter weather outside is below freezing. While you can save a few bucks on lab analysis skipping it, sometimes it's not worth the argument over why you didn't include an outdoor control sample. Happy sneezing!