Usually, mold spores are concentrated closer to the ground, they spread with drafts. That's why never put mushroom fruiting chamber (monotub, growbox, shoebox etc.) on the floor, place it on some podium.
Now let's Imagine 2 people growing mushrooms in monotubs.
One guy bragging about zero contamination despite that tub is on the floor.
Another guy is begging for healthy harvest without contamination though follows all sterility recommendations.
Why? Every space has it's own contamination palette. It differs from corner to corner, among the rooms, between apartments and regions.
You can easily check your workspace with a simple test for mold. Do it yourself using agar. It's interesting and really cheap.
Enjoy your home mycology!