I think densities of mites in soil are typically in the range 10^3 to 10^5 per square meter. For example, see the Brady (1974) and Curl and Truelove (1986) numbers here.
In 2016, I used my microscope camera to look for dust mites around my own house during the summer, and I mainly only found them in areas with lots of accumulated skin flakes. Even in the flake patches, they didn’t seem dramatically more densely concentrated than the mites I filmed in the soil outside my house. Of course, this is just one data point. (Also, maybe I could only see the biggest ones? But that would apply to both indoor and outdoor mites.)
I think densities of mites in soil are typically in the range 10^3 to 10^5 per square meter. For example, see the Brady (1974) and Curl and Truelove (1986) numbers here.
In 2016, I used my microscope camera to look for dust mites around my own house during the summer, and I mainly only found them in areas with lots of accumulated skin flakes. Even in the flake patches, they didn’t seem dramatically more densely concentrated than the mites I filmed in the soil outside my house. Of course, this is just one data point. (Also, maybe I could only see the biggest ones? But that would apply to both indoor and outdoor mites.)