Screens are used that have a fine mesh - they can be used for air purification and filtration.
In areas where the air is relatively clean, screens with a mesh of perhaps .5 mm - 1 mm may be sufficient and standard for windows on houses.
for crawl spaces under buildings, a smaller mesh may be desired as to not let dust in.
There is also many types of plants that can be used indoors to improve of the air quality.W [1] [2] [3]