Interpretation – Activity Levels
The activity level of a particular environment at the time of sampling will likely affect the data collected by that sampling. Indoor spore levels usually average 30 to 80% of the outdoor spore level at the time of sampling, with the same general distribution of spore types. Filtered air, air-conditioned air, or air remote from outside sources may average 5 to 15% of the outside air at the time of sampling. These percentages are guidelines, only. The major factor is the accessibility of outdoor air. A residence with open doors and windows with heavy foot traffic may average 95% of the outdoor level while high rise office buildings with little air exchange may average 2%. In addition, dusty interiors may exceed 100% of the outdoors to some degree, but will still mirror the outdoor distribution of spore types.
Utilizing aggressive or semi-aggressive sampling methods typically increases the number of spores on sampling media. While this may help to provide an indication of past problems with mold growth by agitating reservoirs of indoor spores, aggressive sampling compounds problems with interpretation because the comparison between an aggressively taken sample and the outdoor air is less meaningful.