Outdoor air samplingYou have to be very careful about how much value you place on the outdoor sample when it's very low. The type of mold, the weather conditions and the time of year are significant factors which make it difficult to get an accurate outdoor assessment. Wet weather increases certain types of mold spores, dry weather does the opposite. Cold or snow can also decrease the outdoor count. You can also get low spore counts for several days after a big rain, then the counts will suddenly shoot up as the mold begins to thrive and becomes airborne.
What is more important is to look at the overall indoor spore count and the individual types of mold. Obviously, higher spore counts for common molds like the aspergillus or penicillium genera are less important than spore counts for stachybotrys, which would indicate a very wet environment somewhere in the house, perhaps hidden within walls. When you can't get a reasonably accurate outdoor count, you have to look at the total spore concentration. If there is no visible mold evidence and the home is dry, you can generally clear a job if the total concentration is below 10,000 per cubic meter and you are not looking at toxic mold.