There are a number of ways to monitor the air for bioaerosols which includes impaction, filtration and surface sampling. A passive method used to determine the types of viable microorganisms in a given area is settle plate which involves only exposing a dish filled with nutrients to the air. Active and cost effective methods collect samples using a pump that draws air across a nutrient dish (MAS 100). If a dish of nutrients is used it can be incubated directly to quantify viable microorganisms in the air and identify the types using microscopy and other techniques (e.g PCR). As with other methods, the results of the air sampling methods alone cannot eliminate the possibility that contamination exists because different varieties of microorganisms favor different methods of sampling and analysis. Another reason that an air sample may not completely represent the microorganisms that are present in a building is that sampling may have been performed during a time when the mould was inactive. Therefore follow up sampling for airborne microorganisms is also very important