For over a century, researchers have been concerned with what testing protocols to assess indoor fungi growth were most reliable. To that end, various sampling and analysis methods were developed. However, to present no testing procedure has been standardised. The vast number of different fungi species, the differences in their biological properties and their implications on the occupants’health and building fabric can make the decision-making process for an appropriate assessment protocol challenging. This research aims to make a critical review of passive (or nonactivated) and active (or activated) sampling and emphasize potential errors while interpreting results obtained from passive or active protocols.