Categories of contamination

The Mycometer®-test provides you with validated criteria for documenting and delineating the amount of fungal material on a surface.

The Mycometer®-values have been divided into three categories. These categories of surface contamination were developed as a result of testing performed in collaboration with the Danish Building Research Institute and the Technical University of Denmark.

101 samples from clean surfaces, with no visible dust or dirt, in well maintained buildings with no mold problems were analysed. All samples showed MV-values below 25. Therefore, MV-values below 25 are defined as the normal background level of mold. Samples having a MV-value of 25 or less are not sterile and low level of spores are likely to be present. This level of mold is characterized as Category A.

Levels of mold above this background level can be due to either accumulated spores, such as in dust or actual mold growth. However, the level of mold will almost always be substantially higher on surfaces with growth compared to surfaces with accumulated spores. This quantitative difference constitute the basis for the division in Category B  and Category C.

Samples were taken on surfaces with visible accumulation of dust or dirt varying from barely visible to very dirty, where not all dirt could be collected by the swab (n=127). The test results were described by a log normal distribution. About 96 % of the samples showed a MV-value of less than 450. Category B was defined as MV-values higher than 25 but lower than 450.

The signals obtained from surfaces with mold growth that are above 450 (samples with MV-values up to 40,000 MV have been registered) are termed Category C. Category C results means that the biomass density of mold is very high, a clear indication of mold growth.

Interpretation and detection limit