FAI is an innovative assessment concept based on air sampling that can provide information on:
• Presence of a fungal source
• Potential exposure to fungi
• Potential exposure to total allergens
• Room cleanliness
What is the Fungal to Allergen Index?
The FAI concept is a tool developed to assist the visual (and odour) assessment that is the core of all fungal growth inspections. It is based on experimental data from normal buildings with no visual or other signs of water damage or fungal problems. Data from these buildings showed that the median FAI index (the percentage of the total allergens that originate from fungi) was 8%. In buildings with known problems (water damage or fungal growth) the FAI values were ranging between 40-99%.
Based on these findings it is easy to see that the FAI values can be used to predict sources of fungal growth.
In addition, it also provides information on the actual levels of both fungi and total allergens (dust mites, pollen, fungi, dander and other).
How is it performed?
Parallel air samples are analysed for total fungi and for total allergens. The dual samples give information on both the potential exposure to fungi and to total allergens (dust mites, pollen, fungi, pet dander, etc.). The core of the FAI concept is to calculate the ratio between total fungi and total allergens, to predict the presence of a fungal source. Results can be obtained in 1 to 2 hours and are objective data, independent of the subjectivity of microscopy.
FAI is an alternative to the traditional concepts of evaluating presence of water damage fungi versus normal dust flora fungi, or looking at differences between the fungal population of indoor and outdoor samples. FAI is also an alternative to the DNA based methods such as ERMI, which is an algorithm based on the traditional assumption of certain fungal species being water damage fungi and other species being normal dust fungi.
More reproducible and representative air sampling
At the 2020 IAQA conference, a technical presentation showed that activated air sampling (resuspension of settled fungal particles) gives more reproducible and representative results. Also, activated sampling, allows characterization of space conditions independent of prior activity in the room.
Reproducibility is critical to being able to reliably interpret the data.
How is it possible to make interpretation criteria?
Despite being used for decades, no clear interpretation criteria exist for the traditional air sampling using cultivation or spore traps. Use of many different types of equipment, different sampling protocols, subjective interpretation of the samples (microscopy) has rendered interpretation criteria impossible. Variability can occur during sampling and during analysis. ASTM D7391* documented that spore trap analysis has a RSD of 25-200%. There are peer reviewed published papers that document the variability of passive spore trap sampling as high as 500%. The most significant factor influencing variability is the almost universal use of non-activated sampling. If data are not reproducible, interpretation criteria cannot be established.
According to the verification report performed by US-EPA (2011) the Mycometer air test is highly reproducible. It is mandatory to use the sampling protocol developed by Mycometer, securing that all Mycometer air users, are sampling the same way, using similar equipment. Sampling is performed using a membrane filter shown to have very high and constant collection efficiency. The biochemical analysis is objective and independent of who is performing it. However, even with this technology, interpretation criteria are, for most applications, only possible because activated sampling has been used.
How to interpret results?
Below are some examples of what FAI results can look like and their interpretive value.
Example 1: Bedroom
The Mycometer air value (MAV) for the fungi is 607 FLU per m³ of air. The number is high (category C) compared to the population found in buildings with no visual signs (or smells) of fungal growth or water damage (Data was presented at the IAQA conference 2021). The MAV for allergens is 17780, which is also very high. However, the FAI is 3% which is quite low.
FAI is calculated as , or in this case
The interpretation is that there is a risk of potential exposure to a high level of both fungi and of total allergens. Even though fungi and allergens are high, the FAI value is very low indicating that there is no mould source but rather a poor cleaning standard is the cause.
Example 2: Three rooms with high FAI but very different levels of both fungi and allergens
The high FAI results for three rooms presented below strongly indicate the presence of a fungal source in, or in the vicinity of, the rooms. Notice, however, the high difference in the fungal level, ranging from 186 to 3107. This demonstrates that the quantification of fungi alone is not necessarily a good indicator of the presence of a fungal source.
The potential exposure to fungi is almost 17 times higher in the kitchen than in living room 2.
Example 3: Three rooms with low to normal FAI
FAI indicates it is unlikely that there is a fungal source in or in the vicinity of, the room, that contributes significantly to the level of fungal particles (spores and hyphal fragments) into the room. Again, even though the level of mould is 20 times higher in the bedroom than in the bathroom the conclusion is the same. This variation can be explained by a difference in the cleaning standard (measured as the variation in the total allergen level). The level is 36 times higher in the bedroom compared to the bathroom.