LCS Laboratory tested 100s of samples of construction materials collected from water-damaged buildings. The statistical analysis of the data reveals what is typical and what should be treated as elevated mould growth.
The samples were delivered to the lab by the general public, contractors, safety consultants, and insurance assessors. 99% of the samples were collected in SW Ontario and are random in terms of the season, nature of the construction material, and client’s expertise. While the origin of the samples is unknown to the laboratory, it is likely that the samples were collected from water-damaged or mold-contaminated buildings.
LCS Laboratory tested surface contamination of the construction materials with mold spores using Pase Contrast Microscopy or Staining Microscopy at magnification 400. The most common types of mold were identified and their concentration is measured in units of spores per mm2 (sp/mm2). We report the following spores:
Alternaria
Ascospores
Aspergillus/Penicillium-like
Basidiospores
Chaetomium
Cladosporium
Curvularia
Drechslera/Bipolaris-like
Smuts/Myxomycetes/Periconia
Stachybotrys/Memnoniella
Ulocladium
Hyphal fragments
Miscellaneous/Unidentifiable
Our findings show that mold was detected on 95% of the samples. While the surface concentration wildly ranges from 3 sp/mm2 to as high as 300,000 sp/mm2 the median value is about 100 sp/mm2 . The distribution of the spore concentrations between samples can be approximated by the log-normal distribution with the following cut off points:
<10 sp/mm2 – 10% of the cleanest construction materials have less than
100 sp/mm2 – This is the median concentration. 50% of all tested samples had mold concentration below 100 sp/mm2
1000 sp/mm2 – 75% of all tested samples had shown mold concentration below 1000 sp/mm2
1000 sp/mm2 – Only 25% of the most contaminated samples had mold concentration above 1000 sp/mm2
The above-mentioned cut-off concentration can be used to intrepid the mold assessment results and findings. They provide a simple tool to otherwise qualitative microbiological results into quantitative analysis.
LCS Laboratory is a professional Safety, Industrial Hygiene, and Air Quality Laboratory. If you want to cut your cost and receive service from the industry leaders, please contact us for a free quote and the sampling instructions.
at 5:03 pm
Meanwhile …. ASTM requires reporting in fs/cm2 not. sp/mm2
In built houses we find most building products that have not been water damaged have a fungal structure concentration of <500fs/cm2
at 10:31 am
Hi Joseph, thank you for letting me know. Which ASTM method are you using? 500 fs/cm2 sounds like a lot of mold. At 1000 fs/cm2 you can see mold stains with the naked eye.