Black Spots on Floor Tiles
Approach: An affected floor tile was submitted to determine if the previous mold testing had missed a source on the tile backing or mastic. Additionally, a new tile from the same manufacturing lot was submitted for comparison. The process of preparing and examining the sample and reference tile was documented. Areas with darkened surface features were imaged and then cut out and examined.
Scanning electron microscopy with energy dispersive xray spectroscopy (SEM-EDS) was used to identify the particles. The SEM showed an elevated concentration of iron and iron oxide in the impacted areas. The backscatter electron (BSE) image which correlates brightness in the image with atomic density, highlighted the iron particles that were embedded in the tile and the EDS spectrum confirms the PLM Image chemical composition of these higher density particles.
Also, the color EDS map highlights the iron particles in the mineral filled PVC floor. These iron particles were concentrated in areas were the tile showed signs of impact which indicated some metallic object impacted the tile leaving behind small particles and over time the materials oxidized which created darker spots in the tile.