PFAS sampling is different from other types of sampling because PFAS are present in many things we use in our everyday life, such as water-resistant and stain-resistant products. PFAS compounds are detected in very small quantities (parts per trillion).
To put this in context, 1 part per trillion is equivalent to a single drop of water in 20 Olympic-sized swimming pools combined. Even the smallest cross-contamination could contribute to a false positive sample.