Chronic Inflammatory Response Syndrome (CIRS) and mold-related illness arise from prolonged inhalation of mycotoxins, mold fragments, and other biotoxins in water-damaged or damp indoor environments. Occupants of buildings with active mold growth — particularly Stachybotrys chartarum (black mold), Aspergillus, and Penicillium species — inhale aerosolized mycotoxins that are absorbed systemically and accumulate in PBMCs. Conventional urine or serum testing frequently misses this intracellular burden. PBMC-based HRMS provides direct evidence of systemic mycotoxin absorption from inhalation, while EIS quantifies the resulting immune cell dysfunction. This combination is uniquely suited to objectively confirm WDB exposure in patients with unexplained multi-symptom illness, brain fog, fatigue, and immune dysregulation.