Given the increasing prevalence of energy efficient buildings with lower outdoor air exchange rates, passive removal materials (PRM) have become known as a potential strategy for reducing occupant exposure to indoor air pollutants without an energy penalty. In recent test chamber studies, wool has shown to be a potential PRM for removing formaldehyde. Formaldehyde measurements were taken before, during, and after wool curtains were hung behind the south façade, under the room’s diffusers. Experiment results by Daniel Lu found that formaldehyde levels correlated with indoor humidity levels, which appear to dominate any potential passive removal effect of the wool curtains. Future studies should isolate removal capabilities of the wool across the same indoor conditions. More importantly, cost benefit analyses should be conducted to evaluate how well PRMs can lower formaldehyde exposure compared to other exposure mitigation strategies.