Mechanical ventilation of buildings is a risk factor for building related symptoms (BRS). Thisanalysis examines air filters within mechanical ventilation systems to determine their effect on BRS. Wehypothesize that certain ventilation filter materials will contribute more than others to the burden ofbuilding related headaches, mucous membrane (MM) and lower respiratory (LR) BRS within a building.This hypothesis was tested using the USEPA Building Assessment, Survey and Evaluation (BASE) study.Logistic regression models constructed to control for personal, workplace, and environmental factorsreveled statistically significant (p<0.05) associations between the increased prevalence of building relatedheadaches, certain MM and LR BRS and polyester or synthetic containing air filters in a ventilationsystem, relative to fiberglass or cotton air filters.