Each day a surface as large as a tennis court is exposed to a volume of air and contaminants that would fill a swimming pool1. Inhaled particulates pass through the nasal cavity where it encounters several different obstacles. As particles move deeper into the respiratory system, inhaled particles that transverse these barriers continually are filtered down to a size of 1-5 micrometers. The nasal cavity begins the filtration process. It contains physical barriers that can filter particles down to 15 mircons. The first is vibrissae, which are hair cells that can ensnare over 95% of particles 15 micrometers or greater. Tactile stimulation of these hair cells can induce sneezing to forcefully expel foreign material. In addition, several irritant
