Toluene is readily absorbed from the lungs, and most exposures to toluene occur by inhalation. Toluene’s odor is discernable at a concentration of 8 ppm, which is 25 times less than the OSHA PEL (200 ppm); therefore, odor generally provides adequate warning of acutely hazardous concentrations. Its vapor is heavier than air and may cause asphyxiation in enclosed, poorly ventilated, or low-lying areas.