The act of drawing of air or other substances (fumes, mists, vapor, dustetc). into the lungs (the respiratory system). An easier definition is "breathing in". The act of inhaling and exhaling is called respiration or, more simply, "breathing". Additional Info: Inhalation of hazardous materials affects the body in two ways. First, there can be irritation, allergic reaction or other damage to the lungs, respiratory tract, and/or mucous membranes. Second, the foreign substance may be absorbed into the bloodstream in the lungs and then distributed through the body. Avoid inhaling anything other than clean air. Even if a substance is not listed as hazardous, inhaling dusts etc. can irritate the lungs. Chronic (long-term) inhalation of such substances can lead to permanent damage including bronchitis, emphysema or pneumoconiosis. Even inhalation of sea water can lead to life-threatening acute respiratory distress syndrome (ARDS). And, of course, tobacco products kill. Always remember to use appropriate engineering controls such as fume hoods and proper ventilation when planning work in which hazardous materials could be inhaled. If these means are not sufficient, be sure to use appropriate personal protective equipment (PPE) such as an appropriately-selected respirator. MSDS Relevance: Inhalation is one of the four routes of entry often discussed on an MSDS (the other three are ingestion, absorption, and injection. The MSDS will describe the symptoms of inhalation exposure as well as the engineering controls, personal protective equipment, and other measures that can be taken to reduce the risk of the inhalation hazard. See also: Bronchitis, Edema, Respirator, Smoke