Breathing is vital to us. We cannot survive without proper breathing even for a few minutes. Although breathable air seems to be available everywhere, the air that we breathe everyday may contain some harmful contaminants that have various short-term and long-term effects to our health. This course introduces the possible sources of some commonly found indoor and outdoor airborne contaminants (e.g. formaldehyde, particulate matter, sulphur oxides, nitrogen oxides, carbon dioxide and volatile organic compounds) and their health effects, methods for monitoring the levels of these contaminants and the corresponding legislation for control. The course includes two laboratory sessions which allow students to acquire practical experience on measuring airborne contaminants using different types of devices.