Toxic gases are those gaseous substances which can cause harm to the health of living organisms especially animals and humans. These gases can lead to short term or long-term health effects as well as death depending upon the concentration of gas, duration of exposure, and properties of the gas. They can cause adverse health effects such as irritation to eyes, nose and throat, respiratory problems, headache, nausea, dizziness, fatigue and even death. Common examples of toxic gases include carbon monoxide, sulphur dioxide, nitrogen oxides, ozone and hydrogen sulphide.