Mustard gas is a type of gas that was used as a chemical weapon in World War I. It is a yellow-green color and has a strong odor. Leaded gas is a type of gasoline that contains lead additives, which were commonly used in the past to increase octane levels. However, due to its toxicity, it is no longer used in most countries. NOBLE gases are a group of elements that are found in the atmosphere and are generally unreactive. TEAR gas is a type of gas that is used to disperse crowds or as a chemical weapon. It causes irritation to the eyes, nose, and throat. INERT gas is a type of gas that does not react with other substances and is used in a variety of applications, such as welding and fire suppression.