Poison gas refers to toxic chemical substances that can cause harm or death when inhaled. These gases can disrupt normal bodily functions, leading to respiratory failure, organ damage, or other serious health issues. Common examples include chlorine, mustard gas, and sarin. Poison gas has been used in warfare and can also be released accidentally in industrial settings. The use of poison gas in conflicts, particularly during World War I, raised significant ethical concerns and led to international treaties aimed at banning chemical weapons. Today, regulations exist to prevent the production and use of such harmful substances, promoting safety and public health.