Definition - What does Gas mean?
A gas is a fundamental state of matter. Single element molecules (hydrogen) or compound molecules of different elements (carbon dioxide) form gas. A gas mixture may contain different gases such as air (nitrogen, oxygen, carbon dioxide) or natural gas (methane, ethane, propane, butane).
Unlike liquids and solids, gas molecules remain widely separated from each other and there is no inter-molecular attractive force. Gases are generally invisible or colorless as the density is low. Some elements remain at gaseous forms at normal temperature (e.g. 30 degree Celsius) such as hydrogen, oxygen, nitrogen.
Safeopedia explains Gas
Gases are used for many purposes such as lifesaving, fuel, production, welding cutting, freezing, transportation, preservation, chemical process, in chemical weapons. Some gases are safe for humans while others pose a harm to human health and properties. Others may be inert or hazardous under influence. Combustible gases may cause explosions or fires, and are, therefore, fire hazards. Toxic gases cause death or illness.
Workers working in a space with known gas related hazards should wear an appropriate respirator and clothing. People entering in a confined space must also take appropriate precautions against the presence of dangerous gases and explosions. Positive risk controlling is mandatory for entering such dangerous areas with known potential gas related to health risks. Risk controlling factors include: monitoring and controlling, isolation, warning signs, working procedures, training and awareness, clothing and PPE, medical support and emergency evacuation.