Many different materials burn in the presence of oxygen. In most cases, the oxygen in the atmosphere is enough to facilitate combustion, but is often concentrated to enhance burning processes. Welders mix oxygen with propane and acetylene to increase the heat of their torches. The paper and petroleum industries also use oxygen to speed up their manufacturing processes where oxygen enrichment is necessary.
Oxygen is important for saving lives in every hospital. Patients with lung conditions rely on oxygen tanks and larger hospitals keep oxygen in bulk tanks. Smaller tanks are available for personal use. Oxygen is also used in emergency situations.
Similar to its application in combustion processes, liquid oxygen is the preferred oxidizer in space rockets. Current, as well as past, generations of space vehicles have all used liquid oxygen as an oxidizer and it is normally combined with kerosene or hydrogen to create large amounts of thrust. Most rockets have two chambers. One stores the oxygen and another hydrogen or another fuel. During launch, they are combined through a nozzle and ignited to produce thrust.
Scuba divers, firefighters and other professionals in hazardous environments that prevent breathing air rely on liquid oxygen stored in tanks to keep them alive. As anyone who has flown commercially knows, planes are equipped with emergency oxygen masks that can drop down from the ceiling if the cabin loses pressure.