Dalton's LawAs we think about the rules we inadvertently follow every day without even realizing it, such as speed limits and seat belt use, respiratory therapists need to remember that there are gas laws that we follow every day without even realizing this. This article will focus on a gas law called Dalton's law of partial pressures. In order for respiratory therapists to fully understand the importance of Dalton's Law, we must explain what this law states, how it applies to respiratory care, and what technological advances have been made to change the use of this law. In the early 1800s, a scientist by the name of John Dalton developed a theory that we now call Dalton's law of partial pressure. John Dalton developed this law by experimenting with gases in the atmosphere. “Dalton's experiments on gases led to the discovery that the total pressure of a mixture of gases amounted to the sum of the partial pressures that each individual gas exerted while occupying the same space” (A+E Networks, 2013). Mathematically, Dalton explained this law by stating that Ptotal= P1+P2+P3……Pn. These preliminary experiments performed by Dalton were based on the original 760 torr or 760 mmHg that had previously been discovered by Torricelli. Dalton then realized that the 760 mmHg in the atmosphere is made up of gases such as oxygen, nitrogen, carbon dioxide and some other trace gases. The pressure given off by each of these gases is considered the partial pressure of the total atmospheric pressure. The percentages of these gases in the atmosphere at sea level are nitrogen 78.08%, oxygen 20.95%, carbon dioxide 0.03% and remaining trace gases 0.94% which make up a total of 100% in the atmosphere . Considering Dalton's law partial pressures...... middle of paper...... partial pressures. After many years of development, we now widely use oxygen therapy to treat individuals with altitude sickness, and we can use hyperbaric oxygen therapy to treat divers with decompression sickness. As respiratory therapists, we owe the success of these two treatments to a scientist named John Dalton for developing Dalton's law of partial pressures. AE Networks. (2013). Biography of John Dalton. Retrieved from http://www.biography.com/people/john-dalton-9265201?page=1 Harvard Health Publications. (2013). Decompression sickness. Retrieved from http://www.drugs.com/health-guide/decompression-sickness.html Pendleton, L. D. (1999, November 07). When humans fly high: What pilots should know about high-altitude physiology, hypoxia, and rapid decompression. Retrieved from http://www.avweb.com/news/aeromed/181893-1.html?redirected=1