Self-contained breathing apparatus pressure changes with ambient temperature. As temperature decreases, the pressure inside the cylinder decreases. The relationship between the temperature and the pressure of a gas is defined by the formula "PV" = "nRT". (See Universal gas constant.) What is particularly important to understand from the formula is that the temperature is in kelvins, not degrees Fahrenheit. Consider the freezing point of water at 32 °F (0 °C, 273.15 K) and compare it to 96 °F (35.6 °C or 308.71 K; normal human body temperature is 37 °C). While 96 is arithmetically three times 32, the difference in temperature from a
Temperature higher energy than at positive temperature, and may be said to be in fact hotter at negative temperatures. When brought into contact with a system at a positive temperature, energy will be transferred from the negative temperature regime to the positive temperature region. Temperature Temperature is a physical quantity expressing hot and cold. It is measured with a thermometer calibrated in one or more temperature scales. The most commonly used scales are the Celsius scale (formerly called "centigrade") (denoted °C), Fahrenheit scale (denoted °F), and Kelvin scale (denoted K). The kelvin (spelled with a lower-case k) is the unit of