Human Need of Air
Fresh air is required for respiration and for transport of heat and vapor emitted from the human body. This tool calculates heat loss from the human body at different dry bulb temperatures.
Human Need of Air
Fresh air is required for respiration and for transport of heat and vapor emitted from the human body.
Respiration
An adult at rest breathes 15 - 18 respiration per minute - exchanging 0.5 liter - approximately 0.5 m³/h. With harder work the rate is 3 to 6 times more (1.5 - 3 m³/h).
Average composition of exhaled air
- Oxygen: 16.5%
- Carbon dioxide: 4.0%
- Nitrogen and Argon: 79.5%
The quantity of carbon dioxide exhaled in 24 hrs is about 1 kg.
Equilibrium of Heat
Heat is generated within the human body by the combustion of food. The heat is lost from the body by:
- Conduction and convection: about 25%
- Radiation: about 43%
- Evaporation and moisture: about 30%
- Exhaled air: about 2%
Evaporation prevails at high ambient temperatures. Conduction and convection prevails at low ambient temperatures. Heat is liberated in a rate maintaining the internal body temperature at 37°C.