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).

The average composition of exhaled air is

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^oC.

Heat loss from human body

The total heat loss from an adult at normal activity is approximately 118 W (2 Met) in at room with temperatures between 19^oC and 34^oC.

Dry bulb temperature (^oC) Load Calculator!	10	14	18	22	26	30	34
Sensible heat (W) Load Calculator!	135	112	100	95	84	59	29
Latent heat (W) Load Calculator!	22	22	22	24	34	59	90
Total heat (W) Load Calculator!	157	134	122	118	118	118	119

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Human Need of Air

Fresh air is required for respiration and for transport of heat and vapor emitted from the human body.

Respiration

Equilibrium of Heat

Heat loss from human body

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