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 37oC.
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 19oC and 34oC.
| Dry bulb temperature (oC) | 10 | 14 | 18 | 22 | 26 | 30 | 34 |
|---|---|---|---|---|---|---|---|
| Sensible heat (W) | 135 | 112 | 100 | 95 | 84 | 59 | 29 |
| Latent heat (W) | 22 | 22 | 22 | 24 | 34 | 59 | 90 |
| Total heat (W) | 157 | 134 | 122 | 118 | 118 | 118 | 119 |
Related Topics
• Physiology
Human physiology, air quality and comfort temperatures, activity and metabolic rates, health effects of carbon monoxide and more.
Related Documents
Age and Physical Growth - Weight and Height
Age and typical physical growth of boys and girls - age 2 to 18 years.
Air Contaminants - Exposure Limits
Exposure limits for various air contaminants.
Ammonia - NH3 - Concentration in Air and Health Effects
Ammonia and health symptoms - smell and threat to life.
Body Weight vs. Body Height
Typical ideal body weight versus height.
Carbon Dioxide Concentration - Comfort Levels
CO2 acceptance and comfort level.
Carbon Dioxide Concentration in Rooms Occupied with People
Carbon dioxide concentration in a room may indicate air quality and ventilation system efficiency.
Carbon Monoxide and Health Effects
Exposure to Carbon Monoxide - CO and health effects.
Emissions from the Human Body
Gaseous polutants emissions from human bodies.
Human Body - Specific Heat
Specific heat of the human body - compared to substances like protein and wood.
Human Body Composition
Composition of the human body.
Human Heat Gain
Heat gain from persons in air conditioned spaces - in btu/hr.
Humans - Required Rest Time
Relaxation rest time vs. working time and activity.
Life Expectancy
Age and life expectancy for men and women.
Met - Metabolic Rate
Metabiolic Rate - Met - is used as a measuring unit for human body heat or power production.
Outdoor Makeup Air
Acceptable indoor air quality and required make up air.
pH in Human Biological Material
pH in human materials like blood, salvia and more.
Physiology - Activity and Metabolic Rate
Heat production from the human body vs. activity.
Recommended Relative Humidity
Recommended relative humidity level.
Required Space per Person
Room area per person - may be used to calculate typical indoor climate loads.
