People and students spend about half their waking hours at work or school. Therefore, maintaining adequate indoor air quality (IAQ) in schools and the workplace is becoming a top priority for facility managers and building operating engineers. An essential
element for maintaining adequate indoor air quality is outside air to dilute indoor air pollutants and exhaust these contaminants along with moisture and odors from our buildings. Why measure carbon dioxide?
Most heating, ventilation and air conditioning systems (HVAC) re-circulate a significant portion of the indoor air to maintain comfort and reduce energy costs associated with heating or cooling outside air. When occupants and building operators sense air coming
out of an air supply duct, it’s virtually impossible to judge how much of this air is simply re-circulated air and how much is outside air. Current technology allows easy and relatively inexpensive measurement of carbon dioxide ( CO2 ) as an indicator to help ensure ventilation systems (for high density occupancy zones) are delivering the recommended minimum quantities of outside air to the building’s occupants.
What is carbon dioxide?
Carbon dioxide is a natural component of air. The amount of CO2 in a given air sample is commonly expressed as parts per million (ppm). The outdoor air in most locations contains down to about 380 parts per million carbon dioxide. Higher outdoor CO2 concentrations can be found near vehicle traffic areas, industry and sources of combustion. Where indoor concentrations are elevated (compared to the outside air) the source is usually due to the building’s occupants. People exhale carbon dioxide—the average adult’s breath contains about 35,000 to 50,000 ppm of CO2 (100 times higher than outdoor air). Without adequate ventilation to dilute and remove the CO2 being continuously generated by the occupants, CO2 can accumulate.
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