As a result of modern lifestyle, people spend 90% of their time in indoor environments and this is why, each day, sustaining acceptable indoor air quality (IAQ) becomes more important.
The indoor environment of any building is the result of the interaction of its localization, climate, HVAC systems (original design and modifications), contamination sources (building materials, furniture, equipments, activities, indoor activities and process and exterior sources) and building occupants. The Environmental Protection Agency has included IAQ among the top five environmental risks to public health.
We define Indoor Air Quality as the effect that contaminants that are generated or trapped in the building indoor environment have on the health and well-being (comfort) of its occupants. The term "indoor air" is usually applied to non-industrial indoor environments such as office buildings, public buildings (school, hospitals, theaters, restaurants, etc.) and individual homes.
We must point out that recent studies attribute 15 % labor absenteeism to respiratory conditions. Natural composition of air is 21% oxygen, 78% nitrogen and other traces of gases as 0.96% argon and 0.04% carbon dioxide, helium and water.
Technically we define an acceptable IAQ an air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction. This definition is used by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) in their standard 62.1-2007. Or, in simpler terms, an air that people perceives as fresh, comfortable, with no irritants or stuffy effect and that when inhaled will not represent any health risk.
Let us remember that we breathe approximately 3,600 liters of air a day in about 23,000 inhalations and in this intake of air we introduce to our body 5 million particles per minute (7,200 millions of particles a day).
Basically everything we find in an indoor environment can become a source of contaminants, releasing particulate (dust) or gases, or supporting microbial growth (mold or bacteria). Office equipment, such as photocopiers or laser printers, produces gases (ozone); curtains and furniture release fibers (particulate); inadequate cleaning, pest control and maintenance practices, result in an increase in airborne particles and gases; cosmetics, deodorants, and perfumes of the occupants, releases organic volatile compounds. Possibly the occupants are the mayor producers or contributors of contaminants, as human beings naturally produce carbon dioxide (CO2These contaminants can be classified in three main groups, which are: gases or vapors, particulate, and biological. Among the gases we can mention carbon monoxide, product of the combustion of vehicles (underground parking garages, loading zones, etc.), volatile organic compounds (VOCs) generated by glue (adhesives), inks, and plastic materials used in the manufacturing of furniture and other materials. How can we describe the smell of volatile organic compounds? When we are inside a new car, we say, "Hmmmm, it has a new car smell," this smell is the gases that are emitted.) and water vapor (respiration and transpiration), particulate (skin flakes) and biological aerosols.
