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Erschienen in:
2021 | OriginalPaper | Buchkapitel
Indoor Air Quality: Status and Standards
verfasst von : Freja Hasager, Joachim Dithmer Bjerregaard, James Bonomaully, Hasse Knap, Alireza Afshari, Matthew Stanley Johnson
Erschienen in: Air Pollution Sources, Statistics and Health Effects
Verlag: Springer US
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Excerpt
Aerosol
A suspension of particulate matter composed of solid and/or liquid material in a gas.
Carbon Dioxide (CO2)
CO2 is a part of the atmosphere (>405 ppm), and indoor concentrations in excess of ambient are mainly generated by people, about a kilogram per day depending on metabolism. The indoor exposure limit is commonly taken as 1000 ppm, a level at which the negative health effects of CO2 are not yet significant. CO2 is a useful proxy for general indoor air quality including bioeffluents. Continued exposure to CO2 levels over 2500 ppm have been linked to drowsiness and tiredness. Studies have shown impacts on decision making and focus from around 1300 ppm [1].
Carbon Monoxide (CO)
CO is a product of incomplete combustion. Indoor sources include heaters and stoves, tobacco smoke, and candles. CO is toxic to humans. Ambient air contains about 1 ppm of carbon monoxide. In busy streets, the atmospheric mole fraction can be in the range of 10–20 ppm. Indoor levels generally follow outdoor levels except in poorly ventilated houses with indoor CO sources [2].
Formaldehyde (CH2O)
CH2O is a volatile organic compound that is found in indoor air due to off-gassing from building materials containing adhesives and polymers and objects like furniture and fabrics. It is also formed from the oxidation of hydrocarbons; in the indoor environment, this includes cigarettes and ozonolysis of aromatic hydrocarbons. Indoor concentrations depend on the age of the building and vary depending on season and time of day. CH2O is known to cause adverse health effects in humans. According to the World Health Organization’s guideline for formaldehyde, exposure should not exceed 0.1 mg/m3 (30-min average) [3].
Ventilation Systems
Ventilation can be effectuated by mechanical or by natural means. In mechanical ventilation, fans are used to ventilate an enclosed space, while natural ventilation is dependent on the outside conditions and is driven by natural forces.
Because modern buildings are becoming more well sealed (more impenetrable), ventilation or air exchange rates between indoor and outdoor air have decreased. This improves thermal efficiency, but contaminants from indoor sources will be trapped inside resulting in elevated pollutant concentrations that can cause adverse health effects in the occupants. It is now recognized that an optimal balance between energy conservation and indoor air quality (IAQ) must be maintained to provide the occupants with a healthy indoor environment. CO2 can be used as general indicator of indoor air quality (IAQ) and ventilation rate, as low ventilation rates will cause the accumulation of CO2 as well as other pollutants. CO2 sensors are often used in demand controlled ventilation to control bioeffluents from humans. A stable level of 850 ppm of CO2 should be sufficient for a healthy indoor environment and could be provided by a ventilation rate of 10 l/s per person.
Particulate Matter (PM)
Particulate matter is a conglomeration of molecules in the liquid and/or solid phase occurring, together with gas, in an aerosol. PM is typically characterized according to mass and aerodynamic diameter. PM10 is defined as the total mass density (μg/m3) of all particulates with an aerodynamic diameter ≤ 10 μm, PM2.5 is a measure of all particulates with an aerodynamic diameter ≤ 2.5 μm, and ultrafine particles (UFP) are particles with an aerodynamic diameter ≤ 0.1 μm.
Primary and Secondary Pollutants
Primary pollutants are pollutants directly emitted from a source. Secondary pollutants are formed in situ from primary pollutants.
Sick Building Syndrome (SBS)
A situation in which people who spend time indoors feel unwell and suffer from symptoms including throat irritation, difficulty breathing, runny nose, sneezing, headache, dizziness, difficulty concentrating, and nausea. The severity of symptoms often increases with the amount of time spent in the building.
Technosphere
The technosphere is the part of the environment modified by technology and includes buildings, vehicles, and public infrastructure like the subway and highways. Humans spend the majority of their time in the technosphere.
Terpenes
A class of hydrocarbons of biological origin with a skeletal structure derived from isoprene. Of particular concern in the indoor environment are monoterpenes like pinene, limonene, linanool, and menthol, used as scents, e.g., in cleaning agents.
Ventilation Rate
The flow of outdoor air into a space resulting in removal or dilution of indoor air pollutants. Given in units of volume per time or air exchanges per hour.
Volatile Organic Compound (VOC)
Volatile organic compounds (VOCs) are organic chemicals that have a high vapor pressure (boiling point below 250 °C) at room temperature. There are many VOCs, both natural and man-made, including most scents and odors. Many VOCs are regulated by law due to their health impacts [4].