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Typical pollution sources in indoor air

  • People are the main source of carbon dioxide. CO2-levels are often used as an indication of the number of people and also the air quality in a room. Too high CO2-level can cause feelings of stuffiness and sleepiness but is hardly ever a real health problem. Indoor air level should not exceed 1000 ppm. CO2-levels can be reduced by improving air diffusion in the space and by increasing supply air volume.
     
  • Solvents, paints and other building materials as well as aerosol sprays and cleaning products may release volatile organic compounds (VOC) into air. Typical symptoms are allergic skin reactions and transient irritation of eyes and upper airways. Emissions are typically highest when materials are new. This is why effective ventilation is important, especially in new buildings, where it is recommended to run ventilation system 24/7. Otherwise VOC-sources e.g. damaged flooring material should be eliminated from the space.
     
  • Tobacco smoking is the biggest indoor air quality problem. This is why smoking is already prohibited in indoor spaces in many countries.
      
  • Cooking is a source of heat, grease and odours. Carbon monoxide (CO) and nitrogen dioxide (NO2) can be problem in spaces with defective gas appliances and combustion devices. Grease and heat must be exhausted locally and odours removed from exhaust air before air is extracted from building. Kitchen air can be improved using effective kitchen exhaust canopies as well as correct fresh air supply into space. At the same time it is important to make sure that exhaust ducts are free from grease in order to minimise fire hazards.
      
  • Human activities, like handling papers and clothes, generates room dust, which can irritate allergic people but there is no evidence of health effects among healthy population. However many impurities like viruses, bacteria, dust mites, mould spores, animal dander, and feathers can adhere to room dust. Dust from surfaces can be removed with good cleaning. Especially carpets need to be regularly maintained and cleaned with commercial floor cleaning equipment. This should be done so that any dust in indoor air can settle before the room is occupied.
      
  • Mineral wool and glass wool is frequently used as thermal and sound insulation material. This is why typical sources of fibres in indoor air are unprotected mineral and glass wool surfaces in ventilation system and damaged sound absorption panels in the ceiling. Man-made mineral and glass wool fibres of diameters greater than 3 µm can cause transient irritation and inflammation of the skin (itching), eyes and upper airways. However epidemiologic studies provide no evidence of permanent health effects. Problem can be removed by protecting all open wool surfaces or changing damaged panels.
      
  • Moisture damages can create serious indoor air quality problems. Growth of mould starts in wet structures. Often moist and earthy smell is a sign of moisture damage in the space. Typical health symptoms are irritation and inflammation of the skin (flushed facial skin burning), eyes and upper airways (runny nose, rhinitis) as well as fever. Refurbishment of moisture damages must be made carefully and all damaged building materials need to be removed. After that all surfaces and also e.g. garnish mouldings need to be cleaned thoroughly (first dry sweeping and then wet) . Make also sure that rainwater or snow cannot get inside your air-handling unit, where it can moisten air filters and insulation materials and create overflows. As important is to prevent water to get inside building structures.
      
  • Condensation collection drains and pipes of terminal units, cooling coils in AHU as well as cooling towers and decorative fountains need to be cleaned and possible blocks opened regularly. Otherwise there is a risk that air born Legionella bacteria starts to grow (20-45 OC, RH 65%) and ventilation or water distribution system distributes bacteria around the building. Recent research provides evidence that Legionella pneumophila, the causative agent of Legionnaires disease, can travel at least 6 km from its source by airborne spread. Typical symptoms are fever, chills, headache, muscle pain, low appetite, fatigue. and a dry cough. When there is a reason to suspect Legionella, it is important to remove the source and disinfect air conditioning ducts, humidifiers, shower heads, and any piping in which water can lay.
      

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