Common Sources of Indoor Air Contaminants

  October 4, 2013

Indoor air quality can be negatively affected by airborne contaminants and excess moisture. There are some usual suspects when it comes time to investigate a potential source of harm to indoor air quality. These include:

Air-supply intakes. These can receive an inadequate air volume, are favorite roosting places for birds, and have the potential to introduce contaminated outdoor air.

Sub-roof or below-grade areas. These areas are subject to moist still air, which promotes mold growth. Crawl spaces where water can puddle unnoticed are a breeding ground for mold, pests and allergens that can cause respiratory illness.

Chemical storage areas. Cleaning chemicals, paints and other materials can evaporate and release toxic vapors and volatile organic compounds.

HVAC ducts. Water in ductwork from humidifiers in the winter and condensate in the summer can grow mold. Any time there is high temperature with no air circulation, mold can grow rapidly. Plus, mold can stick on substances that adhere to duct walls, loosen, then enter the air supply.

Another common culprit that's less in your face than mold growth is poor airflow. Diagnosing this problem will require using an air-balance multimeter, which measures individual air velocity, temperature, and pressure. A flow-hood kit saves time by taking multiple air-velocity readings simultaneously and converting them into average airflow rates.

Other tools can be used to provide a more refined analysis of the air to indentify specific particulates or gasses. These include:
  • thermal imagers, which detect moisture from roof leaks or piping leaks inside walls, often hidden from view. Wet surfaces are colder than dry areas. The imager detects this temperature differential through building materials
  • a hot wire detector, which uses thermal conductivity to measure concentrations of inorganic gases
  • a flame ionization detector, which measures concentrations of aliphatic and aromatic hydrocarbons
  • an electron capture detector, which detects chlorinated hydrocarbons
  • a flame photometric detector, which measures concentrations of sulfur and phosphorus compounds
  • a mass selective detector, which measures the volume of IAQ pollutants and can identify unknown chemicals.


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