Volatile organic compounds (VOCs) are airborne carbon-based molecules produced by chemicals vaporizing at room temperature. VOCs come from a wide range of sources, such as cleaning and personal care products, building materials, surface coatings, and living organisms such as mold and human occupants. VOC formation can also result from indoor chemical reactions between other air compounds.

There are hundreds of different chemicals which are categorized as VOCs, for example, alcohols, aldehydes, ketones, organic acids, amines, organic chloramines, aliphatic and aromatic hydrocarbons.

Likewise, the indoor sources of VOCs are numerous, including:

  • paints and solvents
  • wood preservatives
  • aerosol sprays
  • cleansers and disinfectants
  • pesticides, moth repellents, and air fresheners
  • stored fuels and automotive products
  • dry-cleaned clothing
  • glues and adhesives, permanent markers, and photographic solutions
  • building materials and furnishings
  • copiers and printers

Given the large variety of compounds with the ability to be released as gases from solids or liquids, and therefore classified as VOCs, it is not surprising that the health effects vary — ranging from harmless to extremely toxic. The US Environmental Protection Agency's "Total Exposure Assessment Methodology Study" found levels of common VOCs pollutants to be two to five times higher inside homes compared to outdoors, regardless of whether the homes were in rural or highly industrial areas. While there is lack of clarity about what specific health effects occur from VOC levels usually found in homes, there is clear evidence from healthcare workers that exposure to surface cleaning and disinfecting products are associated with increases in asthma and respiratory symptoms.

The list of immediate symptoms and long-term illnesses associated with VOCs exposure is lengthy, and includes:

  • visual disorders and memory impairment
  • eye, nose, and throat irritation
  • shortness of breath, wheezing dyspnea
  • headaches, dizziness, loss of coordination, fatigue
  • damage to the liver, kidney, and central nervous system
  • allergic skin reactions
  • declines in serum cholinesterase levels
  • nausea, vomiting
  • fatigue
  • cancer in laboratory animals and potentially in humans

Measuring VOCs in Occupied Spaces

As a practical time and cost-effective method of measuring indoor air for contamination, total VOCs (tVOCs) are used as a surrogate approximation for the complex mixture of VOCs present simultaneously in the air. TVOC sensors measure ambient concentrations of a broad range of “reducing gases” associated with discomfort or health problems. In addition, real-time tVOC measurements can show short-duration averages and peak exposures that may reveal environmental triggers for asthma or other respiratory disease symptoms. Indoor air quality guidelines for tVOC levels have emerged globally with a maximum level from ~0.6 to ~1 mg/m3 considered acceptable.

There are two main types of sensors used to detect VOC levels in the air. Each sensor type is specially designed to monitor specific compounds in varying environments.

Metal oxide sensors (MOS) use a thin film to detect compounds in the surrounding atmosphere, such as benzene, ethanol, and toluene.

Photoionization detectors (PID) break down compounds into positive and negative ions using ultraviolet light to energize electrons in a molecule, eventually causing electrons to be ejected from the molecule which produces an electrical current which is detected by the device.

There are, however, drawbacks to these relatively affordable devices. For example, these sensors are calibrated to one known gas so the readings are only an approximation of the total and cannot identify the individual compounds in the air. Laboratory analysis of samples collected on sorbent tubes, passive badges, or in canisters is the most conclusive way to measure VOCs, but due to higher expense and slower turnaround time, this approach is often not feasible.

In summary, like other pollutants, the extent of the impact of airborne exposure to VOCs on occupant health depends on many confounding variables. These include the age, health, and activity level of the person in the space, the ability of the VOCs to cross physiological barriers, and the level and length of time of exposure. It is clear, nonetheless, that both short- and long-term exposures to many VOCs are associated with significant acute and chronic health problems. Despite the challenges in accurate measurement and identification of individual VOCs, we must understand, measure and manage occupant exposure to these compounds to create safe indoor environments.