Background information: Volatile organic compounds
VOC (Volatile Organic Compounds)
What are VOCs and where do they come from?
The English abbreviation "VOC" stands for volatile organic compounds, which are present in the air in gaseous or vapor form at room temperature.
Many solvents, liquid fuels and synthetically manufactured substances may be present as VOCs, but also many organic compounds which are formed in biological processes. Humans and animals give off VOC through breathing or directly from the skin.
The following table shows some typical VOCs for interior spaces and their sources:
| Typical pollutants (VOCs) in interior spaces and their sources | ||
|---|---|---|
| Causes | Emissions source | VOC |
| Humans and animals | Breath | Acetone, ethanol, isoprene |
| Perspiration and transpiration | Nonanal, decanal, α-Pinene | |
| Flatus | Hydrogen, methane | |
| Cosmetics | Limonene, eucalyptol | |
| Household materials | Alcohols, esters, limonene | |
| Combustion (motors, ovens, cigarettes) |
Unburned hydrocarbons | |
| Building materials, furniture, office equipment, consumer products |
Paints, varnishes, adhesives, solvents, carpets |
Formaldehyde, alkanes, alcohols, aldehydes, ketones, siloxanes |
| PVC | Toluol, xylol, decane | |
| Printers/copiers, computers | Benzene, styrol, phenol | |
The following guide values can be used for evaluating the measuring result:
| Guide values for air quality evaluation | ||||
|---|---|---|---|---|
| Level | Hygiene level | Recommendation | TVOC [ppb] | CO2 [ppm] |
| 5 Unhealthy | Situation unacceptable | Use only if unavoidable -Intensive ventilation required |
2200+ | 2000+ |
| 4 Poor | Very concerning | - Increased ventilation -Ventilation required - Search for sources |
660-2200 | 1600-1900 |
| 3 Moderate | Concerning | - Increased ventilation -Ventilation recommended - Search for sources |
220-660 | 1100-1500 |
| 2 Good | No relevant concerns | Ventilation recommended | 65-220 | 700-1000 |
| 1 Very good | No concerns | Target value | 0-65 | 0-600 |
VOCs and room air quality
VOC/CO2
(450-2000 ppm)
%RH
(5–95%)
°C
(0–50 °C)
The quality of room air is not felt by persons only according to the actual values of temperature and relative humidity. Odors in the air are a significant reason why people feel unwell in such areas and feel compelled to quickly leave the space.
Examples which we all know from experience include poorly ventilated offices and business, commercial kitchens, fitness centers and toilets and washrooms.
VOC in indoor spaces can also have a serious affect on health: Eye and sinus irritations as well as headaches, fatigue, lack of concentration and diminished performance - also known as "Sick Building Syndrome" (SBS) - may be a consequence of VOC in indoor spaces.
Reason enough to measure and control the presence of VOC!
Measure air quality with a VOC sensor
CO2 sensors are mostly used for ventilation control in office buildings, schools, educational and sports facilities. But since odors caused by VOC have little or no influence on the determined CO2 values, they are hardly detected by CO2 measurement. The consequence: Although there is an actual ventilation need, this condition is not recognized using traditional approaches.
As a rule the rise of VOC in indoor spaces is caused by humans - whether from breathing, perspiration or as a consequence of human activities. Therefore a rise in VOC over the base level in the room can be used as a good indicator for the presence of persons in the monitored area.