Lots of factors play a part in the indoor air quality (IAQ) of a building. Volatile Organic Compounds (VOCs) are one of the most important.
Here, we’ll look at what they are, how they impact indoor air quality, and, crucially, how organisations can monitor VOC levels in their buildings to keep them within safe levels.
What are Volatile Organic Compounds?
They aren’t one specific substance, but rather a group of compounds emitted as gases into the air from products and processes. Things like paints, solvents, aerosols, pesticides, air fresheners, adhesives, cleaning products and disinfectants all produce VOCs. Office printers and copiers can be other sources of VOCs in buildings, and they are present in some printing materials like inks.
They’re also emitted from new furniture and carpets in a process known as ‘off-gassing’. Which means that, while it’s tempting to think of old buildings as being the worst culprits for air quality, new or newly renovated buildings can actually have higher levels of VOCs.
VOCs can also enter a building via polluted outdoor air.
Common examples of VOCs include:
- Benzine, emitted from petroleum
- Formaldehyde, common in many fabrics, coatings and building materials
- Acetone, found wallpaper
- Ethanol, found in paints
- Butanone, found in paints and other coatings, glues and cleaning products
- Ethylene glycol, used in industrial solvents, paints and detergents
- Methylene chloride, used for paint strippers, degreasing, cleaning and manufacturing
What are the impacts of VOCs on our health?
Exposure to VOCs can be a cause of sick building syndrome, where a building’s occupants experience an array of symptoms directly related to time spent there.
Detrimental effects on health can include headaches, dizziness, nausea and coughing. Other symptoms are things like eye, nose and throat irritation, fatigue and allergic skin reactions.
Long-term exposure has even been related to liver and kidney damage, as well as cancer.
All good reasons for keeping VOC levels in check. Plus, with strict indoor air quality regulations and guidelines now in place, like the WELL Buildings Standard, and IAQ Guidelines, organisations need to make sure they are conforming to the rules.
Good ventilation, no smoking indoors and careful attention to cleaning products and practices can all help.
But, crucially, one of the best things buildings managers can do is monitor their VOC levels to ensure they are within safe limits and identify trends.
How can VOC levels be monitored?
Because there are so many types of VOCs, they are often grouped together and monitored as TVOCs (Total Volatile Organic Compounds). They can be measured in micrograms per cubic meter (µg/m3) of air, milligrams per cubic meter (mg/m3), parts per million (ppm) or parts per billion (ppb)). Less than 0.3 mg/m3 are considered low TVOC concentration levels. And levels between 0.3 mg/m3 to 0.5 mg/m3 are acceptable.
Generally, the two most widely used technologies to measure total VOCs are Flame Ionisation Detection and Photo Ionisation Detection. Both technologies rely on the principle that when most organic vapours burn they produce positively charged carbon ions as an intermediate product of combustion.
These ions are collected on an electrode and an electrical current corresponding to the amount of carbon ions present is produced. If the instrument has been calibrated against a known source of carbon / VOCs a reading of the total carbon as parts per million (ppm) can be taken.
Further calculations can then be performed to infer the actual VOC concentration assuming the proportions of VOCs being measured is known eg 80% xylene, 20% isopropyl alcohol and assuming these proportions haven’t changed as part of the process.
However, these raw values can be tricky to interpret. Different buildings and environments will have different base VOC levels. You need to figure out if the VOC levels have changed ie if they’re higher or lower than the base level.
An air quality sensor that outputs a VOC index provides more actionable insights. Essentially, the sensor measures VOC levels over 24 hours and calculates the average value and assigns it VOC Index 100. Once the average is calibrated, the sensor can then monitor for changes. Values are measured on a range of 0-500. Values between 100 and 500 indicate deterioration, while values between 0-100 suggest improvements in air quality.
VOC Index of 100 continuously adapts to any environment. Therefore, conditions that were previously interpreted as average (VOC Index = 100) are now considered as air quality improvement.
How can this data be used?
Because index data is measured in near real-time and offers highly accurate specifics about VOC levels, this can be used to manage air quality within an office building. For example, levels above a certain value can trigger an alert to open a window or automate air conditioning or ventilation systems to kick in. It allows organisations to monitor overall air quality while also drilling down to specific spaces or locations which are above set thresholds so they can take action.
Pressac’s air quality sensor can measure VOC levels along with CO2, humidity, temperature and particulate matter levels, giving you clear insights into your building’s indoor air quality. Speak to us today to find out more.
The article was originally published in 2021 and updated on 14th Feb 2024.
