Indoor air often contains volatile organic compounds (VOCs), and their levels vary a great deal from place to place and over time. Concentrations are affected by factors such as the use of the space, building materials, maintenance history, ventilation, temperature and humidity. Pollutants from outdoors can also raise VOC concentrations.
VOCs can be divided into different groups, for example:
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aliphatic and aromatic hydrocarbons
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terpenes
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alcohols and ethers
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aldehydes, acids, ketones and esters
These compounds can be measured in two ways:
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Sampling methods, where an air sample is taken and sent to a laboratory for analysis.
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Continuous measuring devices, such as Loop One, which measure VOC concentrations in real time.
Results from sampling and continuous measurements cannot be compared directly with each other, nor can they be used as such to assess health effects. For example, the limit values laid down in the Housing Health Decree apply only to collected samples.
How the measurements work
In the laboratory, samples are analysed using a standardised method (SFS-EN ISO 16000-6:2021) with Tenax TA as the adsorbent and TD-GC-MS as the analytical technique. This allows individual compounds to be identified precisely.
Continuous measuring devices do not identify individual compounds; instead, they measure the total concentration of VOCs. This makes it possible, for example, to detect momentary emission peaks or to monitor concentrations over the long term. In this way, potential emission sources can be identified and corrective action taken.
A practical example from a museum
In a museum, continuous measurement showed VOC concentrations rising whenever the ventilation unit was running. A new rubber mat had been installed in the space, and its odour had also been noticed. Visitors, however, had not complained about the smell.
Based on the results, an additional measurement was carried out using the sampling method. The analysis showed that the indoor air contained a compound associated with rubber mats, but the concentrations did not exceed the official limit values. It is worth remembering, however, that odour nuisance can occur even before concentrations exceed the threshold of harm – people differ in how sensitive they are to smells.
Summary
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Continuous measurement helps to detect VOC emission peaks in indoor air. Short-lived peaks are usually harmless, but elevated concentrations lasting several hours or days may indicate a problem, and their causes should be investigated.
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Laboratory measurements complete the picture and make it possible to identify individual compounds.
VOCs are a useful parameter to monitor in all kinds of buildings. In addition to sensory observations and user experiences, it is worth keeping track of them by measuring.