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Volatil organic compounds - VOCs -, are all those hydrocarbons present in a gaseous state at normal ambient temperature, or which are very volatile at that temperature. An organic compound can be considered a VOC if at 20°C it has a vapor pressure of 0.01 kPa or more, or an equivalent volatility under the particular conditions of use - and a boiling point between 50 and 260°C.
VOCs are frequently released by solvents, paints, adhesives and other products commonly used in the cleaning and/or maintenance of buildings.
TVOCs are total organic compounds, the sum of all VOCs measured in indoor air (see point 2).
There are more than 120,000 chemical substances and more than 12 million published compounds. Of these, only a small fraction are studied from a medical perspective and there are limit values for only about 500 in the occupational/professional environment. Furthermore, in the residential environment there is no specific regulation with regard to VOC pollution - beyond recommendations or reference values.
This difficulty and the great variety of substances present in different types of buildings limits the individualized measurement of volatile organic compounds. For this reason, total volatile organic compounds - TVOCs - are used as a reference indicator for the presence of VOC/COVs in indoor air.
However, there is no normative consensus on which specific compounds define TVOCs. UNE-EN 16516:2018+A1:2021, ISO 16000-29:2014 or the study by Mølhave et al. among others, collect specific studies on the specific composition of TVOCs.
Therefore, when comparing TVOC levels between different monitoring scenarios or projects, it is necessary to first understand what is the exact definition or standard used to calculate TVOCs for that particular sensor.
In parallel, for an overall assessment of total organic compounds, the total air concentration in ppb (parts per billion) or µg/m³, of a ratio of alcohols, aldehydes, ketones, amines, siloxanes and aromatic and aliphatic hydrocarbons is measured according to the standard or reference procedure used to calculate TVOCs. However, other compounds with a more critical response on health, such as benzene, naphthalenes, cresols, or styrene, must be studied individually.
The most relevant TVOC standards and level recommendations are summarized below:
The reference values in My inbiot are based on the classification of total volatile organic compounds of the German Federal Environmental Agency, above which, depending on the exposure time, they can lead to allergic and sensitizing reactions, hypersensitivities or diseases of various pathologies.
Based on this classification, the following ranks have been established in My inBiot:
The concentration of total organic compounds in air is determined in ppb (parts per billion).
The relationship between ppb and µg/m³ is not straightforward, as the conversion of TVOC units depends on the specific compounds that define TVOCs and their molecular weights.
The technology used for continuous monitoring of TVOCs allows accurate and sensitive identification of the trend and amplitude of VOC concentration changes in the air. However, it is not a suitable technology for absolute quantification of volatile organic compounds. Therefore, it is possible to determine TVOC levels with relative units (Index Points). These relative measurements can be converted to absolute concentration using conversion factors.
The inBiot sensor is calibrated for ethanol. However, these ethanol-based ppb measurements can be converted to other reference gases using conversion factors. Some of the most common are isobutylene and Molhave gas mixture, used in RESET and WELL respectively.
TVOCMolhave[ppb]=0.58∗TVOCethanol[ppb].
TVOCMolhave[μg/m3]=4.5∗TVOCMolhave[ppb]=2.61∗TVOCethanol[ppb].
TVOCisobutylene[μg/m3]=2.3∗TVOCethanol[ppb].
Volatile organic compounds are present in solvents, paints, glues, varnishes and the like, in plastics, furniture, building materials (insulation, finishing boards, foams), cleaning, hygiene and maintenance products in buildings. They are common compounds, easily found in building interiors.
We spend between 80 and 90% of our time indoors. Our interrelationship with factors such as temperature, humidity, air renewal or the presence of volatile organic compounds characterize an adequate indoor environment and condition our health. An indoor environment without the presence of harmful volatile organic compounds will be an indoor environment focused on health, without the presence of irritating and/or potentially allergic substances, guaranteeing comfort and well-being, with positive impacts on the productivity and creativity of its occupants.
The risk from the presence of VOCs occurs mainly during the use of products containing VOCs and in the first days and weeks immediately after use. Some of the most common VOCs with the highest health impact are being replaced by alternative compounds. However, these have higher boiling points, so they can off-gas for longer and pose, like the VOCs they replace, significant health risks.
The health effects are diverse, depending on the compound and the period of exposure. VOCs are generally fat soluble and in the short term may cause allergic reactions, headache, mucosal irritation, itchy nose, red eyes, coughing, fatigue, dizziness or skin spots. In the long term, they can damage the liver, kidneys or the central nervous system, and some of them can be carcinogenic.
