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Why to measure TVOC or indoor air quality?

Sensors in an HVAC environment


VOC - Volatile Organic Compounds
Volatile Organic Compounds or VOCs are organic chemicals that become a gas at room temperature and are the main origin of air pollution at ground level. A common term used when measuring and eliminating VOCs is “Total VOC” or TVOC. TVOC means the total concentration of multiple VOCs present simultaneously in the air.

The human contribution to indoor air pollutants has been historically correlated with CO2, which is commonly used as an indicator for insufficient ventilation in closed spaces, but this doesn’t cover the complete load.
VOCs or Volatile organic compounds are known to cause eye, nose and throat irritations, headache, drowsiness, dizziness, nausea, difficulty concentrating and fatigue. VOCs in indoor environments evaporate from substances such as cleaning products, adhesives, paints, new carpets, copiers and printers to building materials and furnishings. VOCs are also emitted from humans and animals in their breath, sweat and directly from their skin.

Among many VOCs, TVOC sensors have an increased selectivity to hydrogen (H2). In indoor environments, the H2 concentration is expected to correlate well with the CO2 concentrations as human breath contains significant concentrations of both CO2 (4 %) and H2 (10 ppm). Furthermore, humans are the major source of CO2 and H2 in typical indoor environments. This makes it possible to distinguish the influence of human presence from other contaminants and control the ventilation system based on occupation of a space.

Ventilation in function of TVOC level is interesting in environments where indoor air quality need to be optimised on continuous base, such as living room, office buildings, certain industrial environments, etc.