Volatile Organic Compounds
Volatile Organic Compounds (VOCs) are a group of gaseous pollutants with high vapour pressure and low solubility in water. There are over several hundred variations of VOCs the majority of which are colourless and highly flammable.
Total VOC is a way of expressing the concentration or mass of a mixture of VOCs in a common reference unit, most often carbon (C). Speciated VOC is a way of refering to a particular individual species or collection of VOCs, for example Formaldehyde (individual) or Aldehydes (aldehyde functional group species).
VOCs are found in a wide range of household and manufactured products, these include paints, paint thinners, degreasers, fuels and aerosols. They can be emitted to atmosphere in both product manufcturing and product end use.
Particular species of VOCs are considered to be highly toxic with potential health impacts including respiratory difficulties, nausea to severe organ and nerve damage.
VOCs can react with oxides of nitrogen in sunlight to form photochemical smog and ground level ozone which is a potent greenhouse gas..
Often the most effective way of reducing VOC pollutants is through substitution of the chemical constituents with water-based or less-volatile alternatives in manufacturing process. Where substitution is not sufficient or possible, volatile organic compounds can be removed from waste gas streams by adsorption, condensation and thermal destruction.
A common way of preventing VOCs entering the atmosphere in manufacturing is by thermal destruction using thermal oxidisers. These are high temperature incinerators which decompose the VOCs to chemically oxidise the hydrocarbons into primarily carbon dioxide (CO₂) and water (H₂O), before being released into the atmosphere..
Alkali Environmental perform periodic measurements of Total VOCs in ducted emissions from point sources to the standard reference method BS EN 12619. The reported results carry UKAS and MCERTS accreditation where the method can be performed to the standard.
These measurements are taken using an on-line flame ionisation-detector analyser where instantaneous and logged results can be taken. In combustion based processes, reported results are often corrected for oxygen concentration to avoid the affect of dilution air on the result.
Alkali Environmental perform periodic measurements of Speciated VOCs in ducted emissions from point sources to the standard reference method CEN/TS 13649. The reported results carry UKAS and MCERTS accreditation where the method can be performed to the standard.
These measurements are taken using a manual sampling train whereby a single result is obtained for a gas sample taken from the duct. In combustion gases the reported results are often corrected for oxygen concentration to avoid the affect of dilution air on the result.
Some examples of common carbon monoxide emission limits:
20-50mg/m³ – Thermal Oxidisers
20mg/m³ – Cremators
1000mg/m³ at 5% O₂ – Landfill Gas / Biogas Engines (LFTGN08, post-2005)
1750mg/m³ at 5% O₂ – Landfill Gas / Biogas Engines (LFTGN08, pre-2006)