Isocyanates
Description
Isocyanates are a family of highly reactive, low molecular weight liquid compounds with a general formula of R-NCO. Isocyanates are generally colourless and can commonly can be detected by a sweet and pungent odour..
Many isocyanate compounds are extremely flammable and toxic. The most common isocyanates are MDI, TDI, HDI and IPDI, which are di-isocyanates (DI), these consist of two isocyanate groups.
Sources
Isocyanates are not naturally occurring and are produced from amines by phosgenation using phosgene (COCl2). They are used by chemical and coating industries for products which include paints, coatings, foams, glues and flooring. Certain tasks, such as spraying can result in high exposure to isocyanates..
Environmental Impact
Isocyanate atmospheric pollution is commonly found in urban areas. Most isocyanates react with water in the environment to further produce toxic fumes. Furthermore, when they are heated to high temperatures, they can decompose to emit oxides of nitrogen and cyanide compounds.
Control
Workplace isocyanate concentrations are commonly controlled using closed mechanical ventilation systems to reduce indoor isocyanates levels. The exhausts of these systems emit isocyanates into the atmosphere, in some processes isocyanates in gaseous streams are reduced to very low levels by thermal destruction.
Measurement
Alkali Environmental perform periodic measurements of isocyanates in gaseous streams from stationary sources in line with the standard reference method US EPA CTM 036. We are currently working towards accreditation for this method whereby the reported results will 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.