Gas filters - do they protect against isocyanates?
Publish date: 2001-01-01
Report number: FOI-R--0222--SE
Pages: 42
Written in: Swedish
Abstract
In some workplaces isocyanic acid (ICA) and methyl isocyanate (MIC) can be present as air pollutants at high concentrations. The use of individual respiratory protection is therefore sometimes necessary. In many cases air-purifying respirators have been found to be the only practically feasible solution. However, there has been a large uncertainty about the effectiveness of gas filters against these low-boiling isocyanates. In order to check the usefulness of gas filters against low-boiling isocyanates we have determined breakthrough curves for ICA and MIC for a number of gas filters. To be able to determine breakthrough levels down to 0.05 ppb the effluent gas was absorbed in a series of gas wash bottles with dibutylamine in toluene. The resulting urea derivatives were then analysed by GC-MS. The results show that ICA is taken up efficiently by the tested gas filters. As a rule MIC is taken up less efficiently. Hight relative humidity was found to have a very negative effect on the protection against MIC, whereas the protection against ICA was less affected. However, it was possible to find gas filters that gave good protection against MIC also at high relative humidity.