ISRP 2000 abstract
| Presenter/author | Title | Abstract |
| Jonsson, Per-Gunnar
Asst Dir of Research, FOA NBC Defence, Umeå, Sweden |
Protection performance of activated carbon filters against methyl isocyanate | Polyurethanes
are a group of frequently used polymers. If polyurethane-containing
objects are heated (higher than about 160°C), a large number of
degradation products are formed. Among these are very toxic low
molecular weight isocyanates, such as methyl isocyanate. The very low
Swedish occupational exposure limit of 0.005 ppm for all types of
isocyanates has been found difficult to maintain in quite a few
workplaces where polyurethanes and some other nitrogen-containing
plastics are heated. The use of individual respiratory protection is
therefore necessary in many cases. Although the preferred method of
protection is supplied air respirators, in some cases air purifying
respirators have been found to be the only practically feasible
solution. However, there have been some doubts about the efficiency of
gas filters against low molecular weight isocyanates.
In order to check the usefulness of gas filters against low boiling isocyanates we have determined breakthrough curves for methyl isocyanate for a number of gas filters containing various commercially available activated carbons. To be able to determine breakthrough levels lower than 0.001 ppm the effluent gas was absorbed in a series of wash bottles with dibutylamine in toluene. The resulting urea derivative was then analysed by GC-MS. In this way breakthrough curves for a number of activated carbon filters could be determined. There were large variations in performance for the various carbons. High relative humidity was found to give shorter protection times. |