Vapour hazard index

Phosgene has been included in various hazard rating systems in which the actuai hazard, rather than just toxicity, is evaluated [1206,1623,1957]. A vapour hazard index (a measure of the amount by which a saturated atmosphere of a materiai exceeds the TLV) for phosgene is estimated to be 10000. The index takes account of the volatility of the material, in addition to its toxicity for comparison the value for dichlorine is 1000 [1623]. 

A number of phosphate and thiophosphate esters are of limited thermal stability and undergo highly exothemiic self-accelerating decomposition reactions which may be further catalysed by impurities. The potential hazards can be reduced by appropriate thermal control measures. An example is the substitution of hot water at 60 C for pressurised steam to melt a solid phosphate ester, which on adiabatic calorimetric examination was found to have a time to maximum decomposition rate of 6 h at 110° but 11 h at lOO C [2]. The combined use of vapour phase pyrolysis to decompose various phosphoms esters, and of GLC and mass spectrometry to analyse the pyrolysis products, allowed a thermal degradation scheme to be developed for phosphorus esters [3]. Individually indexed compounds are ... 

Degreasing solvent Degreasing efficacy (%) Health hazard Aquatic hazard" Vapour pressure at 20 (hPa) CO2 emission potential (Tm CO2I Tm) Renewable mass index (%)... 

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