Safe-use times for chemical suits
06 February 2017
Chemical Permeation tests on chemical suit fabric are conducted at 23oC. Yet permeation rate increases with temperature. So if the real-world temperature is higher than 23oC, the permeation rate will be higher than indicated by the test and any test-based calculation of safe use time will be wrong, explains Lakeland Industries Europe.
This can easily be shown graphically. The Permasure Toxicity Risk Calculator calculates time to reach the chemical toxicity limit for chemicals at temperatures between -10oC and 50oC. As an example, the graphs shown indicate the effect of temperature on both permeation rate and calculated safe use time for Dichloromethane against a ChemMax 3 coverall.
Graph 1 shows the effect of temperature on permeation rate, indicating it increases from - 0.2 µg/min/cm2 at 15oC, to - 1.7 µg/min/cm2 at 45oC.
Graph 2 shows the effect on the “Safe-Use Time”, i.e. the time it takes to reach the toxicity threshold for the chemical, based for dichloromethane on a toxicity threshold of 20 µg/min/cm2.
Safe-Use Time reduces from over 100 minutes at 15oC to less than 20 minutes at 45oC.
This example illustrates two important points:-
- The fact that permeation tests are conducted at 23oC is ONE reason why they cannot be used to indicate whether or how long a chemical suit will provide protection in a given situation. Unless the application temperature is at the same temperature as the test, the results of the test are meaningless.
- The analysis above has been made using the free Permasure Toxicity Calculation tool available for Lakeland’s ChemMax 3, ChemMax 4 and Interceptor coveralls. It shows how Permasure can contribute key information to a risk assessment for a chemical protection application. Permasure can be used as a tool to more effectively manage safety in real world applications by indicating safe-use times at varying temperatures, thus enabling safety managers to manage tasks in order to improve protection for workers using hazardous chemical suits.