<Li> 0.00047 ppm or 0.47 ppb is the odor threshold, the point at which 50% of a human panel can detect the presence of an odor without being able to identify it . </Li> <Li> 10 ppm is the OSHA permissible exposure limit (PEL) (8 hour time - weighted average). </Li> <Li> 10--20 ppm is the borderline concentration for eye irritation . </Li> <Li> 20 ppm is the acceptable ceiling concentration established by OSHA . </Li>

At what concentration does hydrogen sulfide become explosive