Quote Originally Posted by John Stevens View Post
For a person who will be exposed to the dust for up to ten hours a day, and up to 40 hours a week, the "permissible exposure limit" for "total dust" is 15mg/m^3. If you limit the dust to what is called the "respirable fraction," the limkt is 5mg/m^3, still five times the figure stated in the earlier thread. OSHA also gives these exposure limits as particle numbers as measured by "impinger samples counted by light-field." These particle number limits are 50 million particles/cu.ft. for total dust and 15 million particles/cu.ft. for the respirable fraction of dust.
John,

Thanks for that very informative post. Do you have any idea what particle size they were talking about for those impinger samples. Those limits seem quite high relative to the numbers I have been seeing where the highest reading is was about 50,000/cu ft. Perhaps they measure smaller particle sizes.

Greg