Ceiling Limit 4 : Medicine. The maximum concentration of an airborne contaminant to which one can be exposed; the ceiling limits used are those published in 29 CFR 1910. 1000
NFPA 318 Standard for the Protection of Semiconductor Fabrication Facilities, 2002 ed. http://www.nfpa.org/assets/files/AboutTheCodes/318 /Errata318-02-2.PDF, (Std: Prot of Semiconductor Fabrication Fcilty - Amer) {297 NFC}