means any compound of carbon,excluding carbon monoxide,carbon dioxide,carbonic acid,metallic carbides or carbonates,and ammonium carbonate,which participates in atmospheric photochemical reactions.
This includes any such organic compound other than the following，which have been determined to have negligible photochemical reactivity：methane；ethane；methylene chloride (dichloromethane)；1,1,1-trichloroethane(methyl chloroform)；1,1,2-trichloro-1,2,2-trifluoroethane(CFC–113)；trichlorofluoromethane(CFC–11)；dichlorodifluoromethane(CFC–12)；chlorodifluoromethane(HCFC–22)；trifluoromethane(HFC–23)；1,2-dichloro 1,1,2,2-tetrafluoroethane(CFC–114)；chloropentafluoroethane(CFC–115)；1,1,1-trifluoro 2,2-dichloroethane(HCFC–123)；1,1,1,2-tetrafluoroethane(HFC–134a)；1,1-dichloro 1-fluoroethane(HCFC–141b)；1-chloro 1,1-difluoroethane(HCFC–142b)；2-chloro-1,1,1,2-tetrafluoroethane(HCFC–124)；pentafluoroethane(HFC–125)；1,1,2,2-tetrafluoroethane(HFC–134)；1,1,1-trifluoroethane (HFC–143a)；1,1-difluoroethane (HFC–152a)；parachlorobenzotrifluoride (PCBTF)；cyclic，branched，or linear completely methylated siloxanes；acetone；perchloroethylene (tetrachloroethylene) and perfluorocarbon compounds which fall into these classes：
(i)Cyclic, branched, or linear, completely fluorinated alkanes;
(ii)Cyclic, branched, or linear, completely fluorinated ethers with no unsaturations;
(iii)Cyclic, branched, or linear, completely fluorinated tertiary amines with no unsaturations; and
(iv)Sulfur containing perfluorocarbons with no unsaturations and with sulfur bonds only to carbon and fluorine.
the air quality guidelines for specific substances,while they do not refer to specific environmental settings,may be difficult to apply to the indoor environment.for example,the relevant compounds often occur in mixtures at higher concentrations indoors than they do in outdoor air,thus providing multiple exposures.Indoor air samples may typically contain 100 or more VOCs at concentrations in the range of 1 to 100 ?/? each.
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