10 Control of Volatile Organic Compounds(VOCs) Volatile organic compounds(VOCs)are liquids or solids that contain carbon(carbon bonded to carbon, hydrogen, nitrogen, or sulfur, but not carbonate carbon aCOs nor carbide carbon as in CaC2 or Co or CO2), which vaporize at significant rates are probably the second-most widespread and diverse class of emissions after particulates VOCs are a large family of compounds. Some(eg, benzene)are toxic and carcinogenic, and are regulated individually as hazardous pollutants. Most VOCs are believed not to be toxic (or not very toxic) to humans. Our principal concern with vOCs is that they participate in the"smog reaction and also in the formation of secondary particles in the atmosphere. These latter are mostly in the fine particle size range. Some VOCs are powerful infrared absorbers and thus contribute to the problem of global warning 10.1 VOCs We may now state, as an approximate rule, that VOCs are those organic liquids or solids whose room temperature vapor pressures are greater than about 0.01 psia(=0.0007 atm) and whose atmospheric boiling points are up to about 500 F( 260C), which means most organic compounds with less than about 12 carbon atoms. Materials with higher boiling points evaporate quite slowly into the atmosphere unless they are heated, and hence they are less likely to become art of our VOC problems. (If vaporized, they condense in the atmosphere, forming part of our fine particle problem. A lighted cigarette produces a gaseous mixture of high-boiling organic compounds; when this mixture is cooled on leaving the cigarette it forms a smoke of fine articulate droplets. They are part of our particulate problem, but not our VOC problem.) he legal definition used for regulatory purposes does not set a lower vapor pressure limitation and excludes a large variety of fetal bottle compounds Sealing washer photochemical reactivity, including methane, ethane, and most halogenated with boiling points above about 500-F will have negligible emission rates under normal circumstances. so the ab sence of a lower limitation causes little The terms VOC and hydrocarbon(HC) are not identical. but often are practically identical. Strictly speaking, a Sealing waher hydrocarbon contains only hydrogen and called a"hydrocarbon fuel"because it contains mostly hydrogen and carbon atoms, but also some oxygen, nitrogen sulfur atoms Acetone al ingredient of nail polish remover, is a voc but is not strictly speaking a hydrocarbon because it contains an oxygen atom. In common usage it would often be grouped with the hydrocarb ons Cuff is not attached Fig. 10-1 Three kinds of seals:(a) a static seal, as side cuff es exists between a carbonated beverage bottle and its Flexible bottle caps;(b)a packed seal, as exists between the valve stem and valve body of simple faucet and as alse trainNmIssIor exists on many simple pumps;(c)a rotary seal of the sone pumps10－1 10 Control of Volatile Organic Compounds(VOCs) Volatile organic compounds (VOCs) are liquids or solids that contain organic carbon (carbon bonded to carbon, hydrogen, nitrogen, or sulfur, but not carbonate carbon as in CaCO3 nor carbide carbon as in CaC2 or CO or CO2), which vaporize at significant rates. VOCs are probably the second-most widespread and diverse class of emissions after particulates. VOCs are a large family of compounds. Some (e.g., benzene) are toxic and carcinogenic, and are regulated individually as hazardous pollutants. Most VOCs are believed not to be toxic (or not very toxic) to humans. Our principal concern with VOCs is that they participate in the "smog" reaction and also in the formation of secondary particles in the atmosphere. These latter are mostly in the fine particle size range. Some VOCs are powerful infrared absorbers and thus contribute to the problem of global warning. 10.1 VOCs We may now state, as an approximate rule, that VOCs are those organic liquids or solids whose room temperature vapor pressures are greater than about 0.01 psia (= 0.0007 atm) and whose atmospheric boiling points are up to about 500 。 F (= 260。C), which means most organic compounds with less than about 12 carbon atoms. Materials with higher boiling points evaporate quite slowly into the atmosphere unless they are heated, and hence they are less likely to become part of our VOC problems. (If vaporized, they condense in the atmosphere, forming part of our fine particle problem. A lighted cigarette produces a gaseous mixture of high-boiling organic compounds; when this mixture is cooled on leaving the cigarette it forms a smoke of fine particulate droplets. They are part of our particulate problem, but not our VOC problem.) The legal definition used for regulatory purposes does not set a lower vapor pressure limitation and excludes a large variety of compounds that have negligible photochemical reactivity, including methane, ethane, and most halogenated compounds. Compounds with boiling points above about 500~F will have negligible emission rates under normal circumstances, so the absence of a lower vapor pressure limitation causes little problem. The terms VOC and hydrocarbon (HC) are not identical, but often are practically identical. Strictly speaking, a hydrocarbon contains only hydrogen and carbon atoms. But gasoline is normally called a "hydrocarbon fuel" because it contains mostly hydrogen and carbon atoms, but also some oxygen, nitrogen, and sulfur atoms. Acetone, CH3-CO-CH3, the principal ingredient of nail polish remover, is a VOC but is not strictly speaking a hydrocarbon because it contains an oxygen atom. In common usage it would often be grouped with the hydrocarbons. Fig. 10-1 Three kinds of seals: (a) a static seal, as exists between a carbonated beverage bottle and its bottle caps; (b)a packed seal, as exists between the valve stem and valve body of simple faucet, and as also exists on many simple pumps; (c)a rotary seal of the type common on the drive shafts of automobiles and some pumps