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i/ ° � � �1*3>.5.� � . / ,� � ��y,�� R} a .. ��1`.. . � � ,. / /` � ; �� 1 •�,� : , � �,� �. � J f.y°::: ". �� '; � �� #' �Mi:'""':-':' . � . � �! � t � ( F � ..:._ `{ � S c . :� . ` � i ! � . � k r `a � A baghouse is a large filteri�ng device that removes particulate matter in the process air from HMA production. A large fan on the outlet end of the baghouse pulls dirty air from the drum into the filter unit. Hundreds of long cylindrical cloth bags hang in rows within the filter section. The air is pulled through the bags and dust par- ticles collect on the bags' outer surface. Filtered air is released into the atmosphere through the exhaust stack. Collected dust is frequently removed from the bags and conveyed to the mixer to be added to the asphalt pavement mixture. Baghouses filter out virtually all of the particulate from the air stream (over 99.9%�. The Clean Air Act states that HMA facilities cannot emit more than 0.04 grains (grain = 1/7000th of a pound) of particulate matter per dry standard cubic foot of air. Most baghouses routinely emit less than half of the allowable particulate matter. � i � ' . �, � ,, _-� � � � a;- . } � rv 4, s; � : . { . �- f �� . _ I I �' The Clean Air Act of 1990 requires that all stationary emission sources obtain air permits in order to operate, including hot mix production facilities. An air permit contains the operating conditions that must be met by the faciliry. Particulate emissions and opacity are regulated on a federal basis, though many states have implemented tighter requirements. individual states and local authorities regulate other pollutants, including the products of combustion. Facilities must maintain extensive records to demonstrate compliance with those regulations. This includes production and fuel consumption rates from which emission levels can be calculated. Failure to comply with operating permit conditions results in fines and/or facility shut down. , f I I ' � . .� _� � � . ��I� _ . . i ` I �- � ` Federal requirements in the Clean Air Act mandate that all permitted emission sources must be stack tested within 180 days of startup. Subsequent testing requirements are determined by individual states and permitting authorities. For example, some states require yearly testing while others may only require the initial test as long as permit operating conditions are met. �. _ _ . _ . .: _ � _ . ;:: : , ._ .6o-�c`�..;xr_�eN..N:�S i�w`.z,e E,��.�L_'�rm �5r a%a•,�s.�o+s.cW:ax?r:'°�' 'w.e�.4. <;: ;.,,.. �,+6�4i'n..,�s4�m��W .�m�a'3H,i:%�,;r.Xun`w "� .<'�°'��.,�.n.;.-.