45CSR27, "To Prevent and Control the Emissions of Toxics Air Pollutants", addresses 14 compounds recognized
as "Toxic Air Pollutants" (TAPs) that are emitted by certain types of sources. All 14 TAPs are also included
in EPA's list of HAPs. A list of TAPs can be found in the rule at Table A of 45CSR27, or "45CSR27 Toxic Air
Pollutants", which also includes synonyms for the TAPs. The scope and purpose of 45CSR27 is to prevent and
control the discharge of TAPs from "chemical processing units" by requiring the application of Best
Available Technology (BAT), a standard specified in the rule. Table A of 45CSR27 sets a plantwide de minimus
level for each TAP, including fugitive emissions. If plantwide emissions of a particular TAP exceed the de
minimus level, then a case-by-case review of emissions is performed to ensure these meet the state standard
known as BAT.
For the purposes of 45CSR27, a "chemical processing unit" that may be subject to the rule has been defined
fairly broadly. Such a unit can include an assembly of reactors, tanks, distillation columns, heat
exchangers, vaporizers, compressors, dryers, decanters, and/or other equipment used to treat, store,
manufacture, or use TAPs. For the purpose of 45CSR27, a "chemical processing unit" also includes surface
coating equipment or similar equipment using a TAP as a solvent or for other purposes, but does not include
equipment used in the production and distribution of petroleum products providing that such equipment does
not produce or contact materials containing more than 5% benzene by weight. Fugitive emissions, wastewater
from "chemical processing units," railcar and tank truck loading and unloading, are also subject to BAT
standards.
BAT is an emissions limit requiring the application of the maximum degree of reduction and control which the
Director, on a case-by-case basis, determines is achievable for each toxic air pollutant which would be
emitted from any stack, pipe, air pollution control device, or from any other equipment or facilities
associated with a chemical processing unit.
In the case of "chemical processing units" constructed or modified after the June 30, 1990, effective date
of this rule, BAT shall not be less stringent than the most stringent emissions level that is achieved in
practice by similar sources or processes. For existing "chemical processing units," BAT may be less
stringent than requirements for new or modified units. For all facilities, BAT shall represent the maximum
degree of emission reduction that the Director determines is achievable taking into consideration the cost
of achieving such emission reduction, and public health and environmental impacts. All BAT programs shall
fully consider the additive or cumulative health and environmental impacts of multiple pollutant and
multiple unit emissions. No BAT proposal shall be approvable that represents a level of control less
stringent than any requirement for a "chemical processing unit" under 40 CFR 61 and 40 CFR 60. The DAQ
typically uses a "top-down" approach to determine BAT.
The chart, "45CSR27 - Best Available Technology (BAT) for Toxics Air Pollutants (TAPs) - Applicability
Determination" is designed to illustrate the major steps in determining applicability to 45CSR27 and BAT, as
well as briefly describe the "Top-Down" process used to determine BAT.