EQUIPMENT DIVISION
1340 SEABOARD INDUSTRIAL BLVD
ATLANTA, GA 30301
PHONE: (404) 352-1680
FAX: (404) 350-6224
Regarding the Ozone Transport Commission Freeboard Requirement.
Briefly, the Ozone Transport Commission is a group of 12 states and the District
of Columbia forming the upper Middle Atlantic region through the Northeast.
Congress passed legislation in 1990 creating the Commission for developing a
unified approach to the growing ozone pollution problem in the Northeast. Since,
the organization has been assembling a plan and issuing guidelines to control
ozone and other emissions within the Commission states.
One aspect of this control was the issuance of a guideline to the states that “cold
solvent cleaners or degreasers” should have a freeboard ratio of 0.75. This
requirement was “borrowed” from the Halogenated Solvent NESHAPS (National
Emission Standards for Hazardous Air Pollutants). Due to the volatility of those
solvents, the U.S. EPA designated the 0.75 freeboard standard to reduce air
currents through the vapor zone of parts cleaners. The farther down the solvent is
in the machine (greater freeboard ratio) the better that it can retain the vapors
above the solvent layer. Freeboard is that portion of a tank’s or a tank-like
enclosure’s capacity that is not used for holding a liquid. In the absence of an
appropriate standard for less volatile hydrocarbon solvents, this ratio was adopted
by the Commission and other states, most notably Texas.
The freeboard ratio of a “cold solvent cleaner” or “cold solvent degreaser”, as
parts washers are called by regulatory agencies, is determined by dividing the
distance from the top of the solvent layer (solvent/air interface) to the top of the
machine by the lesser of the two dimensions of the machine top-opening.
The guideline for instituting a freeboard ratio for "cold solvent cleaners" is just
that, a guideline. The states are free to adopt alternate regulations. Some have,
such as Maryland and Pennsylvania, and use a volatility standard for the parts
washer solvent to override the freeboard ratio requirement.