35 Ill. Adm. Code 215.241
External Floating Roofs
Section 215
Section 215.241Â External
Floating Roofs
The requirements of subsection
215.124(a) shall not apply to any stationary storage tank equipped with an
external floating roof:
a)Â Â Â Â Â Â Â Â Exempted under Section 215.123(a)(2) through (a)(6);
b)Â Â Â Â Â Â Â Â Of welded construction equipped with a metallic-type shoe seal
having a secondary seal from the top of the shoe seal to the tank wall
(shoe-mounted secondary seal);
c)Â Â Â Â Â Â Â Â Of welded construction equipped with a metallic type shoe
seal, a liquid-mounted foam seal, a liquid-mounted liquid-filled-type seal, or
other closure device of equivalent control efficiency approved by the Agency in
which a petroleum liquid with a true vapor pressure less than 27.6 kPa (4.0
psia) at 294.3º K (70º F) is stored; or
d)        Used to store crude oil with a pour point of 50º F or higher
as determined by ASTM Standard D97-66 incorporated by reference in Section
215.105.