"Porous material" means, for purposes of 35 Ill. Adm. Code 218 and 219, a substance that has tiny openings, often microscopic, in which fluids may be absorbed or discharged, including, but not limited to, paper and corrugated paperboard. Porous material does not include wood.
Ill. Admin. Code tit. 35, § 211.4900
Added at 34 Ill. Reg. 14119, effective September 14, 2010