Federal Circuit Affirms Indefiniteness of the Term “About”

In Enviro Tech Chemical Services, Inc., v. Safe Foods Corp., No. 2024-2160 (Fed. Cir. May 4, 2026), the Federal Circuit affirmed a district court’s determination that all asserted claims of U.S. Patent No. 10,912,321 were invalid as indefinite.

Enviro Tech sued Safe Foods for infringement of the ’321 patent, which relates to methods of treating poultry during processing to increase weight. The asserted claims recite “a pH of about 7.6 to 10,” and Safe Foods argued that the term “about” is indefinite. The district court agreed, determining that the intrinsic evidence failed to inform a skilled artisan as to the scope of “about” with reasonable certainty.

The Federal Circuit affirmed. First, the Court determined that the claims themselves provided no guidance as to the degree of deviation encompassed by “about.” Second, the Court found that the specification provided conflicting guidance on acceptable pH variance that “about” could encompass because it applied differing deviations in pH ranges across experiments. Third, the Court concluded that statements made during prosecution did not clarify the scope of “about” because Enviro Tech neither defined the term nor applied it consistently, at times arguing it was material to some claims and immaterial to others. The Court also noted that amendments narrowing the claimed pH range to overcome prior art heightened the need for clarity in defining the scope of “about,” reinforcing its conclusion that the claim term is indefinite.