‘About’ Indefinite Where Intrinsic Evidence Is Inconsistent

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 decision holding that the asserted claims of U.S. Patent No. 10,912,321 are invalid as being indefinite. The ’321 patent is directed to methods of treating poultry during processing to increase the weight of the poultry using peracetic acid. Claim 1 recites, in pertinent part, “altering the pH of the peracetic acid containing water to a pH of about 7.6 to about 10 by adding an alkaline source.” Safe Foods contended, and the district court agreed, that the term of degree “about” rendered the asserted claims indefinite. In affirming, the Federal Circuit reiterated that “terms of degree, like ‘about’ and ‘approximately,’ are not inherently indefinite,” but concluded that the intrinsic evidence failed to inform a skilled artisan, with reasonable certainty, of the permissible deviation from the claimed range. The ordinary meaning of “about” as