Our Patent Case Summaries provide a weekly summary of the precedential patent-related opinions issued by the Court of Appeals for the Federal Circuit and the opinions designated precedential or informative by the Patent Trial and Appeal Board.
Enviro Tech Chemical Services, Inc. v. Safe Foods Corp.
No. 2024-2160 (Fed. Cir. (E.D. Ky.) May 4, 2026). Opinion by Lourie, joined by Prost and Burroughs (sitting by designation).
Enviro Tech sued Safe Foods for infringement of a patent directed to methods for treating poultry during processing for increasing the weight of the poultry, using “peracetic acid.”
During claim construction, Safe Foods alleged that two claim terms were indefinite, including the term “about” in claim language reciting that the acidity of a peracetic acid-containing water will be altered to a “pH of about 7.6 to about 10.” The district court agreed and issued a judgment that the asserted claims were invalid. Enviro Tech appealed.
The Federal Circuit affirmed. To begin, the court explained that it has “long held that words like ‘about’ and ‘approximately’ may be appropriately used to avoid a strict numerical boundary to the specified parameter.” The court continued: “Terms of degree, like ‘about’ and ‘approximately,’ are not inherently definite or indefinite. … When a word of approximation is used, however, the parameter’s range must be reasonably certain based on the technological facts of the particular case.”
The court analyzed the record for the Enviro Tech patent and its use of the term “about.” Beginning with the claim language, the Federal Circuit ruled that the claims “do not provide any guidance on how much below a pH of 7.6 or above a pH of 10 the peracetic acid-containing water can be to meet the limitation.”
Next, the Federal Circuit ruled that the specification “similarly does not inform a skilled artisan of the scope of ‘about’ with reasonable certainty.” The specification recites “numerous experiments,” and in many cases the experiments proceeded only “when the difference of the actual pH was less than or equal to 0.3 of the target pH.” But in other cases the experiments had deviations between 0.35 and 0.5 of the target pH. The Federal Circuit ruled that the specification’s “conflicting guidance” does not allow a skilled artisan to determine the scope of “about” with reasonable certainty.
Finally, the prosecution history also failed to inform a skilled artisan of the claim scope with reasonable certainty. Enviro Tech had “treated the term inconsistently,” and “at no point in the entire prosecution” did it explain what “about” means.
The Federal Circuit also noted that “an important determinant in our decision here is the very fact that what is now claim 1 was amended in respect to pH to avoid prior art, which was as close as a pH of 7.0.” The court concluded that “when the specification recites pHs of 6–10, and the prior art pH of 7.0 required the claims to be amended, the definiteness requirement of § 112 necessitates much more clarity than using the vague term ‘about.’”