Much ink has been spilled over the meaning of “about” when used to characterize an amount or a range recited in a patent claim. Sometimes the patent explicitly defines “about,” sometimes “about” simply means “approximately,” sometimes the scope of “about” is clarified based on arguments made during prosecution to gain allowance, and sometimes a skilled artisan might recognize the scope of “about” based on some constellation of the foregoing and knowledge in the art. But sometimes the meaning of “about” is not certain based on the unique facts of the case, and the patent claim is indefinite. Earlier today, the Federal Circuit addressed this last scenario.
In Enviro Tech Chemical Services, Inc. v. Safe Foods Corp., No. 2024-2160 (May 4, 2026), the Federal Circuit affirmed a district court judgment finding the term “about” indefinite as used in the asserted poultry processing claims. The patent claims recited methods for treating poultry during processing with peracetic acid to
