Enviro Tech Chemical Services v. Safe Foods Corp.: How the Federal Circuit’s “About” Decision Highlights the Importance of Precision in Patent Claim Drafting
Patent claims are often described as the legal boundaries of an invention. They define what a patent owner can prevent others from making, using, selling, or importing. Yet drawing those boundaries is rarely straightforward, particularly in fields where scientific measurements naturally involve some degree of variability. For companies operating in highly technical industries, especially chemical, pharmaceutical, biotechnology, and materials science fields, claim language must walk a difficult line.
Claims must be broad enough to provide meaningful protection against competitors that “design around” the invention. At the same time, claims must be precise enough that the public can understand the limits of the exclusive rights being granted.
The Federal Circuit’s decision in Enviro Tech Chemical Services illustrates what happens when a patent claim attempts to achieve flexibility (and breadth) through terminology that may be too uncertain. The case centered on whether the patent's use of the word "about" in defining a claimed pH range provided a person of ordinary skill in the art with reasonable certainty regarding the scope of the invention, as required by the definiteness requirement of U.S. patent law.
The court’s decision serves as an important reminder for patent applicants and practitioners: words that appear ordinary in everyday language can create substantial legal uncertainty when used in patent claims. For companies developing chemical processes, formulations, and industrial technologies, the case provides valuable lessons about:
How courts interpret terms of degree such as “about,” “approximately,” and “substantially.”
Why numerical ranges require careful drafting.
How experimental data and patent specification influence claim scope and definiteness.
Why patent applicants should consider how a competitor, examiner, or court may interpret claim boundaries years after filing.
Understanding Patent Definiteness Under 35 U.S.C. § 112(b)
Under 35 U.S.C. § 112(b), a patent specification must conclude with one or more claims that particularly point out and distinctly claim the subject matter regarded as the invention. In practical terms, this means that patent claims cannot be so vague that a person of ordinary skill in the art cannot determine what falls within the scope of the patent.
The Supreme Court addressed this requirement in Nautilus, Inc. v. Biosig Instruments, Inc., explaining that a patent claim is invalid for indefiniteness if, when read in light of the specification and prosecution history, it fails to inform those skilled in the art about the scope of the invention with reasonable certainty.
This standard does not require mathematical precision. Patent claims frequently involve complex technologies where exact boundaries are impossible or impractical. For example, courts have recognized that terms such as:
“substantially”
“approximately”
“essentially”
“high purity”
“effective amount”
may be acceptable when the specification provides sufficient context. The issue is not whether a claim uses flexible language, but rather that the flexibility has boundaries.
Technical Background: Why Chemical Patent Claims Often Use Flexible Language
Chemical and materials science inventions frequently rely on numerical values, concentrations, reaction conditions, and performance characteristics. Unlike many mechanical inventions, where dimensions can often be measured directly, chemical processes may vary depending on numerous factors, including:
Raw material purity
Measurement techniques
Environmental conditions
Reaction scale
Analytical instrumentation
Manufacturing variability
Because of this variability, patent claims often use terms of approximation. For example, a chemical process might require:
A temperature of “about 100°C”
A composition containing “about 5% by weight” of an ingredient.
A pH range of “about 3.0 to about 4.0”
The purpose of these terms is understandable. A patent applicant typically does not want a competitor to avoid infringement simply by changing an operating condition by an insignificant amount. However, flexibility introduces risk.
If the patent specification does not explain what degree of variation is acceptable, a court may conclude that the claim fails to provide the public with reasonable notice of what falls within (and outside) the scope of the claimed invention. Balancing flexibility with legal certainty lies at the heart of many patent drafting decisions, and that tension ultimately became the central issue in Enviro Tech Chemical Services.
The Enviro Tech Patent Dispute: Antimicrobial Chemistry, Claim Scope, and the Meaning of “About”
The dispute between Enviro Tech Chemical Services and Safe Foods Corporation involved a relatively narrow legal question with broad implications for chemical patent drafting: when does the use of a flexible term like “about” provide sufficient certainty, and when does it leave the boundaries of a patent claim unclear?
At the center of the dispute was patented technology involving antimicrobial treatment methods for poultry and other food products using peracetic acid-based antimicrobial compositions. These types of chemical formulations are widely used in industrial sanitation applications, including food processing environments where controlling microorganisms is critical for product safety and regulatory compliance.
Enviro Tech’s patented technology involved antimicrobial treatments operating under specific chemical conditions, including defined pH parameters. In antimicrobial chemistry, pH can significantly influence the effectiveness and stability of disinfecting agents. As a result, the claimed pH range was not merely a manufacturing detail, it was an important limitation defining the patented process. The asserted claims recited antimicrobial treatment methods requiring a specified pH range that was defined using the term "about," making the scope of the claimed range central to the dispute.
For chemical inventions, this type of language is common. Patent applicants frequently use terms such as “about,” “approximately,” or “substantially” because chemical processes often involve natural variation caused by measurement techniques, raw material differences, manufacturing conditions, and other practical considerations.
The dispute was not whether the word "about" could ever be used in a patent claim. Courts have long recognized that terms of approximation may be appropriate, particularly in chemical and pharmaceutical technologies. Instead, the question was whether the patent provided enough guidance for a person of ordinary skill in the art to determine the scope of the claimed pH range with reasonable certainty.
The dispute arose after Enviro Tech accused Safe Foods Corporation of infringing claims of Enviro Tech’s patent. Safe Foods challenged the validity of the asserted claims, arguing that the claims were indefinite under 35 U.S.C. § 112(b) because the term “about” lacked a reasonably certain meaning in the context of the claimed invention.
Enviro Tech argued that a person of ordinary skill in the art would understand the meaning of “about” based on the patent specification and the understanding of a person of ordinary skill in the art. Safe Foods disagreed, arguing that the patent did not provide an objective basis for determining how much variation the claimed range allowed.
The district court agreed with Safe Foods and found the asserted claims indefinite. Enviro Tech then appealed the decision to the U.S. Court of Appeals for the Federal Circuit. The Federal Circuit affirmed the district court’s decision, explaining that the term “about” is not inherently indefinite. Patent law permits the use of approximate language when the intrinsic evidence provides sufficient guidance regarding the intended scope of the claim. However, the court emphasized that terms of degree must be tied to an objective standard. That standard may come from sources such as:
The patent specification
The prosecution history
Known industry standards
Experimental data
The technical understanding of skilled artisans
The Federal Circuit concluded that the problem in Enviro Tech Chemical Services was not the use of the word “about” itself. Rather, the problem was that the patent failed to provide sufficient guidance regarding the permissible variation. Without an objective anchor, a skilled artisan could not determine the scope of the claimed invention with reasonable certainty, making the claims indefinite under Section 112(b).
Why the Federal Circuit Found the Claim Indefinite
The Federal Circuit's analysis centered on a fundamental principle of patent law: a patent must provide the public with reasonable notice of where the inventor's exclusive rights begin and end.
Patent claims do more than describe an invention, they legally define the scope of the inventor's exclusive rights. If a person of ordinary skill in the art cannot reasonably determine whether a particular product or process falls within the scope of a claim, the patent fails to provide the public notice required by 35 U.S.C. § 112(b).
In Enviro Tech Chemical Services, the Federal Circuit did not hold that chemical patents cannot use approximate terms such as "about." On the contrary, the court reaffirmed that terms of approximation are not inherently indefinite. Whether such language satisfies the definiteness requirement depends on the context of the patent and whether the intrinsic evidence provides an objective standard for interpreting the claim.
To answer that question, the court examined the intrinsic evidence, including the patent claims, the specification, and the prosecution history, to determine whether a person of ordinary skill in the art could understand the scope of the claimed pH range with reasonable certainty. Although the specification described the invention and its operation, the Federal Circuit concluded that it did not provide sufficient guidance for determining what variation the term "about" permitted in the context of the claimed pH range.
As a result, the court determined that the claims lacked the objective boundaries necessary to inform a person of ordinary skill in the art of their scope with reasonable certainty. Without that objective guidance, the claims failed to satisfy the definiteness requirement of Section 112(b).
The Federal Circuit's reasoning reinforces an important principle of patent drafting: flexible claim language is not inherently problematic, but that flexibility must be supported by objective guidance that allows skilled artisans to understand the scope of the claimed invention. The lesson from Enviro Tech Chemical Services is not that approximate language should be avoided, but that it must be used carefully and supported by the patent's disclosure.
The Importance of Objective Boundaries in Patent Claims
The Federal Circuit's decision builds upon decades of precedent addressing terms of degree (claim language that intentionally allows for some flexibility rather than requiring absolute precision).
Patent applicants frequently use terms such as "about," "approximately," or "substantially" because exact numerical values are not always practical or scientifically meaningful. For example, a pharmaceutical formulation may require "substantially pure" ingredients, a polymer may have a molecular weight of "approximately" a particular value, or a manufacturing process may operate at "about" a specific temperature. Courts have long recognized that this type of language can be appropriate, particularly in chemical and life science inventions where natural variability is common.
The challenge, however, is ensuring that this flexibility has objective boundaries. While there is no single way to accomplish this, patent applicants can strengthen the definiteness of their claims by providing objective guidance within the patent itself. Examples include:
1. A Defined Range in the Specification: One of the strongest ways to support terms such as “about” is to explain the intended scope directly. For example, a specification may state: “As used herein, ‘about 100 °C’ refers to temperatures between approximately 95 °C and 105 °C.” While not every invention requires such explicit definitions, providing numerical guidance can significantly reduce later uncertainty.
2. Experimental Data Demonstrating Acceptable Variation: Technical evidence can also establish boundaries. For example, if testing demonstrates that antimicrobial performance remains effective between pH 3.2 and pH 3.8, the specification can provide evidence supporting the intended meaning of a claimed range. This is especially important in chemical inventions because performance often changes gradually rather than abruptly.
3. Industry Standards or Scientific Conventions: Some terms have recognized meanings within a particular field. For example, a term describing pharmaceutical purity, particle size distribution, or analytical measurement may have accepted industry interpretations. However, applicants should not assume that courts will automatically recognize such meanings. If a term is important to claim scope, the patent should explain why the term has a particular interpretation.
How Enviro Tech Chemical Services Fits Within Prior Federal Circuit Decisions
The Federal Circuit’s decision is consistent with previous cases addressing terms of degree.
Nautilus, Inc. v. Biosig Instruments, Inc.
In Nautilus, the Supreme Court rejected the Federal Circuit's former "insolubly ambiguous" standard and established the modern reasonable-certainty test for indefiniteness.
Under that standard, the question is not whether a person of ordinary skill in the art could eventually determine claim scope through extensive investigation. Rather, the question is whether the claims, read in light of the specification and prosecution history, inform a person of ordinary skill in the art of the invention's scope with reasonable certainty. The Federal Circuit applied this same framework in Enviro Tech Chemical Services, examining whether the intrinsic evidence provided an objective basis for understanding the scope of the claimed pH range.
Interval Licensing LLC v. AOL, Inc.
In Interval Licensing, the Federal Circuit considered claims containing the phrase "in an unobtrusive manner." The court concluded that the claims were indefinite because the patent failed to provide objective boundaries for determining what qualified as "unobtrusive." The lesson was similar to Enviro Tech Chemical Services: terms of degree or subjective language may become indefinite when the patent does not provide sufficient objective guidance for a person of ordinary skill in the art to determine their scope.
Ortho-McNeil Pharmaceutical, Inc. v. Caraco Pharmaceutical Laboratories, Ltd.
The Federal Circuit has also recognized that terms such as "about" can satisfy the definiteness requirement when used in an appropriate context. In Ortho-McNeil, the court concluded that the use of "about" did not render the claims indefinite because, when read in light of the patent's disclosure and the understanding of a person of ordinary skill in the art, the scope of the claims could be determined with reasonable certainty.
Taken together, these decisions demonstrate that the validity of approximate claim language depends not on the words themselves, but on whether the patent provides sufficient objective guidance for a person of ordinary skill in the art to understand the scope of the claimed invention. Enviro Tech Chemical Services follows this same line of precedent, reinforcing that flexibility in claim language is permissible only when it is accompanied by reasonably certain boundaries.
Practical Patent Drafting Lessons from Enviro Tech Chemical Services
The Federal Circuit's decision in Enviro Tech Chemical Services offers several practical lessons for inventors, companies, and patent practitioners. Although the case arose from a dispute over antimicrobial treatment methods, its broader message applies to patent drafting across many technical fields, particularly those involving numerical ranges, process parameters, and terms of approximation.
1. Do Not Assume Common Patent Language Is Automatically Safe
Patent applicants frequently rely on familiar claim language. Many terms may appear throughout issued patents and published patent applications such as:
"about"
"approximately"
"substantially"
"essentially"
"effective amount"
"high"
"low"
"reduced”
"improved"
However, widespread use does not guarantee that a particular term will withstand later scrutiny. Whether a term of degree satisfies the definiteness requirement depends on the context of the invention and whether the patent provides sufficient objective guidance regarding its meaning.
2. Carefully Support Important Numerical Terms During Patent Drafting
For chemical, pharmaceutical, biotechnology, and materials science inventions, numerical values often define critical aspects of the invention and may ultimately determine the scope of infringement. When appropriate, applicants should consider including information such as:
Explicit definitions of important terms.
Representative numerical ranges.
Alternative embodiments.
Measurement methods or testing protocols.
Analytical techniques.
Examples demonstrating acceptable variation.
For example, if a claim recites "a temperature of about 150 °C," the specification may benefit from explaining:
Why that temperature is significant to the invention.
Whether the invention performs similarly over a broader operating range.
How a person of ordinary skill in the art would understand the intended scope of "about" in that context.
Not every invention requires this level of detail, but where a numerical limitation is central to the invention, additional guidance may strengthen the patent and reduce later uncertainty.
3. Include Technical Support for Claim Scope
Patent applications are often drafted with examination before the U.S. Patent and Trademark Office in mind. However, years later, the same patent may be scrutinized during licensing negotiations, due diligence, or litigation. A specification that merely states a desired result may not provide enough support if claim scope is later challenged. Depending on the invention, useful supporting disclosure may include:
Comparative examples.
Experimental results.
Performance testing.
Manufacturing examples.
Tables, figures, or graphs illustrating the claimed operating range.
Although not legally required in every application, this type of technical disclosure can provide valuable context when courts evaluate the meaning and scope of disputed claim language.
4. Draft Claims with Future Readers in Mind
One useful drafting exercise is to ask: If a competitor wanted to design around this patent, would they understand where the claimed boundary begins and ends? If the answer is unclear, the claim language (or the supporting disclosure) may benefit from further refinement. Patent claims should strike a careful balance between providing commercially meaningful protection and giving the public reasonable notice of the scope of the inventor's exclusive rights. Achieving that balance often determines how valuable a patent will be years after it is issued.
The Federal Circuit's decision in Enviro Tech Chemical Services highlights one of the central challenges of patent drafting: protecting innovation while providing clear notice of the boundaries of the claimed invention. Inventors naturally seek broad patent protection, while competitors and the public need reasonably clear notice of what falls within the scope of those rights. Patent law requires both.
Importantly, the decision does not suggest that terms such as "about," "approximately," or "substantially" should be avoided. Rather, it reinforces a longstanding principle of patent law: flexible claim language is most effective when it is supported by objective guidance that allows a person of ordinary skill in the art to understand the scope of the claimed invention with reasonable certainty. A well-drafted patent does more than describe an innovation. It defines the legal boundaries of that innovation in a way that can withstand examination, support licensing efforts, and, if necessary, survive the scrutiny of future litigation.
If you’re interested in learning more about this topic or how the principles discussed in this article may impact your business, don’t hesitate to contact us at info@patentxl.com or at +1(610)871-2024.
