The U.S. Court of Appeals for the Federal Circuit‘s May 4 decision in Enviro Tech Chemical Services Inc. v. Safe Foods Corp. highlights how approximation language in patent claims may affect not only litigation outcomes, but also business decisions involving portfolio value, competitive positioning and prosecution strategy.[1]
The decision does not appear to prohibit the use of terms such as “about” or “approximately.” Rather, it reinforces that such terms may be acceptable where the patent record provides sufficient context for understanding the scope of the claimed range.
At the same time, the case illustrates that approximation language may create risk when the specification, examples and prosecution history do not provide a consistent and objective basis for determining the boundaries of the claim.
In that regard, the decision may serve as a reminder that flexible claim language should be supported by technical context that helps explain with precision what degree of variation is intended.
This article explores why approximation language may be more than a drafting issue and may affect patent validity, value, design around strategies, prosecution decisions and long-term claim strength.
Business Considerations: Risk, Revenue and Patent Asset Value
For companies, the use of approximation language or other terms of degree may affect how patent assets are valued and managed. Patent portfolios are evaluated based on the commercial importance of the covered technology, the breadth of the claims, and the likelihood that the claims will remain enforceable if challenged.
Where key claims rely on terms such as “about” without definitional support or consistent technical examples, uncertainty may arise regarding whether such claims would survive litigation.
That uncertainty may be particularly relevant in mergers and acquisitions, licensing negotiations and financing transactions. A patent portfolio may appear valuable when claim language seems broad enough to cover multiple commercial embodiments.
However, if the breadth depends on an undefined approximation term that lacks a bright-line boundary, the value of that protection may become less predictable. In due diligence, an acquiring company or investor may look not only at whether the patent is issued, but also at whether the claims are sufficiently stable to support future enforcement or licensing revenue.
Approximation language may also affect competitive intelligence and freedom-to-operate analysis. If a competitor’s patent uses “about” near an important numerical boundary, a business may need to assess whether that boundary is supported by the specification and prosecution history. In some cases, undefined approximation language may create uncertainty for patent owners and competitors.
For example, the patent owner may want broad protection, but unclear approximation language can create a risk that the claim is narrowed or invalidated. At the same time, competitors may not know whether operating near the numerical boundary infringes the claim.
This issue may be especially important where a product can be adjusted to operate near, but not clearly within, a claimed numerical limitation. A company evaluating a design-around may analyze whether the patent clearly explains how much variation is covered by the term “about.”
For example, if the specification, testing data, or prosecution history leaves the boundary unclear, the competitor may have a stronger basis to argue that the patent does not provide predictable exclusionary coverage. In that sense, the decision may encourage businesses to evaluate approximation language not simply as a drafting choice, but as a factor in competitive positioning.
The decision also illustrates the cost of flexible drafting. Broad claim language may preserve room to capture variations of a commercial product and may support a larger licensing or damages theory.
However, broad language that lacks objective support may create vulnerability in litigation. A narrower claim with a strict numerical boundary may provide less reach, but may also provide greater stability. Businesses and counsel may therefore consider whether the potential revenue associated with broader claim scope justifies the risk that the claim could later be found indefinite.
This trade-off may be particularly important for patent portfolios used as business assets. A claim that appears commercially powerful because of its flexible language may become less valuable if the same flexibility creates uncertainty regarding enforceability. In this regard, claim breadth and claim durability may need to be considered together, rather than treated as separate issues.
Implications for Patent Counsel
For patent counsel, Enviro Tech may reinforce the importance of consistency across the specification, prosecution history and litigation positions. Approximation terms may be useful, but they may require careful management from the initial drafting stage through enforcement.
One practical lesson involves the risk of extensive specifications that include multiple examples, data sets or experimental results without clear explanation. Detailed technical disclosures often strengthen a patent application by showing support for the claimed invention.
However, when different examples suggest different tolerances, such examples may later be used to argue that the claim boundary is unclear. In Enviro Tech, the specification included examples that could be read as supporting a 0.3 pH deviation, but other examples reflected larger deviations. The court treated that inconsistency in the range of deviation as part of the indefiniteness problem.
That concern does not mean that applicants should avoid including experimental data. Rather, counsel may need to make sure that examples and data sets are organized and explained in a manner that provides consistent signals regarding claim scope.
If different experiments involve different tolerances, the specification may need to explain why such differences exist and whether they relate to measurement error, operating conditions, preferred embodiments or nonlimiting examples.
Prosecution history presents a related concern. During examination, applicants often distinguish prior art by emphasizing specific numerical features. However, statements made to obtain allowance may later affect how the claim is interpreted in litigation. If an applicant argues that a range is narrow or materially different from the prior art during prosecution, the applicant may face difficulty later arguing that “about” provides broad latitude during enforcement.
The concern is not only whether prosecution history estoppel applies, but also whether inconsistent prosecution statements make the claim scope less clear. Where counsel treats an approximation term as narrow or significant in one context but flexible or less important in another, a court may view the record as failing to provide reliable guidance. In Enviro Tech, the Federal Circuit noted the inconsistent treatment of “about” during prosecution and the lack of explanation regarding the intended scope of that term.
The decision may also increase attention to how a person of ordinary skill in the art would understand approximation language. The meaning of “about” may vary depending on the technology. A small pH change may have a different technical significance than a small temperature change, voltage change, concentration change or dimensional variation.
This ambiguity points toward indefiniteness. Counsel may therefore consider building a record that explains the relevant tolerance in the specific technical field, or simply describe a broad range but with precise boundaries that would cover whatever would otherwise have been intended by the use of “about” or other similar language.
In some cases, expert declarations during prosecution may help establish how a skilled artisan would understand an approximation term. Such evidence may be useful where the term is tied to industry standards, measurement techniques, accepted error ranges or known operating tolerances.
While not every application requires expert evidence, technical support from a skilled artisan perspective may be particularly valuable when the claim boundary is close to the prior art or when the commercial value of the claim depends on the breadth of an approximation term.
Practical Considerations for Drafting and Litigation
From a drafting perspective, one approach may be to define approximation terms expressly in the specification. Instead of leaving “about” open-ended, the specification may state that “about” refers to a particular percentage variation, numerical deviation, measurement tolerance or industry recognized margin.
For example, depending on the technology, the specification may define “about” as a variation of 5%, 10% or a specific numerical deviation from the stated value. The definition should align with the technology and the disclosed embodiments, rather than serve as a generic placeholder.
Such definitional language may help provide an objective anchor for claim scope. It may also assist future licensing, due diligence and enforcement analysis by making the boundary easier to evaluate. However, the definition should be drafted carefully because an overly rigid definition may reduce flexibility, while an overly broad definition may create prior art or written description issues.
Applicants may also consider tiered claiming strategies. An independent claim may use approximation language to preserve broader protection, while dependent claims may recite more precise numerical limits. This approach may create a safety net if the broader approximation language is later challenged.
For example, if an independent claim recites “about” a numerical range, dependent claims may recite narrower ranges, fixed endpoints or specific tolerances supported by the specification.
Experimental consistency may also be important. When a patent application includes lab results, testing conditions or commercial trials, the data should be reviewed for consistency with the intended claim scope.
If one experiment suggests an acceptable deviation of 0.3 and another suggests an acceptable deviation of 0.5, the specification may need to explain whether both deviations fall within the intended scope and why. Without such explanation, a later court may view the record as giving inconsistent guidance.
Counsel may also avoid using approximation terms as floating modifiers. A term such as “about” may be less vulnerable when tied to a disclosed tolerance, measurement method, industry practice or technical rationale. By contrast, “about” may create more risk when the patent provides no objective way to determine the permissible deviation. In drafting, the question may be: What would a skilled artisan use to determine where the claimed range begins and ends?
Litigation strategy may require similar discipline. A patentee asserting a claim with approximation language may need to identify a consistent theory for the term early in the case. That theory should be supported by the claim language, specification, prosecution history and technical evidence. If the patentee relies on different meanings of “about” for validity, infringement and prior art avoidance, the inconsistency may create vulnerability.
Conclusion
The Federal Circuit’s decision in Enviro Tech may be viewed as a reminder that approximation language in patent claims remains useful, but not self-defining. Words such as “about” and “approximately” may provide flexibility in technical fields where exact numerical boundaries do not reflect real-world operation. However, the effectiveness of that flexibility may depend on whether the specification and prosecution history provide clear guidance regarding the intended scope of the claimed range.
For businesses, the decision may affect how patents using approximation language are valued, licensed and evaluated during freedom-to-operate analysis. Broad claim language may support greater commercial reach, but only if the record provides enough stability to withstand later challenge.
For patent counsel, the decision may reinforce the importance of drafting definitions, maintaining consistency across examples, perhaps avoiding terms of degree altogether, and aligning prosecution arguments with future enforcement positions.
At a broader level, the case reflects a familiar tension in patent practice: Claims need enough flexibility to capture commercially meaningful variations, but enough precision to provide reliable notice of their boundaries. Approximation terms may continue to serve an important role in that balance, provided the specification and prosecution history give such terms a clear technical foundation.
[1] Enviro Tech Chemical Services, Inc. v. Safe Foods Corp. , No. 24-2160 (Fed. Cir. May 4, 2026).
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