Odor or pool of liquid at the site visit

The site visit meets a strong odor, or a pool of liquid, inside a building or on the ground outside. The standard makes both things to look for, an odor together with its source, and gives neither a class. Whether there is a recognized environmental condition (REC) depends on four things: what the odor or liquid is, where it comes from, where it is and how far it reaches, and how it measures against the de minimis tests.

What the answer turns on

What it is. A REC needs hazardous substances or petroleum products, and a release, a likely release or a material threat of one (E1527-21, 3.2.73). Observation on the site visit includes what is noticed by smell, and the practice includes no sampling (E1527-21, 3.2.96, 7.4), so identity rests on appearance, smell, labels, safety data sheets and the people asked. The standard's petroleum products include natural gas (E1527-21, 3.2.61). Its appendixes are nonmandatory; the one on non-scope issues gives methane, which occurs naturally or through biological digestion, as an example of a substance that may be taken for a hazardous substance though the federal law does not, or does not yet, define it as one (E1527-21, X6.10). The standard does not say how to tell one from the other at a site. Indoor air quality unrelated to a release into the environment, and mold, are non-scope considerations (E1527-21, 13.1.5.7, 13.1.5.11).
Where it comes from. The site visit items are strong, pungent or noxious odors with their sources, and any standing surface water, pool or sump whose liquid is likely a hazardous substance or petroleum product (E1527-21, 9.4.13, 9.4.14). The appendix on the REC definition gives liquid pooled around a drum storage area, with stressed vegetation, as an observation that could be direct evidence of a release (E1527-21, X4.1). Trace the odor or the liquid to a container, tank, drain, sump, pipe or process (E1527-21, 9.4.11, 9.4.12, 9.4.15, 9.4.21). Where it rises from the ground or through a floor, migration includes vapor in the subsurface (E1527-21, 3.2.53): see vapor in a Phase I. Where the source is a container or tank, ask also whether its condition poses a material threat: an obvious threat, likely to lead to a release, that the professional judges would likely harm public health or the environment (E1527-21, 3.2.52, 3.2.55).
Where it is, and how far it reaches. The legal background appendix reports the federal agency's reading that a release not held wholly inside a building or structure is one into the environment, and that this takes in a spill from a tank or valve onto a concrete pad (E1527-21, X1.1.1.1, footnote 21; X1.1.1.2). The body of the standard does not say how a pool on an interior floor is weighed. Establish where the liquid sits and where it goes: a floor, a crack or drain, soil or pavement, surface water, and how large an area it covers (E1527-21, 9.4.20, 9.4.21, 9.4.23).
How it measures against the de minimis tests. A release that is found is weighed against the de minimis definition, whose tests are that the condition generally poses no threat to health or the environment and generally would not draw enforcement (E1527-21, 3.2.20). In the two staining illustrations of the appendix on the REC definition, the professional's experience of the regulators concerned answers the enforcement test (E1527-21, X4.3). See staining on pavement or soil.

The records that bear on it

Site visit. Odors and their sources, pools and sumps are described in the report, or reported as not found, with photographs of what indicates a REC or a de minimis condition (E1527-21, 9.4, 9.4.13, 9.4.14, 12.3). Rain, flooding and other constraints are noted and documented (E1527-21, 9.2.6).
Interviews and documents. Ask the key site manager or the occupant present what the liquid or odor is, where it comes from and since when (E1527-21, 10.2, 10.5.1). The owner, key site manager and user are asked for safety data sheets, spill prevention, countermeasure and control plans and reports of any cleanup (E1527-21, 10.8.1).
Government records. The required minimum search for federal release reports covers the subject property, and state spill records can be additional records (E1527-21, 8.2.2, Table 2, 8.2.4).

What the federal rule says

The inquiry rule (40 CFR part 312) does not mention odors or pools. On what is found, it says:

Releases and threatened releases identified as part of the all appropriate inquiries should be noted in the report of the inquiries.

40 CFR 312.20(h), edition revised as of July 1, 2025

For a party seeking the liability protections that rule's subject is hazardous substances (40 CFR 312.1(c)(1)); the standard includes petroleum products (E1527-21, 1.1.2). The same paragraph adds that its standards are not intended to require the report to identify quantities of hazardous substances, and of the other substances it names,

that because of said quantities and amounts, generally would not pose a threat to human health or the environment.

40 CFR 312.20(h), edition revised as of July 1, 2025

How it is written up

The odor or pool is a finding when the professional judges it may indicate hazardous substances or petroleum products present or likely present at the subject property (E1527-21, 12.5).

Where the professional concludes a release, or a likely release, has left such substances present or likely present at the subject property, the opinion gives the grounds: what the odor or liquid is taken to be, its source, its extent, the evidence. Unless judged a de minimis condition or a historical REC, the REC is listed in the Conclusions, and the professional should give an opinion on additional investigation, if any (E1527-21, 3.2.20, 3.2.39, 12.7, 12.8).

Where the professional concludes the source poses a material threat of a future release, the opinion names the obvious condition and why a release with likely impact is expected, and the REC is listed in the Conclusions (E1527-21, 3.2.52, 12.6, 12.7).

Where the professional judges both de minimis tests met, the opinion says why, and a de minimis condition need not appear in the Conclusions (E1527-21, 3.2.20, 12.7). Where the professional concludes the odor or liquid is not a hazardous substance or petroleum product, or not a release, the opinion gives its reasoning on the same four facts (E1527-21, 12.6).

A locked room the odor came from may be what could not be observed on the site visit. Required information that good faith efforts could not obtain is a data gap, significant if it affects the ability to identify a REC: named in the Findings with the sources consulted, discussed in the Opinions and listed in the Conclusions (E1527-21, 3.2.19, 3.2.78, 12.5.1, 12.6.2, 12.7).

This page is general reference for environmental professionals. It does not classify any property. ASTM E1527-21 is the standard and is not reproduced here; the judgment of the environmental professional on the facts governs.