OPINION
A federal grand jury indicted George Bryant, Crystal Keel, Scottie Magouirk, and Richard Whited on ten counts relating *297 to the manufacture and use of methamphetamine. Following a jury trial in Bryant’s case and guilty pleas in the cases of Keel, Magouirk, and Whited, the district court imposed sentences of 100, 188, 151, and 151 months in prison, respectively. Whited’s sole challenge relates to whether his arrest in a motel room containing both a minor and an operational methamphetamine laboratory, replete with the smell of methamphetamine chemicals, warranted a six-level enhancement for substantial risk of harm to the life of a minor under the United States Sentencing Guidelines (U.S.S.G.) § 2Dl.l(b)(6)(C) (2005) (now at § 2D 1.1(b)(8)(C) in the 2006 version). For the reasons set forth below, we AFFIRM the judgment of the district court.
I. BACKGROUND
A. Procedural background
The grand jury charged Whited in seven counts of the ten-count indictment that also named Keel, Magouirk, and Whited. In exchange for the government’s dismissal of the six other counts, Whited pled guilty to Count One only. Count One charged him with conspiracy to knowingly manufacture methamphetamine between January of 2001 and April 22, 2004, in violation of 21 U.S.C. §§ 841(a)(1), 841(b)(1)(C), and 846. The Presentence Report (PSR) calculated Whited’s advisory Sentencing Guidelines range to be between 168 and 210 months of imprisonment. This was based on a total offense level of 33, which included a six-level enhancement for substantial risk of harm to the life of a minor pursuant to U.S.S.G. § 2D1.1 (b)(6)(C). In May of 2005, the district court recalculated the range to be between 135 and 168 months based on its disagreement with a separate two-level enhancement recommended by the PSR. The court agreed, however, with the recommended six-level substantial-risk-of-harm enhancement and sentenced Whited to 151 months in prison. This timely appeal followed.
B. Factual background
Although the PSR recites numerous instances of “offense conduct” in support of Whited’s guilty plea and the probation officer’s recommended sentence, only one instance is relevant to this appeal. On October 20, 2003, several police officers arrested Whited and Keel in a room at the Country Inns and Suites motel in Manchester, Tennessee. The arrests followed a search of the room in which the officers found and seized finished methamphetamine product, marijuana, and an operational methamphetamine laboratory. Also in the room was a 17-year-old female named Jessica Gipson, whom the officers arrested as well. Finally, the officers reported smelling chemicals — a “telltale chemical meth smell” — during their search.
II. ANALYSIS
A. Standard of review
We review de novo a district court’s “finding on a mixed question of law and fact — such as the existence of a substantial risk of harm to human life under U.S.S.G. § 2D1.1(b)(5)(B).”
United States v. Davidson,
Although the presence of a minor brings this case within U.S.S.G. § 2Dl.l(b)(6)(C) as opposed to § 2Dl.l(b)(6)(B) (the general provision regarding harm to human life at issue in Davidson), we see no reason why the same analysis should not apply. Comment 20 to § 2D1.1 — titled “Substantial Risk of Harm Associated with the Manufacture of Amphetamine and Methamphetamine” — draws no distinction between the two provisions. If anything, the language of § 2D1.1(b)(6)(C) — addressing “a substantial risk of harm to the life of a minor or an incompetent” — strongly suggests that the required showing for the six-level enhancement should be no more exacting than that required for the three-level enhancement under § 2Dl.l(b)(6)(B), which addresses “human life” more generically.
B. Discussion
Two sections of Whited’s plea agreement are especially relevant to the disposition of his appeal. The first is paragraph 12, which provides in pertinent part:
Defendant acknowledges that his sentence will be determined within the discretion of the Court, as constrained by law. Defendant acknowledges that the Federal Sentencing Guidelines will be considered in defendant’s case to determine the appropriate sentence.
Whited, accordingly, can not and does not question the applicability of U.S.S.G. § 2Dl.l(b)(6)(C) to his case.
The other significant provision is sub-paragraph 18(b), which provides in pertinent part: On or about October 20, 2003, defendant Whited, Keel and a juvenile were arrested in a Manchester motel room at the Country Inns and Suites motel. There was a methamphetamine laboratory, finished methamphetamine, and a loaded handgun, a Czeh 7.65 semi-auto pistol, in the room.
Whited did not dispute these facts at his sentencing hearing and does not dispute them on appeal. His objection at sentencing to the six-level enhancement instead related to his subjective knowledge of the minor’s actual age. As his counsel expressed in writing following her review of the PSR, “Mr. Whited denies knowing the true age of the 17-year-old who was with Crystal Keel. He thought she was Crystal’s age and therefore he objects to this 6 level enhancement.”
This narrow objection necessarily implies that if Whited had known the true age of the 17-year-old minor in his motel room, he would not be contesting the six-level enhancement. As in other related contexts, however, the Guidelines do not require Whited’s actual knowledge of the minor’s age in order to apply the enhancement, and this court has held that “[s]en-tencing guidelines should be read as they are written.”
United States v. Cobb,
*299
Whited raises a slightly different argument on appeal, claiming that the analysis and the result in
Davidson
compel a favorable result in his case. This argument is probably sufficiently distinct from his prior mistake-of-fact claim so as to limit him to plain-error review. We need not resolve the point, however, because Whited cannot prevail under even the more favorable de novo standard. The relevant facts in
Davidson
were that the Davidsons maintained “a methamphetamine lab located in a locked barn loft in a remote location.”
The laboratory was in Dick’s apartment, which itself is in a large apartment complex in a densely settled area near a number of other apartment complexes. Dick’s apartment is within an eight-unit structure. At the time the search warrant was executed — while Defendants manufactured methamphetamine — the other seven units were occupied. An elementary school is housed nearby, and a creek flows through the apartment complex and empties into the Tennessee River.
Id. at 471.
Regarding the substantiality of the risk created by Whited’s methamphetamine-production operation, the risk here is far greater than in
Davidson
and arguably even greater than in
Layne.
Whited, his methamphetamine laboratory, and a 17-year-old girl were all in the same room when and where the arrest took place at the Country Inns and Suites motel. According to travel web sites, the motel is an 81-unit complex. To be sure, nothing in the record indicates the manner of disposal (the second Guidelines’ factor) of the hazardous materials in Whited’s motel room, so we must therefore treat that factor as “indeterminate.”
See Davidson,
Factor 1: Quantity and manner of storage of hazardous materials
Although Whited is generally correct in noting that “definite” factual findings as to the four Guidelines’ factors are “absent in this case,” certain relevant facts are undisputed. One such fact is that Whited’s motel room contained “a smell of chemicals, [a] telltale chemical meth smell.” As
Layne
teaches, many of the chemicals involved in the production of methamphetamine are “toxic,” “inherently dangerous,” “highly flammable,” and “pose a serious risk to those who inhale them.”
Layne,
Factor 3: Duration of the offense and extent of the manufacturing operation
Count One of the indictment, to which Whited pled guilty, describes a period of methamphetamine manufacturing lasting more than three years, from January of 2001 to April of 2004. The arrest of Whited in his motel room occurred on October 20, 2003, well within this time frame. Although we acknowledge that the record does not indicate for how long Whited had been staying in the motel room or for how long he had been maintaining the methamphetamine laboratory found inside, the fact that there was an actual operational laboratory in the room, as opposed to simply finished methamphetamine product, suggests more than an insignificant passage of time. “Thus, like the first factor, this factor does not suggest that the laboratory at issue was extraordinary, but nevertheless militates in favor of application of [§ 2Dl.l(b)(6)(C) ], which was. designed to address the inherent dangers of methamphetamine manufacturing.”
Layne,
Factor 4: Location of the laboratory and the number of lives placed at substantial risk of harm
Whited’s methamphetamine laboratory was in a densely populated area. As noted, the motel room where Whited operated the laboratory was one of 81 units — more than 10 times the number of units in
Layne.
Whited, Keel, and Gipson were all in the room at the time of the arrest. Although the record does not reveal how many of the other 80 rooms in the motel were also occupied, “the laboratory here clearly posed an inhalation risk not only to Defendants and [Gipson], but also to others.”
See Layne,
Even if all 80 of the other rooms in the two-floor motel had been empty at the time (a highly unlikely possibility), the undisputed fact that a minor was physically present in Whited’s room would remain. The wording and legislative history of § 2Dl.l(b)(6)(C) suggest that this fact alone — a single minor — would warrant the six-level enhancement under the circumstances of this case. Unlike § 2D1.1(b)(6)(B), which addresses “a substantial risk of harm to [ ] human life other than a life described in subdivision (C),” § 2D1.1(b)(6)(C) addresses “a substantial risk of harm to the life of a minor or an incompetent.” (Emphasis added.) The added singular articles “a” and “an” might appear to represent only a technical inconsistency with subdivision (B), but the legislative history of § 2D1.1 confirms their special significance. In passing the Methamphetamine and Club Drug Anti-Proliferation Act of 2000, from which § 2D 1.1 derives, the U.S. House of Representatives drew attention to methamphetamine’s potential to harm human life, and “more disturbing,” the lives of children:
The methamphetamine epidemic in America differs in kind from the threat of other illegal drugs because methamphetamine can be made from readily available and legal chemicals and substances, and because it poses serious dangers to both human life and to the environment. Additionally, these chemicals and substances are utilized in a manufacturing process that is unstable, *301 volatile, and highly combustible. Even small amounts of these chemicals, when mixed improperly, can cause explosions and fires. For every one pound of methamphetamine that is produced, approximately five pounds of toxic and often lethal waste products may be left behind at the laboratory site, or disposed of in rivers, kitchen sinks, or sewage systems in an effort to conceal evidence of illegal manufacturing. More disturbing is that most of these laboratories are situated in residences, motels, trailers, and vans, and often times are operated in the presence of children.
Methamphetamine and Club Drug Anti-Proliferation Act of 2000, H.R.Rep. No. 106-878, at 22 (2000) (emphasis added).
To be sure, the
Davidson
court did note that “[njeither the language of [§ 2Dl.l(b) ] nor its commentary suggests that the Substantial-Risk-of-Harm Enhancement should be applied any time methamphetamine is manufactured in anything less than professional laboratory conditions.”
III. CONCLUSION
For all of the reasons set forth above, we AFFIRM the judgment of the district court.