n-Hexane OSHA PEL checker.

The n-Hexane row in Table Z-1

This is the n-Hexane row of Table Z-1, Limits for Air Contaminants, as the eCFR prints it in 29 CFR 1910.1000. The ppm column is the number to compare a reading against; the mg/m3 column is the same limit expressed by mass.

Reading the footnotes

Four footnotes govern how to read the row. They are printed as follows.

• 1: The PELs are 8-hour TWAs unless otherwise noted; a (C) designation denotes a ceiling limit. They are to be determined from breathing-zone air samples.
• (a): Parts of vapor or gas per million parts of contaminated air by volume at 25 °C and 760 torr.
• (b): Milligrams of substance per cubic meter of air. When entry is in this column only, the value is exact; when listed with a ppm entry, it is approximate.
• (c): The CAS number is for information only. Enforcement is based on the substance name. For an entry covering more than one metal compound, measured as the metal, the CAS number for the metal is given—not CAS numbers for the individual compounds.

For this row, the ppm figure is a volume ratio at 25 °C and 760 torr. The mg/m3 figure is only an approximate conversion of it, so compare readings against the ppm column when you have the choice. The substance name, not the CAS number, is what enforcement is based on.

Why this entry is an 8-hour average

Neither number in the n-Hexane row is preceded by (C), so footnote 1 treats it as an 8-hour TWA. Paragraph (a)(2) of the section reads: “An employee's exposure to any substance in Table Z-1, the exposure limit of which is not preceded by a “C”, shall not exceed the 8-hour Time Weighted Average given for that substance in any 8-hour work shift of a 40-hour work week.”

A (C) in front of a value would make it a ceiling under paragraph (a)(1), which says exposure shall at no time exceed the printed limit. That does not apply here, so the comparison is made against the average over the shift.

Skin designation

The Skin designation column for n-Hexane is blank in the eCFR table.

Worked example

These readings are invented, to show the paragraph (d)(1) arithmetic. One employee's shift has two hours at 750 ppm, two hours at 375 ppm and four hours at 250 ppm of n-Hexane.

E = (2 × 750 + 2 × 375 + 4 × 250) ÷ 8 = 406.25 ppm. Each period is weighted by its length, then the total is divided by the 8 hours of the shift.

The printed limit is 500 ppm, so 406.25 ppm is below it. The highest period is above the printed number, but the comparison uses the shift average, not the peak. The example shows only how the comparison is computed; it does not say the exposure is safe.

The CFR works the same arithmetic in its own Substance A example for a 100 ppm limit, which comes to 81.25 ppm.

Computation formulae in paragraph (d)

Paragraph (d)(1)(i) gives the cumulative exposure formula for an 8-hour shift: E = (Ca Ta + Cb Tb + . . .Cn Tn) ÷ 8, where E is the equivalent exposure for the working shift, C is the concentration during any period of time T where the concentration remains constant, and T is the duration in hours of the exposure at the concentration C. The value of E shall not exceed the 8-hour time weighted average specified in subpart Z of 29 CFR part 1910 for the substance involved.

Paragraph (d)(2)(i) gives the formula for mixtures: In case of a mixture of air contaminants an employer shall compute the equivalent exposure as follows: Em = (C1 ÷ L1 + C2 ÷ L2) + . . .(Cn ÷ Ln), where C is the concentration of a particular contaminant and L is the exposure limit for that substance specified in subpart Z of 29 CFR part 1910. The value of Em shall not exceed unity (1). The paragraph introducing these formulae applies them to substances for which 8-hour time weighted averages are listed.

What paragraph (e) says about controls

This page does not recommend any exposure-control measure. For reference, paragraph (e) of the section is printed as follows: “To achieve compliance with paragraphs (a) through (d) of this section, administrative or engineering controls must first be determined and implemented whenever feasible. When such controls are not feasible to achieve full compliance, protective equipment or any other protective measures shall be used to keep the exposure of employees to air contaminants within the limits prescribed in this section. Any equipment and/or technical measures used for this purpose must be approved for each particular use by a competent industrial hygienist or other technically qualified person. Whenever respirators are used, their use shall comply with 1910.134.”

Limits of this page

This page reads Table Z-1 and the paragraphs of 1910.1000 quoted above. It does not cover Table Z-2 or Table Z-3 substances, other OSHA substance-specific standards, state-plan rules, or recommended limits from other bodies.

A reading below a printed limit is not a statement that the exposure is safe. The page also does not tell you how to sample, how to control exposure or which respirator to use.

The checker compares the one number you type with the printed figure and applies the “shall not exceed” wording as written, so a reading equal to the limit is not above it. For a real workplace, work with a qualified industrial hygienist, your safety data sheet and your area OSHA office. The eCFR lists the newest content version of this section as May 30, 2017.

Sources

Sources opened and read November 12, 2026.

• eCFR: 29 CFR 1910.1000, Air contaminants, Table Z-1 and paragraphs (a), (d) and (e) (text requested as of November 10, 2026; read November 12, 2026)
• eCFR versioner API: version history of 29 CFR 1910.1000 (read November 12, 2026)