1910.1000(a): Table Z-1 Air Contaminant Limits
For substances in Table Z-1 with a limit preceded by a "C", an employee's exposure must never exceed that ceiling; if instant monitoring is not feasible, the ceiling is assessed as a 15-minute TWA not to be exceeded at any time during the workday. For other Table Z-1 substances, exposure must not exceed the 8-hour TWA in any 8-hour shift of a 40-hour work week.
Key takeaways
- 1910.1000(a) is part of OSHA's general industry standards (29 CFR Part 1910).
- OSHA cited it 150 times in the last 3 years, in 142 inspections, with $818,102 in current penalties.
- 6 deaths are linked to inspections that cited this rule.
- Most citations: TX (14), WI (14), PA (14).
- Related part: 1910.1000(a)(2) Other substances—8-hour Time Weighted Averages (121 citations).
- Free 5-minute toolbox talk for your crew below.
In this article
What this rule covers
29 CFR 1910.1000(a) ("Table Z-1") is one requirement inside 1910.1000 Air contaminants, an OSHA general industry standard (Part 1910). It includes 2 sub-paragraphs. The official text below is copied word for word from the Electronic Code of Federal Regulations (eCFR). The numbers, injury cases and training on this page show how OSHA enforces it on real job sites.
Official text
(a) Table Z-1 — 150 citations
(1) Substances with limits preceded by “C”—Ceiling Values. An employee's exposure to any substance in Table Z-1, the exposure limit of which is preceded by a “C”, shall at no time exceed the exposure limit given for that substance. If instantaneous monitoring is not feasible, then the ceiling shall be assessed as a 15-minute time weighted average exposure which shall not be exceeded at any time during the working day. Open (a)(1) 10 citations
(2) Other substances—8-hour Time Weighted Averages. 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. Open (a)(2) 121 citations
Source: eCFR, text current as of 2026-10-15. Read all of 1910.1000.
Injuries linked to this rule
6 deaths are linked to inspections where OSHA cited 1910.1000(a).
At 10:43 a.m. on January 23, 2025, Employee #1 working as a laborer for a landscaping service was finishing breakfast while sitting on a zero turn, John Deere mower. A coworker (foreman) found him unresponsive still sitting on the mower. It was determined that the…
Full case list with employer, penalty, filters and download is part of OSHA Data (Purple Belt).
Unlock with Purple BeltWhere and how often it was cited
| Year | Citations |
|---|---|
| 2023 | 11 |
| 2024 | 51 |
| 2025 | 53 |
| 2026 | 35 |
Top states: TX (14), WI (14), PA (14), MN (14), OH (13)
Largest penalties
| Employer | Location | Penalty for this rule |
|---|---|---|
| JOSEPH'S FOOD PRODUCTS COMPANY INC. | BROADVIEW, IL | $50,000 |
| QUVA PHARMA, INC | BLOOMSBURY, NJ | $42,148 |
| CACIQUE FOODS LLC | AMARILLO, TX | $16,550 |
| COMPASS GROUP USA, INC. | SYRACUSE, NY | $16,550 |
| BUILDING INTEGRATED SERVICES, LLC | CHAGRIN FALLS, OH | $16,550 |
Free toolbox talk
A 5-minute crew talk on 1910.1000(a), plus alerts when this rule changes. Free.
OSHA interpretation letters
None exist. OSHA has not published a letter of interpretation for 1910.1000(a).
Related parts of this rule
- 1910.1000(a)(2) Other substances—8-hour Time Weighted Averages 121 citations
- 1910.1000(a)(1) Substances with limits preceded by “C”—Ceiling Values 10 citations
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Frequently asked questions
What does a "C" in Table Z-1 mean?
It is a ceiling value that an employee's exposure shall at no time exceed.
How is a ceiling checked if instant monitoring is not possible?
As a 15-minute time weighted average that shall not be exceeded at any time during the working day.
What about substances without a "C"?
Exposure shall not exceed the 8-hour TWA in any 8-hour work shift of a 40-hour work week.
About this page
Sources
- 29 CFR 1910.1000 (eCFR), text current as of 2026-10-15
- U.S. Department of Labor enforcement data: OSHA inspections, citations and accident records, copied nightly; data as of 2026-10-21
3-year window. Federal OSHA only; state-plan rules are not counted. Plain-language text is a summary, not legal advice; the official text controls. Black Belt Safety is not part of OSHA or the Department of Labor.