Gases · CAS Database
Chlorine
Chlorine (CAS 7782-50-5) — Disinfectant and water treatment chemical. Get the SDS and OSHA HazCom guidance you need to store, label, and handle it safely on the job site.
Verified vs OSHA sources · October 5, 2026
CAS Registry Number CAS 7782-50-5 · also known as Cl2, Molecular chlorine
Overview
Disinfectant and water treatment chemical
Chlorine on the job site
Chlorine is handled on site mainly in water-system disinfection and some strong cleaning and treatment products. As a gas it is acutely toxic and corrosive to the airways, with a pungent odor that warns at low levels — the (C) 1 ppm ceiling is easy to exceed near a release. It's heavier than air, so it pools in low spots like pits, trenches, and vaults.
The recurring cause of chlorine injuries is mixing: combining a chlorine product with an acid (or with ammonia) drives off chlorine (or chloramine) gas in a confined space. Never mix cleaning or treatment chemicals, ventilate where you dose or store chlorine, and treat a chlorine smell in a low or enclosed space as a reason to leave and ventilate, not to investigate. Eye and respiratory protection are matched to the task and the potential concentration.
Key takeaways
- Chlorine gas is acutely toxic and heavier than air — it pools in pits, trenches, and vaults.
- Most injuries come from mixing chlorine products with acids or ammonia — never mix chemicals.
- A chlorine smell in a low/enclosed space means leave and ventilate, not investigate.
Field guidance for planning and training — not a substitute for the manufacturer Safety Data Sheet, which controls the exposure limit, PPE, and handling for your specific product.
OSHA Exposure Limits
OSHA permissible exposure limit (PEL) and secondary limit for Chlorine on a US construction site. Where a substance-specific 1926 standard applies, its codified limit is shown; otherwise the figure comes from Table 1 to 29 CFR 1926.55, the construction air-contaminants table. Where 1926.55 does not list the substance, the Safety Data Sheet (Section 8) controls.
| Limit | Value | Basis / citation |
|---|---|---|
| OSHA PEL (ceiling) | (C) 1 ppm | 29 CFR 1910.1000 Table Z-1 |
| Action level | See SDS / standard | Not all substances define an action level |
| Averaging period | ceiling | A ceiling is never averaged: it must not be exceeded at any moment of the shift. Compare with ACGIH TLV / NIOSH REL — often more protective than the OSHA PEL |
This limit is a ceiling. Exposure must at no time exceed it. Where instantaneous monitoring is not feasible, 29 CFR 1926.55(a)(1) lets the employer assess the ceiling as a 15-minute time-weighted average — one that still may not be exceeded at any time during the working day.
This is the general-industry figure. Construction air contaminants are listed separately in Table 1 to 29 CFR 1926.55, and on 33 substances the two differ — sometimes by a wide margin. Where they differ, the construction value governs work on a jobsite.
Many OSHA PELs date to 1971 and may be less protective than current ACGIH/NIOSH values; always check the manufacturer SDS (Section 8) for the controlling limit and engineering-control guidance. Not legal advice.
GHS Classification
Physical Properties
Where Chlorine shows up on the job
Trades that commonly handle Chlorine, each with an OSHA HazCom guide built for the chemicals and tasks on that kind of site:
OSHA & HazCom Compliance Requirements
For construction work, Hazard Communication is governed by 29 CFR 1926.59 (adopts 29 CFR 1910.1200). Employers who use Chlorine must:
- •Maintain an accessible SDS for Chlorine (readily accessible during each work shift, 29 CFR 1910.1200(g)(8))
- •Label all containers with GHS-compliant labels (29 CFR 1910.1200(f)(1) shipped / 29 CFR 1910.1200(f)(6) workplace)
- •Include it in the workplace chemical inventory
- •Train employees on hazards before initial assignment
- •Retain employee exposure and medical records per 29 CFR 1910.1020 — 30-year retention applies to exposure/medical records, not to SDSs generically
HazCom (1910.1200 / construction 1926.59) covers labels, SDSs, and training only — it does not impose chemical storage segregation. Flammable & combustible liquid storage for construction is 29 CFR 1926.152; segregation of incompatibles is planned from SDS Sections 7 and 10. Not legal advice; state-plan states may have stricter rules.
Handling & Secondary-Container Labeling
When you transfer Chlorine into a workplace (secondary) container, OSHA gives two compliant options under 29 CFR 1910.1200(f)(6):
- •(f)(6)(i): full GHS label elements (as on the shipped container)
- •(f)(6)(ii): product identifier + words/pictures/symbols (or combination) that provide AT LEAST general information on the hazards
There is no volume/size cutoff for secondary containers — the ≤100 ml / ≤3 ml accommodations (29 CFR 1910.1200(f)(12) (added by the HCS 2024 final rule)) apply only to the manufacturer's shipped container. A portable container filled for the immediate use of the worker who fills it needs no label (29 CFR 1910.1200(f)(8)).
GHS Hazard Classification under OSHA HCS
OSHA's Hazard Communication Standard adopts the GHS (primarily GHS Revision 7 (HCS 2024)). It requires 8 hazard pictograms (Appendix C, Figure C.1). The Environment pictogram (GHS09) is not required by OSHA — Not in App C; outside OSHA jurisdiction; voluntary.
The 8 OSHA-required pictograms:
For flammable liquids, OSHA classifies by flash point and boiling point (App B.6.1 / 1910.106(a)):
- •Category 1: FP < 73.4°F AND BP <= 95°F
- •Category 2: FP < 73.4°F AND BP > 95°F
- •Category 3: FP >= 73.4°F AND <= 140°F
- •Category 4: FP > 140°F AND <= 199.4°F
The specific GHS classification of Chlorine comes from its Safety Data Sheet (Section 2). Use the live classification panel above and the manufacturer SDS to confirm pictograms and categories.
HCS 2024 Update Deadlines
Under the Hazard Communication Standard 2024 update (aligned primarily GHS Revision 7):
- •May 19, 2026 — manufacturers, importers, and distributors update substance labels & SDSs (1910.1200(j)(2)(i))
- •November 20, 2026 — employers update workplace labeling, the written program & training (1910.1200(j)(2)(ii))
During the interim, parts may comply with the 2012 HCS, the 2024 HCS, or both.
Quick Actions
Put Chlorine on your written inventory, print the workplace label your containers need, and keep your supplier’s sheet reachable on the jobsite.
The safety data sheet for your product comes from the supplier who sold it to you — no public registry can provide it. For the underlying chemistry, the public record is on PubChem.
Where this fits in your HazCom program
- SDS management — collecting the sheet, keeping it current, and making it readable during each work shift.
- GHS labels & workplace labeling — what has to appear on the shipped container, and what a secondary container needs instead.
Free Compliance Tools for Chlorine
Also on a plumbing job
Frequently Asked Questions
What is Chlorine (CAS 7782-50-5)?
Disinfectant and water treatment chemical
What are the OSHA HazCom requirements for Chlorine on a construction site?
For construction work, Hazard Communication is governed by 29 CFR 1926.59 (adopts 29 CFR 1910.1200). Employers who use Chlorine must maintain an accessible Safety Data Sheet (SDS), label containers with GHS-compliant labels, include the chemical in the workplace chemical inventory, and train workers on its hazards before initial assignment.
What is the OSHA permissible exposure limit (PEL) for Chlorine?
OSHA's permissible exposure limit for Chlorine is (C) 1 ppm (ceiling), per 29 CFR 1910.1000 Table Z-1. That figure is the GENERAL-INDUSTRY limit; construction air contaminants are listed separately at 29 CFR 1926.55 Table 1, and where the two differ the construction value governs work on a jobsite. Where the ACGIH TLV or NIOSH REL is more protective, follow the lower value, and confirm the limit for your specific task against Section 8 of the manufacturer Safety Data Sheet.
When does the updated HCS 2024 labeling apply to Chlorine?
Under the Hazard Communication Standard 2024 update (aligned primarily GHS Revision 7), chemical manufacturers, importers, and distributors must update substance labels and SDSs by May 19, 2026, and employers must update workplace labeling, the written program, and training for substances by November 20, 2026. During the interim, parties may comply with the 2012 HCS, the 2024 HCS, or both.
How do I label a secondary (workplace) container of Chlorine?
Under 29 CFR 1910.1200(f)(6) you have two options: (i) the full GHS label elements as on the shipped container, or (ii) the product identifier plus words, pictures, symbols, or a combination that provide at least general hazard information. There is no volume/size cutoff for secondary containers. A portable container filled for the immediate use of the worker who fills it does not require a label (29 CFR 1910.1200(f)(8)).
How long must SDS and exposure records for Chlorine be kept?
Under 29 CFR 1910.1020, 30-year retention applies to employee exposure and medical records (medical records: duration of employment plus 30 years) — not to SDSs generically. Where an SDS is not retained, a record of the chemical's identity, where it was used, and when must be kept for at least 30 years.
Where can I find the SDS for Chlorine?
Under 29 CFR 1910.1200(g)(6) and (g)(7), the manufacturer, importer or distributor that sold you Chlorine must send its Safety Data Sheet with the first shipment, and again with the first shipment after the sheet is updated. HazComFast keeps the sheets you collect in one inventory per jobsite, searchable by product, manufacturer or CAS number, and your jobsite's SDS load onto the phone on their own.
Sources & Primary References
Regulatory data on this page is sourced from HazComFast's verified regulatory module (29 CFR 1926.59 / 1910.1200 and substance-specific 1926 standards), last verified October 5, 2026 against eCFR, OSHA.gov, and the Federal Register. Physical-property data comes from PubChem. Confirm it against the manufacturer Safety Data Sheet. This page is informational and is not legal advice.
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