Safety data sheet · UN 1006
Argon (Ar) Safety Data Sheet
Argon (Ar, CAS 7440-37-1, UN 1006) is inert, non-toxic and non-flammable, and asphyxiates with no warning. It is about 1.38 times heavier than air, so it collects and persists in pits, trenches, tank bottoms and vessel interiors. This is the hazard that kills welders.
- UN number (compressed)
- UN 1006
- UN number (refrigerated liquid)
- UN 1951
- CAS number
- 7440-37-1
- Atomic weight
- 39.948
- Vapour density (air = 1)
- ≈1.38
- Product
- Argon, compressed
- CAS number
- 7440-37-1
- UN number
- UN 1006
- Transport class
- 2.2 — Non-flammable, non-toxic gas
- Specification
- IS 5760
- Revision
- 1 · 6 August 2026
Also known as: Ar · Liquid argon when refrigerated · LAR
Section 1 — Identification
Product name: Argon, compressed Chemical symbol: Ar CAS number: 7440-37-1 · EC number: 231-147-0 · UN number: UN 1006 Specification: IS 5760
Identified uses: Shielding gas for TIG and MIG welding; root purging; heat treatment and brazing atmospheres; metal degassing; carrier and plasma gas in analytical instruments. Uses advised against: Ventilation or cooling. Any confined-space use without oxygen monitoring and forced ventilation.
Supplier: The Kamrup Industrial Gases Limited.
Section 2 — Hazards identification
GHS classification: Gases under pressure — compressed gas (refrigerated liquefied gas for the liquid product).
Signal word: WARNING
Hazard statements
- H280 — Contains gas under pressure; may explode if heated.
- (Refrigerated liquid) H281 — Contains refrigerated gas; may cause cryogenic burns or injury.
The hazard the classification does not capture. Argon is chemically inert and carries no health-hazard classification, which is precisely why it is underestimated. It asphyxiates without warning, and because it is about 1.38 times heavier than air it collects in low places and persists there.
Pits, trenches, tank bottoms, vessel interiors, ship double-bottoms and inspection chambers are where argon kills people.
Section 3 — Composition
| Component | CAS | Concentration |
|---|---|---|
| Argon | 7440-37-1 | ≥99.99 % (welding grade, IS 5760); higher grades on request |
Single-substance product.
Section 4 — First aid
Inhalation. Remove to fresh air — but do not enter an oxygen-deficient space without air-supplied breathing apparatus and a standby person outside. Give oxygen if trained. If breathing has stopped, give artificial respiration. Seek immediate medical attention.
Skin contact (liquid or cold gas). Cold burns: flush with copious tepid water, do not rub, do not apply direct heat, cover loosely with a sterile dressing, seek immediate medical attention.
Eye contact (liquid or cold gas). Flush with tepid water for at least 15 minutes and seek immediate medical attention.
Section 5 — Firefighting
Non-flammable; does not support combustion.
Specific hazards. Cylinders exposed to fire may rupture. Cool from a protected position or evacuate. Argon discharged into a confined space during firefighting creates an asphyxiating atmosphere at low level.
Section 6 — Accidental release
Evacuate, paying particular attention to pits, trenches, basements, drains and any low-lying area, where argon will collect and remain. Ventilate at low level — high-level extraction will not clear a dense gas from a pit.
Do not enter to isolate a leak without oxygen monitoring and, where deficiency is possible, air-supplied breathing apparatus.
Section 7 — Handling and storage
Gas. Secure cylinders upright. Open valves slowly. Never use argon for ventilation or cooling. Where argon is used inside a vessel or pit, provide forced ventilation and continuous oxygen monitoring for the duration of the work.
Liquid. Cryogenic gloves, face shield and covered footwear. Only vessels rated for cryogenic service. Never seal liquid argon in a closed container — vaporisation will rupture it.
Storage. Well-ventilated area, ventilated at low level. Never store in a basement or pit. Keep cylinders secured and away from heat.
Section 8 — Exposure controls
Argon has no occupational exposure limit; it is not toxic. The control parameter is oxygen concentration.
19.5 % oxygen is the widely used minimum for safe entry. Measure before entry and monitor continuously throughout, at the working level rather than at the top of the space.
Personal protection: oxygen monitoring and, where deficiency is possible, air-supplied breathing apparatus; cryogenic PPE for liquid; welding eye protection of the correct shade.
Section 9 — Physical and chemical properties
| Property | Value | Source |
|---|---|---|
| Physical state | Gas (compressed) or cryogenic liquid | — |
| Appearance | Colourless | — |
| Odour | Odourless | — |
| Atomic weight | 39.948 | NIST |
| Molecular weight | 39.95 g/mol | NIST |
| Normal boiling point | −185.9 °C (87.28 K) | NIST |
| Triple point | −189.4 °C (83.78 K) at 0.689 bar | NIST |
| Critical temperature | −122.3 °C (150.86 K) | NIST |
| Critical pressure | ≈48.98 bar | NIST |
| Vapour density (air = 1) | ≈1.38 | Calculated |
| Flammability | Non-flammable | — |
| Oxidising properties | None | — |
| Proportion of atmosphere | 0.93 % | Literature |
The 1.38 vapour density is the whole safety case. Argon is materially denser than air. It sinks, it collects, and it stays. Every argon fatality in welding follows from that one number, and no amount of chemical inertness offsets it.
Thermophysical constants from the NIST Chemistry WebBook (public domain). NIST records two critical-pressure figures differing by a factor of ten; ≈48.98 bar is the accepted value. Remaining values are standard literature.
Section 10 — Stability and reactivity
Stable and chemically inert. Argon is a noble gas and does not react under any normal industrial condition — including in a welding arc, which is why it is the preferred shielding gas.
Conditions to avoid: heat; and for the liquid, contact with materials not rated for cryogenic service.
Section 11 — Toxicological information
Not toxic. A simple asphyxiant. Oxygen deficiency causes rapid loss of coordination and judgement followed by unconsciousness, usually without the casualty recognising anything is wrong.
Section 12 — Ecological information
Not classified as environmentally hazardous. Argon is a natural component of air.
Section 13 — Disposal
Vent to atmosphere in a safe, well-ventilated outdoor location, away from pits, drains, basements and building intakes where the dense gas could collect. Return cylinders to the supplier.
Section 14 — Transport
| UN number | UN 1006 (compressed) · UN 1951 (refrigerated liquid) |
| Proper shipping name | ARGON, COMPRESSED |
| Class | 2.2 |
Transport upright and secured, valves closed, caps fitted, in a ventilated vehicle. Never carry cylinders in an enclosed passenger compartment.
Section 15 — Regulatory information
- Gas Cylinders Rules, 2016 (PESO)
- IS 5760 — argon specification
- IS 7285 — seamless steel cylinders
- IS 3224 — cylinder valves
- EN ISO 14175 — argon as a welding shielding gas
- ADR 2025 — UN 1006 / UN 1951
Section 16 — Other information
Revision 1, issued 6 August 2026.
Relates to argon as supplied and does not release the user from assessing their own installation and application. A signed PDF copy is available on request for audit files; this HTML page is the current version.
Argon — frequently asked questions
Why is argon more dangerous in a confined space than nitrogen?
Because it is heavier. Nitrogen is close to the density of air and mixes; argon is about 1.38 times heavier, so it sinks into pits, trenches, tank bottoms and vessel interiors and **stays there**, sometimes for hours after work has stopped. An argon-filled pit looks exactly like an empty one, and ventilation at high level does nothing to clear it.
Will an argon atmosphere give any warning?
None. No smell, no irritation, and no feeling of breathlessness — the urge to breathe responds to carbon dioxide build-up, not oxygen shortage. Collapse can occur within a breath or two, with no sensation that anything is wrong.
Is welding inside a tank with argon shielding safe?
Only with continuous forced ventilation and continuous oxygen monitoring. Argon accumulates inside the vessel exactly where the welder is working, and it displaces air from the bottom upward. This scenario — a welder working inside a vessel with argon shielding — is a recurring cause of fatalities.
How long does argon persist in a pit after work stops?
Longer than most people expect. Because it is denser than air it does not disperse readily on its own, and a still pit can remain hazardous long after the work has finished. Never judge by elapsed time — measure the oxygen concentration.
What are the hazards of liquid argon?
Severe cold burns on contact at −185.9 °C, embrittlement of materials not rated for cryogenic service, and a very large expansion on vaporising, so a small spill can make a room oxygen-deficient quickly. Never seal liquid argon in a closed container.
Does an oxygen meter protect me?
For argon, yes — unlike carbon dioxide, argon harms only by displacing oxygen, so an oxygen monitor is the correct instrument. Use one before and throughout confined-space entry, not just at the start.
Enquiries
Request a quotation
State the gas or equipment, the quantity or capacity, and your location. KIGL will confirm the grade, the cylinder or plant size, and whether the location can be served from Noonmati, or through our agent network.