Safety data sheet · UN 1046
Helium (He) Safety Data Sheet
Helium (He, CAS 7440-59-7, UN 1046) is inert, non-toxic and non-flammable, and asphyxiates without warning. At 0.165 kg/m³ it is roughly one seventh the density of air, so it rises and collects against ceilings and in roof voids — the opposite of argon, and it defeats floor-level gas detection entirely.
- UN number (compressed)
- UN 1046
- CAS number
- 7440-59-7
- Atomic weight
- 4.003
- Vapour density
- 0.165 kg/m³ at 21.1 °C
- Normal boiling point
- −268.9 °C
- Product
- Helium, compressed
- CAS number
- 7440-59-7
- UN number
- UN 1046
- Transport class
- 2.2 — Non-flammable, non-toxic gas
- Revision
- 1 · 10 August 2026
Also known as: He · Helium-4 · Balloon gas when supplied to that grade
Section 1 — Identification
Product name: Helium, compressed Chemical symbol: He CAS number: 7440-59-7 · EC number: 231-168-5 · UN number: UN 1046
Identified uses: Inert shielding and purging where argon is unsuitable; leak detection by mass spectrometry; carrier gas in gas chromatography; pressurising and purging of process systems; lifting gas; cooling in cryogenic and superconducting service. Uses advised against: Inhalation for voice effect — this has killed people. Any confined-space use without oxygen monitoring at working height and above.
Supplier: The Kamrup Industrial Gases Limited.
Section 2 — Hazards identification
GHS classification: Gases under pressure — compressed gas.
Signal word: WARNING
Hazard statements
- H280 — Contains gas under pressure; may explode if heated.
The hazard the classification does not capture. Helium carries no health-hazard classification and no exposure limit, because it is genuinely inert and genuinely non-toxic. It still asphyxiates without warning, and it does so at the top of the room.
At 0.165 kg/m³ helium is about one seventh the density of air. It rises immediately on release and forms a layer against the ceiling that thickens downward. Roof voids, the tops of tall vessels, mezzanines, stairwell heads and any space with a raised or vaulted ceiling are where a helium atmosphere accumulates — and a person working at height reaches it first.
Section 3 — Composition
| Component | CAS | Concentration |
|---|---|---|
| Helium | 7440-59-7 | >99 % |
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. Rescuer deaths in helium and nitrogen atmospheres consistently outnumber the original casualties. Give oxygen if trained. If breathing has stopped, give artificial respiration. Seek immediate medical attention.
Skin contact (rapidly expanding gas). Frostbite: 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 (rapidly expanding gas). Flush with tepid water for at least 15 minutes and seek immediate medical attention.
Section 5 — Firefighting
Non-flammable; does not support combustion. Helium will not contribute to a fire under any circumstance.
Specific hazards. Cylinders exposed to fire may rupture. Cool from a protected position or evacuate. Helium released into an enclosed space during firefighting creates an asphyxiating layer at high level, where anyone on a ladder or platform will meet it.
Section 6 — Accidental release
Evacuate and ventilate at high level. Extraction at floor level will not clear a gas that has already risen — this is the exact inverse of the response for argon or carbon dioxide, and applying the wrong one wastes the time that matters.
Pay particular attention to roof spaces, ceiling voids, upper floors of stairwells and the head space of tall vessels. Do not enter to isolate a leak without oxygen monitoring at working height and, where deficiency is possible, air-supplied breathing apparatus.
Section 7 — Handling and storage
Gas. Secure cylinders upright. Open valves slowly. Never use helium to ventilate, cool or blow down clothing. Where helium is used inside a vessel or a roofed space, provide forced ventilation drawing from high level and continuous oxygen monitoring at the working position.
Never inhale helium from a cylinder. Cylinder pressure can rupture lung tissue, and the gas displaces oxygen immediately.
Storage. Well-ventilated area with ventilation at high level. Keep cylinders secured, valve caps fitted, away from heat, and below 52 °C.
Section 8 — Exposure controls
Helium 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, at head height and above, not at floor level.
Personal protection: oxygen monitoring positioned for a light gas; air-supplied breathing apparatus where deficiency is possible; gloves and eye protection when making and breaking connections.
Section 9 — Physical and chemical properties
| Property | Value | Source |
|---|---|---|
| Physical state | Gas (compressed) | — |
| Appearance | Colourless | — |
| Odour | Odourless | — |
| Atomic weight | 4.003 | Group technical data |
| Molecular weight | 4.003 g/mol | NIST |
| Normal boiling point | −268.9 °C | Group technical data |
| Critical temperature | −267.9 °C | Group technical data |
| Critical pressure | 33.2 psia (≈2.29 bar) | Group technical data |
| Vapour density | 0.165 kg/m³ at 21.1 °C | Group technical data |
| Specific volume | 96.7 ft³/lb at 21.1 °C, 1 atm | Group technical data |
| Water solubility | Very slightly soluble | Group technical data |
| Flammability | Non-flammable | — |
The density is the whole safety case, and it points upward. Every control for helium — where you ventilate, where you mount the detector, where you expect to find the hazard — is the mirror image of the control for argon. A site that has learned to look down for gas will look in the wrong place for this one.
Constants from group technical data.
Section 10 — Stability and reactivity
Stable. Helium is a noble gas and forms no compounds under any industrial condition. No incompatible materials, no hazardous decomposition products, no polymerisation.
Conditions to avoid: heat above 52 °C, which raises cylinder pressure.
Section 11 — Toxicological information
Not toxic. A simple asphyxiant. Oxygen deficiency causes rapid breathing, reduced alertness, impaired coordination and judgement, fatigue, nausea, unconsciousness and death, in that order and quickly.
A rise in voice pitch is a genuine and unusually useful early indicator, because helium transmits sound faster than air. It is a reason to leave immediately — not a measurement.
Section 12 — Ecological information
Not classified as environmentally hazardous. Helium is a natural, if scarce, component of the atmosphere and escapes to space rather than accumulating.
Section 13 — Disposal
Vent to atmosphere in a safe, well-ventilated outdoor location, clear of building intakes and away from any roofed or overhung area where the rising gas could be trapped. Return cylinders to the supplier.
Section 14 — Transport
| UN number | UN 1046 |
| Proper shipping name | HELIUM, COMPRESSED |
| Class | 2.2 — Non-flammable, non-toxic gas |
| Labels | 2.2 |
Transport upright and secured, valves closed, caps fitted, in a ventilated vehicle. Never carry cylinders in an enclosed passenger compartment — a leak in a car fills it from the roof down.
Section 15 — Regulatory information
- Gas Cylinders Rules, 2016 (PESO)
- IS 7285 — seamless steel cylinders
- IS 3224 — cylinder valves
- ADR 2025 — UN 1046
Section 16 — Other information
Revision 1, issued 10 August 2026.
Relates to helium 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.
Helium — frequently asked questions
Why does helium need different precautions from argon?
Because it goes the other way. Argon is about 1.38 times heavier than air and sinks into pits; helium is roughly a seventh the density of air and **rises**. The same room needs the opposite response — ventilate at high level, monitor at head height and above, and treat ceiling voids, roof spaces and the tops of tall vessels as the danger zone rather than the floor.
Is the voice change a reliable warning?
It is a warning, not a safeguard. Helium carries sound faster than air, so speech rises in pitch in a helium-rich atmosphere — and unlike most asphyxiants that gives you something you can actually notice. But it tells you the atmosphere is already contaminated, and it says nothing about how much oxygen is left. Treat it as a reason to leave, not a reason to measure.
Will a floor-mounted gas detector protect me?
No, and this is the most common mistake with helium. Detection installed for heavier gases sits low and will read normal while a helium layer builds against the ceiling. Oxygen monitoring for helium must be at working height and, in tall or roofed spaces, above it.
Helium is inert. Where does the risk actually come from?
Entirely from displacement and pressure. It will not burn, will not react and will not poison you. It asphyxiates by pushing oxygen out of the space you are breathing in, and a cylinder is a high-pressure vessel that can become a projectile if the valve is damaged.
Can rapidly escaping helium cause cold burns?
Yes. Gas escaping fast from a cylinder or a failed connection cools sharply as it expands, and contact near the point of release can cause frostbite. Helium's boiling point is −268.9 °C, the lowest of any element, so any liquid helium service is a severe cryogenic hazard requiring dedicated equipment and training.
Does helium have an occupational exposure limit?
No. It is not toxic, so there is no exposure limit to work to. The control parameter is oxygen concentration in the breathing zone, measured where the work is done.
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