Guide
Liquid medical oxygen (LMO) in India: the supply chain from air separation plant to hospital bed and how it compares with PSA
Liquid medical oxygen (LMO) is oxygen liquefied at −183 °C in an air separation unit, released under a drug licence against the Indian Pharmacopoeia monograph, carried by cryogenic tanker to a hospital VIE tank and vaporised into the medical gas pipeline. One tonne of LMO gives about 700 m³ of gas at 0 °C.
- Specification
- Indian Pharmacopoeia monograph
- Gas from one tonne of LMO
- About 876 litres of liquid giving about 700 m³ of gas at 0 °C
- 2021 peak demand
- Nearly 9
- 2021 production
- About 5
- Oxygen 93
- PSA medical oxygen grade
Liquid medical oxygen is how a large Indian hospital gets most of its oxygen: made in an air separation plant, carried as a liquid at about −183 °C, stored on site in a vacuum-insulated tank and turned back into gas for the pipeline that runs to every ward. The COVID-19 second wave in April and May 2021 showed the whole country how long and fragile that chain is. This page sets out each link, what governs it, what the 2021 figures showed, and when a hospital should look at on-site PSA instead. The physical properties of the liquid are on liquid oxygen properties and safety.
What makes liquid oxygen "medical"?
Medical oxygen is a drug, regulated under the Drugs and Cosmetics Act 1940 and specified by the Indian Pharmacopoeia (IP) monograph. IS 309:2023, the Indian Standard for industrial oxygen, states in clause 1 that it does not cover oxygen for medical or inhalation purposes. LMO is chemically the same molecule as industrial liquid oxygen. The difference lies in the licence, the dedicated tankers and tanks, batch analysis and release, and the paper trail back from the patient to the plant. Purity alone does not make oxygen medical, as industrial vs medical oxygen explains.
The LMO supply chain, link by link
| Link | Equipment | What governs it |
|---|---|---|
| 1. Production | Cryogenic air separation unit (ASU): air compressed, purified, cooled and distilled; liquid oxygen drawn from the column | Drug manufacturing licence for medical product; IP monograph |
| 2. Transport | Vacuum-insulated cryogenic road tanker; in 2021 also rail tankers on Oxygen Expresses | SMPV (Unfired) Rules 2016, mobile pressure vessels |
| 3. Hospital storage | Static VIE tank on a concrete pad, with pressure-building coil and relief devices | SMPV (Unfired) Rules 2016; AIGA 030/13 storage practice |
| 4. Vaporisation | Ambient-air vaporisers, sized for peak flow and for icing | Supplier design; AIGA 030/13 asks for icing checks |
| 5. Pressure control and reserve | Line regulators, plus cylinder manifolds as secondary and reserve supply | IS/ISO 7396-1:2007 |
| 6. Distribution | Copper medical gas pipeline, zone valves, alarms, terminal units | IS/ISO 7396-1:2007 |
Two numbers make the chain concrete. One tonne of LMO occupies about 876 litres and gives about 700 m³ of gas at 0 °C, from NIST densities. A 46.7 litre medical cylinder filled to 150 bar at 15 °C holds about 10 kg of oxygen, or 7.4 m³ at 15 °C (NIST density 215.6 kg/m³), so a single tonne of liquid replaces about 100 cylinders. That ratio is why bulk liquid became the norm for large hospitals, and why a hospital running on cylinders alone needs a large and well-run cylinder operation.
The VIE needs the same care as any liquid oxygen store. AIGA 030/13, the Asian edition of the EIGA document on cryogenic storage at users' premises, covers tanks from 1,000 to 125,000 litres. It requires a concrete or other non-flammable, non-porous surface under the equipment and for at least 1 m around the tanker fill coupling, because liquid oxygen soaked into tarmac can ignite on impact. Where a changeover valve serves two relief devices, it requires that at least one is always open to the tank at full bore. The container types are compared on cryogenic cylinders, dewars and tanks.
Rules that matter
In a written reply in Parliament in July 2021, the Ministry of Health and Family Welfare set out the scale of the second wave. The figures below are as reported.
| Measure | Figure |
|---|---|
| Peak medical oxygen demand, first wave | 3,095 MT |
| Peak medical oxygen demand, second wave | nearly 9,000 MT |
| Daily LMO production, August 2020 | about 5,700 MT |
| Daily LMO production, 13 May 2021 | 9,690 MT |
| Allocation to states, 28 May 2021 | 10,250 MT |
| LMO tankers available, 15 July 2021 | 1,244, of which 225 added after March 2020 |
| LMO moved by Oxygen Express trains, to 30 June 2021 | 35,500 MT |
| PSA plants sanctioned | 1,222, with 245 commissioned by 20 July 2021 |
Four engineering lessons follow from these figures, without needing any opinion added to them.
Lessons of 2021, in the government's own figures
- Production was not the only limit Output was raised by about 70 % in nine months, yet supply still fell short where it was needed, because liquid oxygen is made in a limited number of large plants and has to be moved, often over long distances.
- Transport is a separate capacity A tanker fleet sized for normal demand cannot be expanded overnight. The government added tankers and moved liquid by rail to cover the distance.
- On-site storage buys time A hospital's VIE size, its reserve cylinders and its vaporiser capacity set how long it can ride out a late delivery.
- Distributed generation was the policy response Sanctioning more than 1,200 on-site PSA plants spread production across hospitals instead of concentrating it at a few ASUs.
PSA or LMO for a hospital?
| Factor | Liquid medical oxygen | On-site PSA plant |
|---|---|---|
| Product | Medical oxygen to the IP monograph, high purity | Oxygen 93: 90 to 96 % oxygen, the balance mostly argon (WHO International Pharmacopoeia, 11th ed. 2022) |
| Stored reserve | Days of supply in the VIE, depending on tank size | None beyond buffer vessel; needs cylinder or liquid back-up |
| Depends on | Deliveries from a distant ASU | Reliable power and maintenance of compressors and sieve |
| Logistics | Tanker access to the site; supplier contract | None for product; spares and service |
| Licensing | SMPV (Unfired) Rules for the tank; licensed supplier | Plant installation and medical-use approvals as applicable |
| Best fit | Large hospitals near supply, with high steady demand | Hospitals far from ASUs, or as a second independent source |
Many hospitals now hold both: a VIE or PSA plant as the primary source and the other, or a cylinder manifold, as the second. The pipeline standard, IS/ISO 7396-1:2007, is built around primary, secondary and reserve sources for exactly this reason. How PSA separates oxygen from air, and why its purity tops out in the mid-nineties, is on how PSA oxygen generation works.
Rules that matter
What a hospital should specify for an LMO installation
- Tank size against delivery risk Size the VIE on peak daily use multiplied by the longest credible gap between deliveries, not on average use.
- Vaporiser capacity for peak flow Ambient-air vaporisers lose capacity as they ice up; specify for the peak hour with icing, and a standby bank.
- An independent second source A cylinder manifold or PSA plant that can carry the critical load if the liquid supply fails.
- Alarms that reach someone Low tank level, low line pressure and changeover alarms repeated to a staffed point, not only on the tank.
- Tanker access A hard standing the tanker can reach and turn on, with the fill coupling on concrete and away from drains.
- A named supplier with a drug licence for the oxygen, and a written delivery commitment.
KIGL's role in the LMO chain
KIGL operates an air separation plant and supplies liquid oxygen. It also designs and installs medical gas pipeline systems, builds PSA oxygen plants for on-site generation, and fills medical oxygen cylinders at its own PESO-approved works at Noonmati, Guwahati, and Howrah, Kolkata, for hospitals' cylinder banks and reserves. The cylinder product is on medical oxygen, and how a pipeline system is laid out is on medical gas pipeline basics.
Liquid medical oxygen — frequently asked questions
What is the full form of LMO?
LMO stands for liquid medical oxygen: oxygen liquefied at about −183 °C in an air separation unit, kept in a vacuum-insulated tank and vaporised back to gas at the point of use. It is the form in which most hospital oxygen travels, because one tonne of LMO yields roughly 700 cubic metres of gas, far more than a tanker of cylinders can carry.
What is liquid medical oxygen?
It is oxygen made by cryogenic air separation, stored and transported as a liquid at about −183 °C, and manufactured and released as a drug under a licence from the drug regulator, against the Indian Pharmacopoeia monograph. Chemically it is the same as industrial liquid oxygen; what makes it medical is the licence, the dedicated equipment, the batch release and traceability to the patient.
How is liquid medical oxygen transported in India?
By vacuum-insulated cryogenic road tanker from the air separation plant to the hospital, where it is transferred into a static VIE tank. Tankers are mobile pressure vessels under the SMPV (Unfired) Rules 2016. In 2021 the Ministry of Health reported 1,244 LMO tankers available by mid-July, 225 of them added after March 2020, and Indian Railways' Oxygen Expresses carried 35,500 MT by 30 June.
How much oxygen gas is in one tonne of LMO?
About 700 m³ at 0 °C and 1 atm, or about 740 m³ at 15 °C, from NIST densities. One tonne occupies about 876 litres as liquid. A typical 46.7 litre cylinder filled to 150 bar holds about 10 kg, or 7.4 m³ at 15 °C, so one tonne of LMO equals the contents of about 100 such cylinders, which is why bulk liquid suits a large hospital and cylinders suit a small one.
Why did India run short of medical oxygen in 2021?
Demand rose faster than distribution could follow. Government figures given to Parliament show production was raised from about 5,700 MT/day in August 2020 to 9,690 MT/day by 13 May 2021, but second-wave demand peaked near 9,000 MT, the plants were concentrated in a few regions, and liquid had to be moved long distances in a limited tanker fleet.
What is a VIE in a hospital?
A vacuum-insulated evaporator: the hospital's bulk liquid oxygen tank. It stores LMO in an inner stainless steel vessel inside an evacuated jacket, holds pressure with a pressure-building coil, and feeds ambient-air vaporisers that turn the liquid into gas for the medical gas pipeline. It needs a concrete base, safety distances, licensing under the SMPV (Unfired) Rules 2016 and a cylinder reserve.
Does a hospital need a licence for an LMO tank?
Yes. A static cryogenic tank is a pressure vessel under the Static and Mobile Pressure Vessels (Unfired) Rules 2016, administered by PESO, so the installation needs PESO approval and licensing before it is filled. The oxygen itself is a drug supplied by a licensed manufacturer. The pipeline downstream is built to IS/ISO 7396-1:2007.
References
- Asia Industrial Gases Association. (2013). Storage of cryogenic air gases at users' premises (reproduced with EIGA permission) (AIGA 030/13). https://asiaiga.org/uploaded_docs/AIGA%20030_13_Storage%20of%20cryogenic%20air%20gases%20at%20users'%20premises.pdf
- Bureau of Indian Standards. (2023). Oxygen, compressed gas and liquid; IS/ISO 7396-1:2007 Medical gas pipeline systems (IS 309:2023, Fifth Revision).
- Linstrom, P. J., & Mallard, W. G. (Eds.). (n.d.). NIST Chemistry WebBook (NIST Standard Reference Database 69). National Institute of Standards and Technology. [oxygen saturation properties] https://webbook.nist.gov/cgi/cbook.cgi?ID=C7782447
- Parliamentary written reply, Ministry of Health and Family Welfare, July 2021, as reported by Deccan Herald (23 July 2021) https://www.deccanherald.com/amp/story/india%2Fmedical-oxygen-demand-peaked-to-nearly-9000-mt-in-2nd-covid-wave-govt-1012079.html
- Static and Mobile Pressure Vessels (Unfired) Rules 2016, Petroleum and Explosives Safety Organisation
- The Global Fund, technical briefing note on PSA oxygen purity (citing the WHO International Pharmacopoeia, 11th edition, 2022)
Enquiries
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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 the agent network.