India’s medical oxygen journey has shifted from cylinders to on-site PSA plants. This article explains the technology, purity myths, demand variability, and why smart design defines reliable hospital oxygen systems.
The Evolution of Medical Oxygen Infrastructure in India: From Cylinders to On-Site PSA Oxygen Generation
Abstract
Medical oxygen is a critical therapeutic gas in healthcare delivery. Traditionally, hospitals in India relied on high-pressure cylinders and liquid oxygen (LOX) systems for oxygen supply. Over the last decade, and particularly during the COVID-19 pandemic, on-site oxygen generation using Pressure Swing Adsorption (PSA) technology has emerged as a viable alternative. This paper discusses the evolution of medical oxygen infrastructure in India, explains the working principles of oxygen concentrators and PSA systems, examines prevailing misconceptions regarding oxygen purity, and highlights the technical and economic challenges associated with PSA oxygen generators under variable hospital demand conditions.
Introduction
An oxygen concentrator is a device that extracts oxygen from ambient air by selectively adsorbing nitrogen, thereby delivering an oxygen-enriched gas stream. Such systems are widely used for medical oxygen therapy, especially in environments where liquid oxygen or high-pressure cylinders pose safety, logistical, or economic challenges. Oxygen concentrators are also referred to as oxygen gas generators or oxygen generation plants.
The concept of oxygen concentration for medical use dates back to the early 1970s, when home medical oxygen concentrators were first introduced. Large-scale manufacturing began in the late 1970s, with early development driven by companies such as Union Carbide Corporation and Bendix Corporation. Over time, advancements in adsorption materials and compressor technologies led to the widespread adoption of PSA-based oxygen generators.
Oxygen Generation Technologies
- Oxygen can be produced through two primary technologies:
- Cryogenic air separation, which is suitable for large-scale, high-volume oxygen production.
- Pressure Swing Adsorption (PSA), which is economical and reliable for small to medium-scale applications.
PSA oxygen generators offer several advantages over traditional oxygen supply methods. They eliminate dependence on cylinder logistics, reduce safety risks associated with high-pressure storage, and provide continuous on-site oxygen generation. These systems are used not only in healthcare, but also in pharmaceutical manufacturing, water treatment, glass production, and other industrial applications. PSA technology is particularly valuable in remote or geographically inaccessible regions.
Adoption of PSA Oxygen Technology in India
In India, PSA oxygen generators began gaining acceptance around 2017–2018. Their importance became particularly evident during the COVID-19 pandemic, when disruptions in cylinder and liquid oxygen supply chains exposed the vulnerability of centralized oxygen distribution systems.
Despite this, initial resistance existed within the Indian medical fraternity regarding the clinical acceptability of PSA-generated oxygen, primarily due to concerns about oxygen purity. PSA systems typically deliver oxygen with a purity of approximately 93%, compared to 99% purity from cryogenic or bottled oxygen.
This concern, however, stems from a misunderstanding. In cryogenic oxygen, argon is removed during the separation process, resulting in near-pure oxygen. In PSA oxygen, argon is not separated and constitutes approximately 5% of the product gas, with the remaining balance being trace amounts of nitrogen. Argon is an inert gas and is not harmful for medical use. International pharmacopeia standards (USP, BP, and European Pharmacopoeia) recognize 93% ±3% oxygen as medical grade.
Clinical Use and Oxygen Delivery
In modern clinical practice, oxygen is predominantly delivered to patients through ventilators. Ventilators operate based on the Fraction of Inspired Oxygen (FiO₂), wherein oxygen is mixed with ambient air before being delivered to the patient. As a result, even when the inlet oxygen purity is 93%, the final oxygen concentration delivered to the patient is governed by the FiO₂ setting rather than the source purity alone.
Post-pandemic, with increased awareness of supply chain vulnerabilities and logistical constraints associated with cylinder and LOX systems, PSA oxygen generators have gained wider acceptance among healthcare professionals. This acceptance led to a rapid influx of manufacturers into the PSA oxygen market.
Design Challenges of PSA Oxygen Generators in Hospitals
PSA oxygen generators in hospitals are typically designed based on peak or surge oxygen demand. However, hospital oxygen consumption is inherently variable and depends on several factors, including patient occupancy, ICU load, ventilator usage, and operating theatre activity.
For example, in a 30-bed hospital with a 10-bed ICU and four ventilators (two operational and two standby), oxygen consumption can vary significantly:
When two ventilators are in use, daily consumption may be equivalent to approximately ten jumbo cylinders (7 m³ each).
When ventilators are not in use, consumption may drop to the equivalent of two to four cylinders per day.
Under such conditions, a PSA oxygen generator with a nominal capacity of 4 m³/h is generally sufficient. However, demand fluctuations between 40% and 100% of rated capacity pose a significant technical challenge. Maintaining oxygen purity at low flow rates is difficult in conventional PSA designs. To avoid purity deviations, many systems are forced to operate continuously, irrespective of actual demand.
Economic Implications
Continuous operation of PSA plants significantly impacts operating costs. Consider a 4 m³/h PSA oxygen generator equipped with a 5.5 kW air compressor. Including the dryer and service factors, the total connected load is approximately 7 kW. If operated continuously for 24 hours a day, at an electricity tariff of INR 12 per kWh, the monthly power cost is approximately INR 60,000.
In contrast, if the hospital’s average oxygen consumption is only 60% of the PSA plant’s capacity, the equivalent cylinder usage would be around 180 cylinders per month. At an average cost of INR 250 per cylinder, the monthly expenditure would be approximately INR 45,000.
This cost comparison explains why, despite the conceptual advantages of PSA oxygen generators, many hospitals remain hesitant to adopt them.
Future-Outlook
Given the large number of hospitals in India and the persistent challenges associated with transportation, storage, and logistics of cylinders and liquid oxygen, PSA oxygen generators remain the most practical long-term solution for decentralized medical oxygen supply. However, their success depends heavily on robust design.
Manufacturers must ensure that PSA oxygen generators are engineered to handle wide variations in demand while maintaining oxygen purity under start-stop and partial-load operating conditions. Advanced control strategies, optimized adsorption cycles, and energy-efficient compressors are essential to reduce operational costs and improve economic viability.
Conclusion
PSA oxygen generation technology has evolved into a critical component of India’s medical oxygen infrastructure. While challenges remain, particularly in managing variable demand and operating costs, these issues are primarily design-related rather than conceptual. With appropriate engineering solutions tailored to hospital usage patterns, PSA oxygen generators have a strong and sustainable future in the Indian healthcare ecosystem.
Author: Ashok Seshasayee
Managing Director | Zenox Gas Systems
