The medical compressed air supply source — what PN-EN ISO 7396-1 requires, point by point
2026-08-08 · Małgorzata Dopierała, Damian Czyczyro, Przemysław Kostera
In brief. A medical compressed air supply system according to the standard PN-EN ISO 7396-1:2016-07 requires at least three supply sources, two independent purification trains and buffer vessels in the G → H → I sequence. The purity of medical air corresponds to class 2 according to ISO 8573-1:2010 (Table 2). The reserve cylinders stand outside the compressor plant — this is a fire-protection requirement. “Shall” in the text of the standard means a requirement, not a recommendation.
A medical compressed air plant room is not a boiler room with a better filter. PN-EN ISO 7396-1:2016-07 describes its structure as a requirement, not as good practice — and most site disputes arise because someone read „shall" as „it is worth doing".
"Should" in the standard means "shall" — and that is the starting point
In the Polish versions of the European Standards the word “should” is a translation of the English shall and expresses a mandatory requirement. It is neither a suggestion nor a recommendation.
The distinction has three levels and determines what may be negotiated in the project:
- "shall" = shall — a requirement. The element is to be applied.
- "may" = may — authorisation to work. An option to choose.
- "should" = should — recommendation.
- NOTES and informative annexes contain no requirements — they describe typical solutions.
The consequence is practical: if the contractor argues that „the standard only recommends two dryers", it is worth checking whether he is referring to a normative clause or to a NOTE.
Three supply sources, not two
The medical compressed air supply source shall have at least three supply sources, including at least one compressor unit — clause 5.5.2.5, requirement (shall).
In addition there is a capacity condition that is often overlooked in sizing: the design flow must be ensured with any two supply sources out of operation. Not with one. With two.
The supply system itself may be a cylinder system (5.3), a compressor system (5.5.2), a system with a mixing unit (5.5.3) or a combination of these — clause 5.5.1.1.
Two purification systems are a requirement, not an option
If at least two supply sources are compressor units, at least two purification systems must be provided — clause 5.5.2.5, requirement (shall).
In a typical hospital compressor plant room with two or three compressor units, the use of two dryers together with the remaining equipment of the purification system is therefore mandatory. This is not raising the standard above the norm, nor a „premium solution" — it is meeting a requirement.
The standard adds a servicing condition: with two or more purification systems it shall be possible to maintain their components separately (5.5.2.9), and directly downstream of the purification systems a sampling point with a shut-off valve shall be provided (5.5.2.10).
Receivers downstream of the dryers — sequence G → H → I
Installation of the receivers downstream of purification systems is an arrangement mapped directly onto the diagrams of Annex A of the standard. In Figures A.5–A.10 the receiver (designation I per Table A.2) is consistently placed downstream of the purification system (designation H), in the flow sequence compressor unit (G) → purification system (H) → receiver (I).
This is the reference solution, not an option permitted by way of exception. The configuration with two dryers analysed in practice corresponds to NOTE 2 (b) or (c) to clause 5.5.2.5 and to Figures A.7 and A.9.
The receivers themselves are to comply with EN 286-1 (or equivalent national standards) and be fitted with shut-off valves, automatic drainage of the liquid phase, a pressure gauge and a pressure relief valve — clauses 5.5.2.7 and 5.5.2.8, requirement (shall).
Complete compressor room equipment — mandatory requirements
Below, only provisions having the character of a requirement (shall). The items described in the NOTES (the typical make-up of the compressor unit and of the purification system) are informative in nature and have deliberately not been listed here.
| Element | Requirement | Standard clause |
|---|---|---|
| Air intake with inlet filter | Located where contamination is minimal; protected against insects, contaminants and water, taking the prevailing wind directions into account | 5.5.2.12 |
| Compressor units | At least three supply sources, including at least one compressor unit; design flow with two sources out of operation | 5.5.2.5 |
| Non-return and shut-off valves of each compressor | Prevention of back-flow through shut-down units; isolation from the pipeline and from the remaining compressors | 5.5.2.5 |
| Overheating protection | Protection of each compressor and measures against toxic compounds entering the pipeline | 5.5.2.5 |
| Two purification systems | With at least two supply sources with compressor units; the ability to service components separately | 5.5.2.5, 5.5.2.9 |
| Solid particle cleanliness | Compliance with ISO 8573-1:2010, Table 2, class 2 — with evidence of conformity from the manufacturer | 5.5.2.2 |
| Dew point sensor with alarm | Connected to the pipeline downstream of all purification systems | 5.5.2.5 |
| CO sensor with alarm system | At least one, on the pipeline downstream of all purification systems | 5.5.2.5 |
| Receivers | Compliant with EN 286-1; shut-off valves, automatic drainage of the liquid phase, pressure gauge, relief valve; separate maintenance of each receiver | 5.5.2.7, 5.5.2.8 |
| Sampling point | With a shut-off valve, directly downstream of the purification system(s) | 5.5.2.10 |
| Two pressure regulators | Permanently installed; each provides the full design flow | 5.5.2.13 |
| Compressor control system | Failure of one compressor without affecting the others; continuity of supply in the event of a control system failure | 5.5.2.11 |
| Anti-vibration measures | Preventing the transmission of vibration between the compressors and the pipeline | 5.5.2.14 |
| Emergency electrical power supply | All compressors connected to the emergency power supply | 5.5.1.5 |
| Fire detection installation | In supply system rooms | 5.8.2 |
| Condensate drainage | Compressors fitted with water drainage systems | 5.8.2 |
| Monitoring and alarm systems | Operating alarms and emergency operating alarms; design in accordance with IEC 60601-1-8 | chapter 6 |
The reserve must stand outside the compressor room — and this is a fire safety requirement
The standard distinguishes three roles in the definitions of clause 3: primary supply source supplies the pipeline under normal conditions (3.51), secondary supply source takes over the supply when the primary source is exhausted or fails (3.58), and reserve supply source supplies the pipeline in the event of failure or depletion both the primary and the secondary (3.54).
The very construction of these definitions gives the reserve its function as the last line of continuity — it is to operate precisely when both other supply sources have failed, including as a result of an event affecting the rooms in which those sources are housed.
The standard translates this directly into a location requirement: the location of the reserve supply sources shall allow access to them and their use in the event of a fire inside the rooms of the primary and secondary sources — clause 5.2.3 item d). The reserve must therefore stand outside the compressor room area.
This is complemented by the requirements of clause 5.8: a cylinder supply source must not be located in the same room as equipment with electric motors — among which the standard expressly counts air compressors (5.8.1 lit. a) — nor with equipment having an open flame source (5.8.1 lit. b). The NOTE to 5.8.1 further indicates that national regulations may require compressors to be located in separate plant rooms.
What ISO 7396-1 does not cover, yet still applies
Pressure vessels have their own conformity route, independent of ISO 7396-1. Vessels manufactured to EN 286-1 are subject in the EU to Directive 2014/29/UE (simple pressure vessels), while vessels with parameters beyond its scope fall under directive 2014/68/UE (PED). In Poland they are subject to technical supervision UDT. The classification of a specific vessel is confirmed on the basis of its documentation, not on the basis of its type.
In addition, the standard refers to: ISO 8573-1:2010 (solid particle purity), IEC 60601-1-8 (alarm systems) and ISO 14971 (risk management, clause 5.2.3).
Frequently asked questions
Are two dryers mandatory in every compressor room?
They are mandatory wherever at least two supply sources are compressor units — and that is the typical hospital configuration. Basis: clause 5.5.2.5, requirement (shall).
Can the receiver be installed upstream of the dryer?
The Annex A diagrams consistently show the sequence G → H → I, i.e. the receiver downstream of the purification system, and the NOTE to pkt 5.5.2.8 refers to the position of the receiver. A decision for a specific installation requires reference to its design documentation.
May the cylinder reserve be located in the compressor room?
No. A cylinder supply source may not be located in a room containing equipment fitted with electric motors, and the standard counts air compressors among them — pkt 5.8.1 lit. a). Independently of this, pkt 5.2.3 lit. d) requires access to the reserve in the event of a fire in the rooms housing the primary and secondary supply sources.
Basis
- PN-EN ISO 7396-1:2016-07 — Clause 3 (definitions 3.51, 3.54, 3.58), clauses 5.1, 5.2.3–5.2.5, 5.5.1, 5.5.2, 5.8, Clause 6, Annex A (Tables A.1 and A.2, Figures A.5–A.10), Annex I
- EN 286-1 — simple pressure vessels (air/nitrogen), cited in clause 5.5.2.7
- ISO 8573-1:2010, Table 2, class 2 — cited in the NOTE to clause 5.5.2.2
- IEC 60601-1-8 — alarm systems, referenced in Clause 6
- ISO 14971 — risk management, referenced in clause 5.2.3
- Directives 2014/29/UE (SPVD) and 2014/68/UE (PED) and national technical inspection legislation (UDT)
This article is based on a technical opinion “Required structure of the medical compressed air supply source according to PN-EN ISO 7396-1:2016-07” by Damiana Czyczyro — Director for medical gas installations at INMED S.A., a member KT 284 PKN. References to clauses of the standard are given after that publication; we do not quote the text of the standard itself — it is available solely under a PKN licence.
A broader treatment of the operation, acceptance and documentation of medical gas installations is provided in the guide „Medical gases in practice. Volume 1" (GMWP) developed by INMED S.A. — order the GMWP guide.
A complete, certified medical compressed air supply system is available here: in.AIR medical compressed air supply systems.
See also: medical gas installations for hospitals, audits of medical gas installations.
Prepared by: the technical team of Małgorzata Dopierała, Damian Czyczyro and Przemysław Kostera — Medpipe Sp. z o.o., design, audits and inspections of medical gas installations. This article is based on the guide „Gazy medyczne w praktyce. Zeszyt 1” (Medical Gases in Practice, GMWP), INMED S.A.