Pressure Systems Safety — Compressors, Air Receivers and the PSSR Rules (2026)

What PSSR Covers

PSSR applies to systems that contain a "relevant fluid" under pressure. In plain terms, a relevant fluid means compressed or stored gas (including compressed air), steam at any pressure, and pressurised hot water above a certain temperature. If your equipment holds one of these under pressure, you are almost certainly within scope.

For most trades the headline item is the air compressor and its air receiver — the tank that stores compressed air for spray guns, nail guns, tyre inflators, impact wrenches and air tools. But the regulations reach wider than that. Common equipment caught by PSSR includes:

• Air compressors and air receivers — the most common pressure system in garages, body shops, joinery workshops and on plant.
• Steam boilers — including small steam generators and steam cleaning equipment.
• Autoclaves and sterilisers — relevant to some specialist trades and processes.
• Pressurised hot-water and heating systems — sealed systems running above the temperature threshold.

Not everything that holds pressure is in scope. Small portable items and very low-pressure systems can fall outside PSSR — for example, a small portable compressor below the pressure-volume threshold, or a system operating at very low pressure. The pressure multiplied by the internal volume of the vessel is the figure that matters. If you are unsure whether a particular piece of kit is caught, the safe assumption is that it is, and you should have a competent person confirm it rather than guess.

Who Is the Duty Holder?

Under PSSR the main duty falls on the user or owner of the system — usually you, the business that operates the equipment. As duty holder you must make sure the system is properly designed, of suitable construction, correctly installed and properly maintained throughout its life. If you hire equipment in, the responsibilities are shared between the owner and the user, so make sure you understand which party is responsible for examination before you put a hired compressor to work.

The duty holder is also responsible for making sure operators have the information, instruction and training they need to use the system safely, and for keeping the records the regulations require. You cannot delegate the legal responsibility away — even where you bring in a competent person to inspect the kit, the duty to act on what they find stays with you.

The Written Scheme of Examination (WSE)

This is the heart of PSSR, and the part most small businesses miss. For any pressure system containing a relevant fluid above the threshold, you must have a written scheme of examination — a WSE — drawn up or certified by a competent person before the system is used.

The WSE is a document that identifies the parts of the system that need to be examined, sets out the nature of the examination required (including any inspection and testing), and specifies how often each part must be examined. It is the equivalent of the periodic pressure test or inspection schedule for your vessel. A competent person — typically an engineer surveyor, often arranged through your insurer or a specialist inspection company — either writes the scheme or certifies one that has been prepared.

Once you have a WSE in place, the system must then be examined by a competent person in accordance with that scheme before it is used for the first time and at the intervals the scheme specifies thereafter. You must not put the system into use, or keep it in use, unless these examinations have been carried out on time. Letting an examination lapse is one of the most common PSSR failings the HSE finds.

Safe Operating Limits

Every pressure system has safe operating limits — most importantly the maximum pressure it is designed to work at. You must establish these limits and make sure the system is never operated beyond them. In practice that means knowing the rated pressure of your receiver, marking it clearly on or near the vessel, and making sure operators can read and understand it.

Do not be tempted to wind up the cut-out pressure on a compressor to get more out of an air tool, and never bypass or adjust a pressure relief valve to run a system harder. Operating beyond the safe limits is exactly the scenario that leads to a vessel rupturing. The safe operating limits should be clearly marked so that nobody operating the equipment is in any doubt.

Maintenance, Safety Devices and Condensate

Proper maintenance is a legal duty, not a nice-to-have. The two safety devices that matter most on an air receiver are the pressure relief valve (sometimes called a safety valve), which vents excess pressure before it becomes dangerous, and the pressure gauge, which lets the operator see what the system is doing. Both must be fitted, in good working order and maintained. A seized relief valve on an over-pressurised receiver removes the one thing standing between you and an explosion.

Draining condensate is a maintenance task that gets neglected and matters more than people think. Compressing air produces water, which collects in the bottom of the receiver. Left there, it sits against the steel and corrodes the vessel from the inside, thinning the wall until it can no longer safely hold pressure. Drain the receiver regularly through its drain valve, and make condensate draining part of your routine. Internal corrosion from undrained condensate is a leading cause of receiver failure.

Finally, do not modify a pressure system. Welding a repair onto a receiver, fitting a different relief valve, or altering pipework changes the safety case for the whole system and must only ever be done by, or under the direction of, a competent person. An unauthorised modification can invalidate your written scheme and create a vessel that is no longer safe at its marked pressure.

Records and Acting on the Report

You must keep the report of every examination carried out under your written scheme, along with the previous report, until the next examination is done. These records demonstrate the system has been inspected on schedule and are the first thing an HSE inspector or your insurer will ask to see.

The report is not just paperwork to file. When a competent person carries out an examination, they will tell you whether the system can continue in service and may set conditions or a date by which repairs must be made. You have a duty to act on what the report says. If the competent person identifies a defect that means the system poses an imminent danger, they must report it and you must stop using that equipment immediately — you cannot run it until the fault is put right and the system is confirmed safe. Ignoring an examination report is both unlawful and, given what a failed pressure vessel can do, genuinely reckless.

Why This Matters — Stored Energy

It is easy to be casual about a compressor that has run reliably for years, but the danger with pressure systems is the stored energy. Compressed air in a receiver behaves like a coiled spring: if the vessel fails, all that energy is released in an instant. An exploding air receiver or a failed pressure vessel can launch fragments across a workshop, demolish surrounding structure and kill or seriously injure anyone nearby. This is not a theoretical risk — pressure vessel failures have caused fatalities in UK workshops.

That is the reason PSSR exists and the reason the examination regime is mandatory rather than advisory. The cost of a written scheme and periodic inspection is small set against the consequences of a vessel rupturing in an occupied workshop.

Quick Reference: PSSR Duties and Common Equipment

Common Equipment — Is It in Scope?

Use the table as a starting point, not the final word. Whether a specific item is in scope depends on its pressure and volume — confirm borderline cases with a competent person rather than assuming a piece of kit is exempt.

Getting Compliant — A Practical Checklist

• Identify every pressure system in your business — compressors, receivers, steam and pressurised hot-water kit, including hired-in equipment.
• Arrange for a competent person to draw up or certify a written scheme of examination for each in-scope system.
• Have each system examined before use and diary the next examination date from the scheme.
• Mark the safe operating limits clearly and check the pressure gauge and relief valve are present and working.
• Set a routine for draining condensate from receivers.
• Train operators and keep a record that you have done so.
• File examination reports and act promptly on anything they flag.