Table of Contents
What Are the Pressure Systems Safety Regulations?
The Pressure Systems Safety Regulations 2000 (PSSR) are UK law. They apply to any workplace that operates a pressure system, and that includes almost every compressed air installation in the country. The regulations sit under the Health and Safety at Work etc. Act 1974 and are enforced by the Health and Safety Executive (HSE).
PSSR replaced the earlier Pressure Systems and Transportable Gas Containers Regulations 1989. The purpose is straightforward: to prevent serious injury from the uncontrolled release of stored energy in pressure systems. Compressed air receivers, pipework, and associated fittings all store energy under pressure. If a vessel fails catastrophically, the consequences can be fatal.
The regulations require that pressure systems are properly designed, manufactured, maintained, and periodically examined by a Competent Person. They also require a Written Scheme of Examination (WSE) to be in place before any system is operated.
We advise sensibly. We do not provide legal advice. Always consult the relevant regulations and your appointed Competent Person.
Who Has Duties Under PSSR?
PSSR places legal duties on several parties. Understanding who carries responsibility is critical, particularly for multi-site operators where accountability can become unclear.
The user of the installed system has the primary duty. In most cases, this is the business operating the premises where the compressed air system is located. The user must ensure that:
- A Written Scheme of Examination is in place before the system is operated
- The system is examined in accordance with the Written Scheme
- The system is not operated if there are defects that pose a danger
- Adequate maintenance is carried out
- Records of examinations are kept and are available for inspection
The owner of a mobile system (such as a portable compressor or a hire unit) carries similar duties to the user of an installed system.
The employer has general duties under the Health and Safety at Work Act. Where the employer is also the user, these duties overlap. Where a landlord owns the system but a tenant uses it, both parties may share duties, and this must be clarified contractually.
Designers, manufacturers, importers, and suppliers must ensure that any pressure system they provide is properly designed, manufactured from suitable materials, and supplied with adequate information for safe operation.
For national operators running 5, 10, or 30 sites, the practical challenge is ensuring every location has a current WSE, that examinations are booked and completed on time, and that defects are acted upon. A single missed examination can expose the business to enforcement action.
What Is a Written Scheme of Examination?
The Written Scheme of Examination (WSE) is a document that specifies what parts of the pressure system need to be examined, the nature of each examination, and the maximum intervals between examinations. It must be drawn up or certified by a Competent Person before the system is first operated.
A WSE is not a service report. It is not a maintenance schedule. It is a standalone legal document that defines the examination regime for a specific pressure system at a specific location.
The WSE must include:
- Identification of all protective devices (safety valves, pressure switches, gauges) included in the scheme
- Identification of every part of the system that requires examination
- The nature of each examination (visual, internal, pressure test, NDT)
- The preparation required for each examination (isolation, depressurisation, cleaning)
- The maximum interval between examinations for each item
- The date by which the first examination must be carried out
A common misconception is that the annual insurance inspection covers PSSR compliance. It can, but only if the insurer's engineer is acting as the Competent Person and the WSE is formally in place. Many businesses assume they are compliant because they have an insurance policy when, in reality, no WSE has been drawn up for their specific system.
What Equipment Falls Under PSSR?
The regulations define a pressure system broadly. For compressed air installations, the following items will typically fall within scope:
| Equipment | Typically in Scope | Notes |
|---|---|---|
| Air receivers (vertical and horizontal) | Yes | The most obvious item. Must be examined at intervals defined in the WSE. |
| Compressor pressure vessels | Yes | Oil separators, aftercooler vessels, and integrated receivers. |
| Refrigerant dryer pressure vessels | Yes | Heat exchangers and separators within the dryer. |
| Desiccant dryer vessels | Yes | Twin-tower adsorption dryers contain pressure vessels. |
| Filter housings | Often yes | Depends on size and operating pressure. Many are above the threshold. |
| Distribution pipework | Yes | All pipework carrying compressed air at pressure. |
| Safety valves | Yes | Protective devices are a mandatory part of the WSE. |
| Pressure gauges and switches | Yes | When they form part of the protective system. |
| Condensate drains | Sometimes | Automatic drains with integrated vessels may fall in scope. |
The threshold for PSSR is generally a pressure-volume product (PV) exceeding 250 bar-litres, where the stored gas is above 0.5 bar gauge. In practice, almost any commercial compressed air system exceeds this threshold.
Smaller portable compressors with very small receivers (under approximately 10 litres at standard pressures) may fall below the threshold, but these are rare in commercial or industrial settings.
How Often Must Equipment Be Examined?
The examination intervals are defined by the Competent Person in the WSE. There are no fixed intervals set in the regulations themselves. However, the HSE's Approved Code of Practice (ACoP L122) provides guidance that most Competent Persons follow:
| Equipment Type | Typical Maximum Interval | Notes |
|---|---|---|
| Air receivers (in good condition) | 48 months (written scheme), 24 months (examination) | The WSE review interval and examination interval may differ. |
| Safety valves | 12 months | Functional test or overhaul and reset. |
| Pipework | 48 to 60 months | Depends on material, age, and condition. |
| Protective devices (gauges, switches) | 12 to 24 months | The Competent Person determines the appropriate interval. |
| Older or corroded vessels | Reduced (12 to 24 months) | The Competent Person will shorten intervals where risk is elevated. |
The Competent Person may set shorter intervals if the equipment's condition, operating environment, or history warrants it. Corrosion, external damage, or a history of repairs can all lead to shorter examination cycles. Conversely, a new vessel in a clean, dry environment with good maintenance records may justify longer intervals.
The critical point for site managers is that the due dates are not suggestions. If an examination is overdue, the system should not be operated until the examination is completed. Operating a pressure system outside the requirements of its WSE is a criminal offence.
Choosing a Competent Person
The regulations require that the Competent Person has sufficient practical and theoretical knowledge and experience of the type of system being examined. There is no formal register or mandatory qualification, but in practice, most Competent Persons for compressed air systems are:
- Engineers employed by insurance inspection companies (such as Zurich, Allianz, or HSB)
- Independent inspection engineers with relevant qualifications and experience
- Engineers employed by specialist compressed air companies with appropriate competence
The Competent Person must be sufficiently independent. They should not have a conflict of interest that could compromise the integrity of the examination. For example, the person who services the equipment should not normally be the same person who examines it under PSSR, unless the organisation can demonstrate adequate separation of duties.
When selecting a Competent Person, consider:
- Experience with compressed air systems specifically. A boiler inspector may not have the right expertise for air system pipework and controls.
- Availability to meet your examination schedule. If you have 30 sites, the Competent Person needs the capacity to cover your entire estate within the required intervals.
- Clear reporting. Reports should identify defects, grade their severity, and specify timescales for rectification.
- Willingness to coordinate with your service provider. The Competent Person and the maintenance contractor need to communicate. Defects found during examination need to feed into the maintenance programme.
Common PSSR Non-Compliance Issues
After managing compressed air systems across more than 230 sites, we see the same compliance failures repeatedly. The most common issues are:
No Written Scheme of Examination in place. This is the single most common finding. The business may have an insurance policy, and the insurer may inspect annually, but no formal WSE has been drawn up. Without a WSE, the system is being operated in breach of the regulations from day one.
Overdue examinations. Examination dates slip, particularly when responsibility is distributed across multiple sites. A central facilities team may lose track of due dates, and site-level staff may not realise they are responsible. We regularly find sites where examinations are 6 to 18 months overdue.
Defects not actioned. The Competent Person identifies a defect, issues a report, and then nothing happens. Corroded receivers, seized safety valves, and degraded pipework are left in service because nobody closes the loop between the examination report and the maintenance programme.
Missing or incomplete records. PSSR requires that examination records are kept and available for inspection. If the HSE visits and you cannot produce the WSE and examination reports, you have a compliance problem regardless of whether the examinations were actually done.
Unregistered equipment. New receivers, dryers, or filter assemblies are installed as part of a system upgrade, but nobody updates the WSE to include them. The new equipment operates without being examined.
Safety valves not tested or replaced. Safety valves are the last line of defence against overpressure. They must be tested or replaced at the intervals specified in the WSE. We find seized or incorrectly set safety valves on a regular basis.
Pipework ignored entirely. Many businesses assume PSSR only covers receivers. Distribution pipework is part of the pressure system and must be included in the WSE. Ageing galvanised pipework with internal corrosion is a common and serious risk.
PSSR Checklist for Site Managers
Use this checklist to assess your site's compliance position. If you answer "no" or "unsure" to any item, you may have a compliance gap that needs attention.
- Do you have a Written Scheme of Examination for your compressed air system? You should have a physical or digital copy of the WSE for each site. It should reference the specific equipment at that location.
- Is the WSE current? Check the review date. If the WSE is more than 48 months old, it may need to be reviewed and reissued by the Competent Person.
- Are all pressure vessels, pipework, and protective devices listed in the WSE? Cross-check the WSE against the equipment physically present on site. Look for receivers, dryer vessels, filter housings, and safety valves.
- Are all examinations up to date? Check the last examination date for each item against the maximum interval in the WSE. Flag anything overdue or due within the next 3 months.
- Have all defects from the most recent examination been actioned? Review the Competent Person's report. Every defect should have a corresponding work order showing it has been rectified.
- Are examination reports filed and accessible? The HSE can ask to see these at any time. They should be stored in a known location, ideally digitally for multi-site operators.
- Are safety valves tested or replaced within the required intervals? Check the last test or replacement date against the WSE requirement. Typically this is every 12 months.
- Is there a process for notifying the Competent Person when new equipment is installed? If you add a receiver, change a dryer, or modify the pipework, the WSE must be updated.
- Do you know who your appointed Competent Person is? You should have their name, organisation, and contact details. If you cannot identify them, your WSE may not be valid.
- Is there a responsible person at each site? Someone on site needs to understand that the compressed air system is a pressure system and that examinations must happen on time.
How Airmech Supports PSSR Compliance
We manage PSSR compliance as part of our service contracts for over 230 customer sites across the UK. For national operators running multiple locations, keeping track of Written Schemes, examination dates, and defect rectification across every site is a significant administrative burden. We take that burden off your team.
Here is what we do in practice:
- Asset register: We create and maintain a full register of all pressure system equipment at each of your sites, including receivers, vessels, pipework, and protective devices.
- WSE coordination: We work with your appointed Competent Person (or help you appoint one) to ensure a valid Written Scheme of Examination is in place at every location.
- Examination scheduling: We track due dates and coordinate access for the Competent Person's visits, so nothing falls overdue.
- Defect management: When the Competent Person identifies a defect, we receive the report, quote for the remedial work, and carry it out within the required timescale. You get a closed-loop process from finding to fix.
- Central reporting: Multi-site operators receive a single compliance report covering their entire estate. One document, one view, no gaps.
- HSE inspection support: If the HSE visits one of your sites, we ensure the paperwork is in order and can attend to answer technical questions about the system.
Our clients include Costco (30 UK sites), DPD (5 Midlands hubs), and a range of manufacturing and logistics businesses with complex, multi-site compressed air estates. We have been maintaining compressed air systems for 45 years, and PSSR compliance has been part of that work since the regulations came into force.
If you are unsure about your compliance position, start with our free PSSR Gap Analyser or call us on 02476 345 658 for a straightforward conversation about what needs to happen at your sites.
We advise sensibly. We do not provide legal advice. Always consult the relevant regulations and your appointed Competent Person for decisions specific to your installations.