Pressure systems are among the most hazardous equipment found in UK workplaces. A failure — whether a boiler explosion, a ruptured air receiver, or a burst pipeline — can cause fatal injuries, severe burns, and catastrophic property damage. That is why the Pressure Systems Safety Regulations 2000 (PSSR) impose strict inspection requirements on anyone who owns, operates, or is responsible for pressure systems at work.
One of the most common questions businesses ask is: how often does a PSSR inspection need to happen? The answer is not as simple as a fixed interval — and understanding why is important for staying compliant.
What Is a PSSR Inspection?
A PSSR inspection is a thorough examination of a pressure system (or part of a pressure system) carried out by a competent person. The purpose is to verify that the system is safe to continue operating and to identify any deterioration, defects, or conditions that could lead to danger.
The regulations apply to a wide range of equipment:
- Steam boilers and steam systems
- Hot water boilers above 110°C
- Compressed air systems and air receivers
- Autoclaves and sterilisers
- Refrigeration systems operating above specified thresholds
- Pressurised pipework and associated safety devices
- Gas-loaded hydraulic accumulators
- Pressure cookers and digesters used in food processing
If a system contains a relevant fluid (steam, compressed gas, or pressurised liquid that would become gas if released) at a pressure greater than 0.5 bar above atmospheric, PSSR is likely to apply.
The Written Scheme of Examination
Unlike some other statutory inspection regimes (such as LOLER, which has fixed maximum intervals), PSSR does not prescribe a single interval for all equipment. Instead, it requires a Written Scheme of Examination (WSE).
The WSE is a formal document that:
- Identifies the parts of the pressure system that need to be examined
- Specifies the nature of the examination required (visual, non-destructive testing, pressure testing, etc.)
- Sets the intervals at which each examination must take place
- Is prepared or certified by a competent person
The WSE must be in place before the pressure system is operated. It is not optional — operating a pressure system without a valid WSE is a breach of the regulations.
What Determines the Inspection Interval?
The competent person who prepares the WSE will set inspection intervals based on several factors:
Equipment type and design
Different types of pressure equipment have different degradation profiles. A steel air receiver in a clean, dry environment will deteriorate more slowly than a steam boiler in a corrosive industrial setting.
Operating conditions
Temperature, pressure, cycling frequency, and the nature of the fluid all affect how quickly a system degrades. Higher temperatures and pressures generally mean shorter intervals.
Age and condition
As equipment ages, the risk of failure typically increases. A competent person may shorten intervals as equipment approaches the end of its expected design life or if previous examinations have revealed deterioration trends.
Maintenance history
Well-maintained systems with a clear service history may justify longer intervals. Systems with a history of repairs, modifications, or incidents may require more frequent examination.
Consequence of failure
Where a failure could affect a large number of people or cause disproportionate damage, the competent person may specify more conservative intervals.
Typical PSSR Inspection Frequencies
While intervals are set case by case through the WSE, the following are commonly seen in UK workplaces:
| Equipment Type | Typical Examination Interval |
|---|---|
| Steam boilers | 14 months (in-service) / 26 months (out-of-service, cold) |
| Hot water boilers (>110°C) | 14 months |
| Air receivers (simple) | 24–48 months (depending on condition) |
| Compressed air pipework | 48–60 months (depending on WSE) |
| Autoclaves / sterilisers | 14 months |
| Refrigeration systems | 24–60 months (depending on refrigerant and conditions) |
| Safety valves and protective devices | 12–14 months (often aligned with the main system) |
Important: These are indicative ranges only. Your actual intervals will be determined by the competent person who prepares your Written Scheme of Examination. Never assume a generic interval applies to your system.
Who Can Prepare the Written Scheme?
The WSE must be prepared or certified by a competent person. In practice, this is almost always an independent inspection body — often the same body that will carry out the thorough examinations.
Many UK inspection bodies are accredited by the United Kingdom Accreditation Service (UKAS) for pressure systems examination. UKAS accreditation provides assurance that the inspection body has been independently assessed for technical competence, impartiality, and quality management.
What Happens During a PSSR Examination?
During a thorough examination under PSSR, the competent person will:
- Carry out a visual inspection of the system — checking for corrosion, erosion, cracking, leakage, and other signs of deterioration
- Inspect safety devices — safety valves, pressure relief devices, low-water cutouts, and alarms
- Review the system's maintenance records and any repairs or modifications since the last examination
- Conduct non-destructive testing (NDT) where specified in the WSE — ultrasonic thickness testing, magnetic particle inspection, or dye penetrant testing
- Issue a written report detailing the findings, any defects, and whether the system is safe to continue in service
If a defect is found that could give rise to imminent danger, the competent person must notify the enforcing authority (usually the HSE) and the system must be taken out of service.
What If You Miss an Examination?
Operating a pressure system beyond the date specified in the WSE is a breach of PSSR. The consequences can include:
- Enforcement action by the HSE — improvement or prohibition notices
- Insurance implications — many engineering insurance policies are linked to the WSE; missing an examination may invalidate cover
- Fines and prosecution — for serious or repeated breaches
- Civil liability — if an incident occurs while the system is operating beyond its examination date
Frequently Asked Questions
Does PSSR apply to my compressed air system?
If your system includes an air receiver or operates above 0.5 bar gauge pressure, PSSR is very likely to apply. Even relatively small workshop compressors with air receivers fall within scope.
Do I need a WSE for a new system?
Yes. A WSE must be in place before the system is first used. For new installations, the competent person should prepare or certify the WSE as part of the commissioning process.
Can I extend the interval between examinations?
Only the competent person who prepared (or is maintaining) the WSE can change the interval. If your system has a consistently good examination record and operating conditions are stable, the competent person may agree to extend the interval — but this is their professional judgement, not yours.
What is the difference between a PSSR examination and routine maintenance?
A thorough examination under PSSR is a formal, independent safety assessment. Routine maintenance (servicing, replacing wear parts, cleaning) keeps the system running but does not replace the statutory examination. Both are required.
Does PSSR apply to domestic boilers?
Generally, no. PSSR applies to systems used at work. Domestic heating systems in private dwellings are outside scope. However, if a boiler is in a workplace (including a landlord's property used by tenants), it may fall within PSSR depending on the system type and operating parameters.
Compare PSSR Inspection Providers
PSSR examination prices vary considerably depending on the system type, complexity, and provider. Obtaining multiple quotes is the best way to ensure you are paying a fair price for a competent examination.
Compare Engineering is a UK comparison platform for statutory engineering inspections, including PSSR. Request and compare quotes from qualified providers at compareengineering.com.
This article is for general guidance only and does not constitute legal advice. Always consult a competent person or legal adviser for advice specific to your circumstances.