Compressed air is so familiar in workshops, garages and manufacturing sites that its stored energy can disappear into the background. The compressor may receive regular servicing and the receiver may look sound, yet the business can still be missing the document and examination required before a qualifying pressure system is operated. This guide explains how a written scheme of examination works, where responsibility sits and what managers should check.
Start by identifying the pressure system and its safe limits
The Pressure Systems Safety Regulations 2000 (PSSR) are intended to prevent serious injury from stored energy released when a pressure system or one of its components fails. They apply to pressure systems used at work where the relevant definitions and scope are met—not simply to equipment that has the word ‘pressure’ on its label.
A relevant fluid includes steam at any pressure; compressed or liquefied gas, including air, above 0.5 bar gauge; pressurised hot water above 110°C; and gas dissolved under pressure in a solvent. Hydraulic oil is not treated as a relevant fluid for this purpose, although hydraulic equipment still needs suitable controls under other health and safety law.
The user or owner must know the system's safe operating limits, principally pressure and temperature. Start with the manufacturer’s information, installation records, receiver plate, safety-device settings and any alteration history. If the limits, system boundary or equipment identity are uncertain, do not invent them from the gauge reading—obtain competent technical advice.
HSE: Pressure Systems Safety Regulations 2000 ↗ · Pressure Systems Safety Regulations 2000 ↗
Decide whether a written scheme is required
HSE says a suitable written scheme of examination must be in place before qualifying pressure equipment is used, and the equipment must then be examined in accordance with that scheme. For a compressed-air receiver, HSE gives the familiar example of pressure in bar multiplied by internal capacity in litres being equal to or greater than 250 bar litres. A 500-litre receiver operating at 10 bar produces 5,000 bar litres and is well above that example threshold.
Do not turn 250 bar litres into a universal shortcut. Steam systems can require a scheme at any pressure, and scope depends on the relevant fluid, system configuration, possible release of stored energy and statutory exceptions. HSE also lists examples such as steam boilers and autoclaves, certain refrigeration systems, gas-loaded accumulators and fixed LPG installations.
Some systems are exempt or unlikely to require a scheme, including vehicle tyres and certain small portable air receivers. That does not mean they can be ignored. PUWER, manufacturer instructions, risk assessment, maintenance and other specific legislation may still apply. Record how the scope decision was reached rather than relying on an assumption that the equipment is ‘too small’ or ‘only air’.
HSE: Written schemes of examination (INDG178) ↗ · Related guide: PUWER inspection requirements →
The written scheme is the examination plan—not a service certificate
A written scheme identifies the system and the parts requiring examination, the nature of each examination, the preparatory work and safety measures, the maximum interval between examinations, and any critical parts that must be examined after specified repairs or modifications. It should also identify the competent person who certified it and the certification date.
The scheme should cover the parts whose failure could unintentionally release pressure and cause injury. Depending on the system, that can include the receiver, pipework and protective devices such as safety valves. HSE notes that the compressor associated with an air receiver does not normally need to be included merely because it creates the pressure. The competent person should determine the appropriate scope for the actual installation.
Routine servicing and statutory examination have different purposes. A service may replace filters, change oil, drain condensate or check performance. Examination under the written scheme considers the safety-related items and produces the statutory report. One cannot be assumed to satisfy the other, even when the same engineering company provides both services.
Check the equipment, scheme and reports as one system.
HR + SAFETY can help North East employers identify pressure-system gaps, organise the right specialist input and track the resulting actions.
Discuss a pressure-system compliance reviewChoose a competent person for the system—not just the appointment
The user of an installed system, or owner of a mobile system, remains responsible for defining the system and ensuring an appropriate written scheme exists. They may obtain advice and ask a competent person to draw up the scheme, but outsourcing the task does not remove the dutyholder's responsibility.
Competence must match the complexity and hazards of the equipment. HSE describes the necessary breadth of knowledge, experience and independence. An in-house competent person must be sufficiently independent from the operating function and have authority to stop the equipment. For many SMEs, an independent inspection body is the practical route, but the business should still check that the provider's competence covers its particular system.
The scheme must remain suitable throughout the equipment's life. Changes in use, duty, location, connected pipework, protective devices, repairs, modifications, deterioration or age may require review. Adding a receiver or increasing operating pressure should never be treated as a maintenance detail without checking its effect on the scheme and safe limits.
Examine to the scheme and act on the report
PSSR does not provide one default examination interval for every pressure system. The maximum interval and examination nature are set in the written scheme by reference to the equipment and risk. Copying a common industry interval into the diary is not a substitute for reading the certified scheme.
After examination, the competent person provides a written report. The user or owner should check the equipment identified, the date, the findings, the next examination date and any repairs or conditions. If the competent person identifies imminent danger, the equipment must not continue in service as though the report were an advisory quotation. Isolate it, prevent use and complete the required action through competent people.
Maintain the system so it remains safe, operate it within its limits and give operators suitable instructions. Examination is a periodic safeguard, not permission to ignore corrosion, leaks, damaged pipework, malfunctioning drains, unusual cycling, interference with safety valves or other signs of deterioration between visits.
PSSR regulation 9: examination in accordance with the scheme ↗ · PSSR regulation 10: action in case of imminent danger ↗
Pressure-system compliance checklist
Legal requirements and HSE guidance were checked on 23 September 2026. The 250 bar-litre example is particularly relevant to compressed-air receivers; it is not a universal threshold for every kind of pressure system.
- List installed and mobile pressure equipment at every site.
- Record the fluid, maximum pressure, capacity, safe limits and system boundary.
- Check the statutory definitions and exceptions rather than relying on equipment size alone.
- Confirm every qualifying system has a suitable certified written scheme before use.
- Check the scheme identifies examinable parts, methods, preparation and maximum intervals.
- Appoint a competent person with knowledge, experience and independence appropriate to the system.
- Diarise examinations from the scheme and retain the reports where they are accessible.
- Close out defects and stop equipment where an imminent danger is identified.
- Keep servicing and preventive maintenance in place between statutory examinations.
- Review the scheme after relevant changes, repairs, deterioration or altered operating conditions.
A service sticker does not establish PSSR compliance. Identify the system, know its safe limits, confirm whether a written scheme is required, appoint a suitable competent person, examine to the scheme and act on every safety-critical finding.
This guide provides general information for UK employers. It is not legal advice and should not replace advice based on the facts of a specific matter.