Written schemes of examination for heating plant: when PSSR applies and what it covers

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If your commercial site has steam plant, high-temperature hot water, a compressed air receiver or certain other pressurised equipment, the Pressure Systems Safety Regulations 2000 (PSSR) are likely to apply. One of the central duties is to have a written scheme of examination (WSE) in place before the system is used, and to have the system examined by a competent person to that scheme. This guide explains when a written scheme of examination for heating plant is needed, what regulation 8 says it must cover, and what remains the duty holder's job.

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What PSSR is trying to prevent

HSE's Approved Code of Practice L122 says the aim of PSSR is "to prevent serious injury from the hazard of stored energy (pressure) as a result of the failure of a pressure system or one of its component parts." HSE's overview page for the Regulations repeats that the duties relate to pressure systems for use at work and the risk to health and safety. A written scheme of examination is how the user shows the right parts will be examined, at the right intervals, by a competent person, before and during use.

When does a written scheme of examination apply?

PSSR applies to pressure systems that contain, or are likely to contain, a relevant fluid. HSE's PSSR overview lists relevant fluids as:

steam at any pressure;
compressed or liquefied gas, including air, at a pressure greater than 0.5 bar above atmospheric pressure;
pressurised hot water above 110 °C; and
a gas dissolved under pressure in a solvent (acetylene).

HSE also notes that relevant fluids do not include hydraulic oils: hydraulic systems use high pressure but do not store energy in the same way, so they are not covered by PSSR. INDG178 (Written schemes of examination) uses the same definition of relevant fluid and adds that a written scheme is "a document containing information about selected items of plant or equipment which form a pressure system, operate under pressure and contain a 'relevant fluid'."

Many low-temperature hot water (LTHW) heating systems sit below the 110 °C threshold and therefore fall outside the written-scheme requirement. Steam boilers, high-temperature hot water plant, compressed air receivers and some LPG storage systems used for heating are the kinds of plant HSE lists as likely to need a scheme. If you are unsure whether your heating plant contains a relevant fluid, ask a competent person or your insurer's engineering inspector before you assume the duty does not apply.

What regulation 8 requires the scheme to cover

PSSR regulation 8 is clear. The user of an installed system (or the owner of a mobile system) must not operate it, or allow it to be operated, unless there is a written scheme for the periodic examination, by a competent person, of:

all protective devices;
every pressure vessel and every pipeline in which a defect may give rise to danger; and
those parts of the pipework in which a defect may give rise to danger.

Those parts must be identified in the scheme. The user or owner must ensure the scheme has been drawn up, or certified as suitable, by a competent person, and that its content is reviewed at appropriate intervals by a competent person and modified if they recommend changes.

Regulation 8 also says no one may draw up or certify a scheme unless it is suitable and:

specifies the nature and frequency of examination;
specifies any measures needed to prepare the pressure system for safe examination (beyond what the user or owner could reasonably take without specialist advice); and
where appropriate, provides for an examination before the system is used for the first time.

"Suitable" means suitable for preventing danger from the parts of the system included in the scheme.

What INDG178 says a typical scheme contains

HSE's leaflet INDG178 lists typical contents of a written scheme of examination, including:

identification of the items of plant or equipment within the system;
those parts of the system which are to be examined;
the nature of the examination required, including inspection and testing of protective devices;
the preparatory work needed for safe examination;
where appropriate, any examination needed before first use;
the maximum interval between examinations;
critical parts which, if modified or repaired, should be examined by a competent person before the system is used again;
the name of the competent person certifying the scheme; and
the date of certification.

INDG178 also says an item should be included if its failure could unintentionally release pressure and the resulting release of stored energy could cause injury. Users and owners decide the scope of the scheme; they may take advice from engineering staff, inspection bodies or consultants, but the legal responsibility for defining scope rests with them.

Examples that help place heating plant

INDG178 gives examples of systems that are likely to need a written scheme. Among those relevant to commercial heating and plant rooms are: a steam boiler and associated pipework and protective devices; a compressed air receiver and associated pipework where pressure (bar) × internal capacity (litres) is 250 bar litres or more; and a fixed LPG storage system supplying fuel for heating in a workplace. Systems HSE lists as not likely to need a scheme include an office hot water urn and a portable compressed air receiver below the 250 bar litre threshold. Those examples are guidance only; you must decide whether your own system is covered.

HSE's PSSR page also notes that there are many exceptions in Schedule 1, and that L122 helps you decide which regulations apply. Do not rely on a blog post to decide an exemption for your site.

Who is the duty holder, and who is the competent person?

HSE's PSSR overview says employers (duty holders) include the user of an installed system (one that is not mobile, such as a steam boiler) and the owner of a mobile system. For hired or leased equipment, the user should make sure a written scheme is in place and that the examination certificate is current. Schedule 2 allows a supplier of an installed system to assume responsibility in writing for the WSE, operation, maintenance and record keeping.

HSE summarises the competent person's role as including: carrying out examinations in accordance with the WSE; reviewing the WSE and confirming it is suitable; producing a written report for each examination; notifying the user or owner of repairs required; identifying action where there is imminent danger; agreeing postponements where appropriate; and drawing up or certifying written schemes. An in-house competent person should be independent from the organisation's operating functions and have authority to stop use of the pressure equipment if needed. INDG178 adds that users are free to select any competent person, but should take all reasonable steps to ensure they can demonstrate the necessary knowledge, experience and independence, and points to UKAS accreditation as one way to judge competence.

HSE's "Using pressure systems" page also reminds users to know the operating conditions and safe operating limits, fit suitable protective devices and keep them working, carry out suitable maintenance, train people who operate or maintain the plant, have equipment examined under PSSR, and choose a competent person with the necessary knowledge, skills and independence.

Examination is not the same as day-to-day maintenance

A written-scheme examination is a periodic, competent-person examination of the parts listed in the scheme. It does not replace regular maintenance of boilers, heaters, controls or pipework. Where gas appliances are involved, gas work must still be carried out by a Gas Safe registered engineer under the Gas Safety (Installation and Use) Regulations 1998. Trained site staff can help by keeping visual and gauge logs, reporting abnormal readings, and making sure examination reports and the written scheme itself are filed where insurers, landlords and auditors can find them. Site staff should not adjust, cap, plug or test-lift relief valves, and they should not open pressure vessels or change protective-device settings.

How this links to commercial gas safety and planned maintenance

On many commercial sites the pressure-system duties sit alongside gas safety duties. A written scheme does not remove the need for annual commercial boiler or heater servicing, gas tightness work where required, or planned preventive maintenance. For inspections and records that support the gas side of your compliance file, see our commercial gas safety inspection page. For scheduling engineer visits so examination dates and manufacturer service intervals do not get missed, see PPM and planned maintenance. Related reading on this blog includes our commercial plant room safety checklist and pressure relief valve checks on industrial water heaters.

Safety note

Under the Gas Safety (Installation and Use) Regulations 1998, gas work must be carried out by a Gas Safe registered engineer, and we apply that rule on every site. Don't attempt DIY work on gas appliances, burners, flues or safety devices. On pressure systems, trained site staff should stick to visual and gauge checks, log the readings and report anything abnormal. Never adjust, cap, plug or test-lift a relief valve yourself.

Talk to a Gas Safe commercial engineer

Fast Commercial Boiler Help is a Gas Safe registered (985448) commercial heating business based at 4 Market Hill, Clare, Sudbury, Suffolk CO10 8NN. Our team of over 10 local engineers covers East Anglia and East London, working on commercial boilers, plant rooms, water heaters, and warm air, radiant and unit heaters. We work on commercial premises only.

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Frequently asked questions

What is a written scheme of examination for heating plant?

HSE's INDG178 describes a written scheme of examination as a document about selected items of plant that form a pressure system, operate under pressure and contain a relevant fluid. Under PSSR regulation 8 it must cover all protective devices, every pressure vessel and every pipeline where a defect may give rise to danger, and pipework where a defect may give rise to danger, and it must be drawn up or certified by a competent person.

When does PSSR apply to commercial heating plant?

PSSR applies to systems containing a relevant fluid. HSE lists steam at any pressure, compressed or liquefied gas (including air) above 0.5 bar, pressurised hot water above 110°C, and gas dissolved under pressure in a solvent (acetylene). Many low-temperature hot water heating systems are outside the written-scheme requirement. Steam plant, high-temperature hot water and qualifying compressed air systems usually need one. A competent person can confirm for your site.

Who is responsible for the written scheme — the site or the engineer?

The user of an installed system (or the owner of a mobile system) has the legal duty under regulation 8 not to operate the system without a suitable written scheme. INDG178 says users or owners define the scope of the scheme; they may take advice, but the legal responsibility rests with them. A competent person draws up or certifies the scheme and carries out examinations to it.

What must a PSSR written scheme of examination include?

Regulation 8 requires the scheme to specify the nature and frequency of examination, any specialist measures needed to prepare the system for safe examination, and where appropriate an examination before first use. INDG178 also lists typical contents such as identification of plant items, parts to be examined, preparatory work, maximum intervals, critical parts after modification or repair, and the name and date of the certifying competent person.

Does a written-scheme examination replace boiler servicing?

No. Examination under the written scheme is a periodic competent-person examination of the parts listed in the scheme. It does not replace manufacturer servicing, planned maintenance, or gas work by a Gas Safe registered engineer under the Gas Safety (Installation and Use) Regulations 1998. HSE also expects users to maintain pressure systems and train the people who operate them.

Sources and further reading

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General guidance only. This article is general information for commercial premises. It is not a substitute for advice from a competent engineer who has seen your site and equipment, or for the manufacturer's instructions. Duty holders remain responsible for their own legal compliance.