PAT Testing — Practitioner Reference

This reference provides practitioner-level depth on UK PAT testing — the EAWR 1989 framework, the IET Code of Practice methodology, the three-tier inspection regime, Class I/II/III protocols, risk-based frequency determination, and the records regime. The layman version is at /pat-testing.

1. Legal framework

The duties:

• The Electricity at Work Regulations 1989 (EAWR) — SI 1989/635. The operative regulations.
• The Health and Safety at Work etc. Act 1974 (HSWA) — parent duty.
• The Provision and Use of Work Equipment Regulations 1998 (PUWER) — equipment as work equipment.
• The Management of Health and Safety at Work Regulations 1999 (MHSWR) — risk assessment.
• The Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020 — for residential rentals (separate to the PAT regime).
• The Personal Protective Equipment at Work Regulations 1992 (as amended 2022) — for equipment as PPE.

EAWR 1989 Regulation 4(2) is the operative provision:

"As may be necessary to prevent danger, all systems shall be maintained so as to prevent, so far as is reasonably practicable, such danger."

The "systems" includes portable equipment. The "maintained" duty is functional; PAT testing is the recognised industry method of demonstrating that the functional duty is met.

In Northern Ireland, the equivalent regulations are the Electricity at Work Regulations (Northern Ireland) 1991.

2. The IET Code of Practice

The IET Code of Practice for In-Service Inspection and Testing of Electrical Equipment is the operative industry standard. Current edition: 5th Edition, published 2020.

2.1 The Code's status

The Code is not a regulation. Compliance is not statutory. However:

• The Code represents the practitioner consensus on competent practice
• HSE and the enforcing authorities treat the Code as evidence of competent practice
• Insurers typically require regimes operating to the Code
• The Code is the reference against which competent person work is judged

Departure from the Code without good reason is hard to defend.

2.2 Code structure

The 5th Edition covers:

• The legal and standards framework
• Equipment classification (Class I, II, III)
• The three-tier inspection regime
• Risk-based frequency determination
• Testing protocols by equipment type
• Records and labelling
• Competence requirements
• Specific guidance for common environments (offices, education, healthcare, construction, hire)

3. The three-tier inspection regime

The IET Code identifies three distinct inspection types that, together, constitute the in-service regime. Most lay understanding focuses only on the third.

3.1 User checks

The simplest and most frequent check. The user looks at the equipment before each use:

• Cable damage (cuts, abrasion, fraying)
• Plug damage (cracked casing, burnt pins, missing fuse cover)
• Casing damage (cracks, missing parts)
• Signs of overheating (discolouration, melting, smell)
• Appropriate use for the equipment

User checks:

• Take seconds
• Require no qualifications
• Do not require test equipment
• Are not formally recorded (records of training and induction are the documentary evidence)

The value: catching damage between formal inspections — a cable that became frayed yesterday, a plug that cracked last week, signs of overheating that appeared in recent use. User checks are the most cost-effective single element of any PAT regime.

3.2 Formal visual inspection

A more structured visual inspection by a competent person:

• Cable condition along its full length
• Plug condition — cover, cord grip, fuse rating, pin condition
• Casing condition
• Indicator lamps, switches, controls
• Signs of overheating, damage, contamination, unauthorised modification
• Fitness for environment

Formal visual inspection:

• Does not require test equipment
• Requires basic electrical competence (recognising fault conditions, understanding equipment use)
• Identifies a high proportion of faults that the combined inspection and test would also identify
• Should be recorded against the equipment inventory

The Code emphasises formal visual inspection as a significant element of the regime. Many faults are identified at this stage without the time and cost of full electrical testing.

3.3 Combined inspection and test

The full inspection most commonly understood as PAT. Combines the formal visual inspection with electrical testing using a portable appliance tester.

Tests typically include:

• Earth continuity (Class I equipment) — verifies the earth connection from the appliance metal to the supply plug earth pin
• Insulation resistance — verifies that insulation is intact
• Polarity check — verifies correct connection (extension leads particularly)
• Functional test — verifies the equipment operates
• Earth leakage — verifies leakage current within acceptable limits
• Touch current (Class II only) — verifies the equipment surface is at safe potential
• Lead polarity (extension leads) — verifies wiring continuity

The combined inspection and test is the most thorough check and produces the recognised PAT certificate. It is also the most time-consuming and the only inspection type requiring specific test equipment and specific qualifications.

3.4 Why the three-tier structure matters

A regime that focuses only on combined inspection and test:

• Catches faults at the formal test interval only
• Misses damage occurring between tests
• Cannot scale to large equipment populations efficiently
• Treats compliance as a periodic event rather than a continuous regime

A regime operating all three tiers:

• Catches most damage at user check (before use)
• Catches the rest at formal visual inspection
• Reserves combined inspection and test for the systematic electrical verification it is best at
• Operates continuously rather than periodically

The three-tier regime is the IET Code's structural insight, and the area where many commercial regimes fall short.

4. Equipment classification

UK portable equipment is classified by protection against electric shock:

4.1 Class I

Protection by basic insulation plus a protective earth connection. Identifiable by:

• Three-core supply cable (line, neutral, earth)
• Earth pin on the supply plug
• Often metal casing
• No specific identification symbol

Testing protocol:

• Earth continuity — must be within specified limit (typically 0.1Ω + cable resistance per IET Code)
• Insulation resistance — typically 1MΩ minimum at 500V DC

4.2 Class II

Protection by double or reinforced insulation, no earth required. Identifiable by:

• Two-core supply cable (line, neutral only)
• The double-square symbol on the rating plate
• Often plastic or fully insulated metal casing

Testing protocol:

• Earth continuity — not applicable (no earth)
• Insulation resistance — typically 2MΩ minimum at 500V DC (some sources specify 7MΩ for double-insulated)
• Touch current — may be tested to verify no leakage through insulation

Applying earth continuity tests to Class II equipment produces meaningless readings; applying inappropriate test voltages can damage sensitive electronics.

4.3 Class III

Protection by supply at safety extra-low voltage (SELV), typically below 50V AC or 75V DC. Identifiable by:

• Power supplied from a SELV source (transformer, battery, charger)
• Three-diamond symbol (where labelled)
• Common in low-voltage equipment, chargers, battery-powered tools

Testing protocol:

• The SELV equipment itself does not require electrical testing in the same form as Class I/II
• The supply unit (transformer or charger) requires testing as Class I or Class II as appropriate
• The Class III equipment is inspected visually

4.4 IT and electronic equipment specifics

Modern IT and electronic equipment frequently includes:

• Switch-mode power supplies with high earth leakage currents
• Sensitive electronics that may be damaged by inappropriate test voltages
• Functional earthing (earth used for noise reduction) distinct from protective earthing

Testing protocol adjustments:

• Insulation resistance at 250V DC may be appropriate (rather than 500V DC) for sensitive equipment
• Earth leakage limits adjusted for known high-leakage equipment (typically up to 3.5mA)
• Manufacturer guidance for the specific equipment should be consulted

The IET Code provides specific guidance for IT and electronic equipment.

5. Risk-based frequency determination

The IET Code 5th Edition provides risk-based frequency tables. The frequencies are not regulations but represent practitioner consensus.

5.1 Frequency factors

Frequency should reflect:

• Equipment classification (Class I generally warrants more frequent inspection than Class II)
• Use intensity (continuous vs occasional)
• Environment (controlled office vs harsh industrial)
• User profile (trained employees vs public)
• Mobility (fixed location vs frequently moved)
• Previous failure history

5.2 IET Code frequency framework — typical intervals

Office and shop equipment (low-stress environment):

| Equipment type | User checks | Formal visual | Combined I&T | | --- | --- | --- | --- | | IT equipment, fixed | None | 24-48 months | None / 5 years | | IT equipment, portable | None | 12-24 months | 24-48 months | | Hand-held appliances (Class I) | Pre-use | 6-12 months | 12-24 months | | Hand-held appliances (Class II) | Pre-use | 12-24 months | 24-48 months | | Movable equipment | None | 12 months | 24 months | | Extension leads | Pre-use | 6 months | 12 months |

Public-use equipment (hotels, gyms, public buildings):

| Equipment type | User checks | Formal visual | Combined I&T | | --- | --- | --- | --- | | Hand-held appliances | Weekly/monthly | 6-12 months | 12 months | | Movable equipment | Weekly/monthly | 6-12 months | 12 months | | Cables and extension leads | Weekly | 3-6 months | 12 months |

Schools, restaurants, kitchens:

| Equipment type | User checks | Formal visual | Combined I&T | | --- | --- | --- | --- | | Kitchen appliances | Pre-use | 6 months | 12 months | | Cleaning equipment | Pre-use | 6 months | 12 months | | Hand-held tools | Pre-use | 6 months | 12 months |

Industrial environments and high-stress use:

| Equipment type | User checks | Formal visual | Combined I&T | | --- | --- | --- | --- | | Hand-held tools | Pre-use | 1-3 months | 6-12 months | | Movable plant | Pre-use | 1-3 months | 6-12 months | | Cables and extension leads | Pre-use | 1 month | 3 months |

Construction sites:

| Equipment type | User checks | Formal visual | Combined I&T | | --- | --- | --- | --- | | 110V tools | Pre-use | 1 month | 3 months | | 230V tools | Pre-use | Weekly | 1 month | | Cables | Pre-use | Weekly | 1 month | | Movable plant | Pre-use | 1 month | 3 months |

Hire equipment:

• Pre-use user check
• Formal visual inspection before each hire
• Combined I&T per manufacturer/hire company specification (typically 12 months)

5.3 Adjusting frequencies

The frequencies are starting points. Adjustments:

Reduce frequency where:

• Equipment is in low-stress environment with reliable user awareness
• Equipment is robust Class II with proven track record
• Recent inspections show consistently positive results
• The risk assessment supports reduction

Increase frequency where:

• Equipment is in harsh environment or high-stress use
• Equipment is used by public or untrained users
• Recent inspections show emerging fault patterns
• Equipment is approaching end of service life
• Recent incidents or near-misses warrant additional verification

The frequency determination should be documented as part of the risk assessment, not adopted by default.

6. New equipment

A common myth: new equipment must be PAT tested before first use.

The IET Code position:

• New equipment, supplied by reputable manufacturer, in original packaging, with CE / UKCA marking, is presumed safe for first use
• A user-level visual check before first use is recommended
• Formal visual inspection or combined inspection and test is not required at first use
• Subsequent inspection follows the normal cycle

The "PAT test before first use" service offered by some contractors provides testing that the Code does not require. Operators are not non-compliant for skipping it. Where it is offered, the value is essentially confirming damage in transit — which is a goods receipt function rather than a compliance function.

7. Scope — what is in and what is out

7.1 In scope

• Anything plugged into the fixed installation via a 13A plug or industrial connector
• Extension leads (often the most common fault point)
• Multi-way adaptors and IEC distribution leads
• IT chargers, laptop power supplies, monitor cables (often overlooked)
• Portable hand tools
• Hire equipment
• Kitchen appliances
• Personal equipment brought from home for work use (where permitted)

7.2 Out of scope

• Hardwired equipment (no plug) — covered by the EICR regime
• Fixed installation itself — wiring, distribution boards, sockets
• IT equipment connected by structured data cabling (covered separately)
• Specialist medical, scientific, or industrial equipment with its own inspection regime
• Equipment owned by employees and not used for work
• Visitor equipment (e.g., guest laptops in hotels)

7.3 Boundary cases

Plug-in light fittings. Lampholders permanently connected by plug are in scope. Lampholders hardwired are out (EICR).

Multi-occupied buildings. The duty extends to the equipment of the occupier of each space. Common-area equipment is the landlord's responsibility; tenant-area equipment is the tenant's.

Customer-brought equipment in public spaces. Cafes, public access spaces where customers plug in personal devices. The duty is on the proprietor to provide a safe supply (EICR scope) and to control equipment that becomes a workplace issue, but not generally to inspect customer-brought devices.

Equipment moved between premises. Where employees use equipment at home and in office, the equipment is in scope of the employer's regime. Hybrid work expands this category significantly.

8. Testing protocols by test type

8.1 Earth continuity (Class I only)

Verifies the earth connection from accessible metal of the appliance to the earth pin of the supply plug.

Test current: typically 1.5A nominal under IET Code. Higher current options (10A, 25A) available on some testers; higher current produces more reliable result for higher-resistance connections but takes longer and may damage some equipment.

Pass criterion: typically 0.1Ω + cable resistance (where the cable resistance is calculated from cable specification). Specific limits per IET Code 5th Edition tables.

Common failures:

• Poor earth termination at the plug
• Broken earth conductor within the cable
• Loose earth screw at the appliance
• Faulty earth bonding within the appliance

8.2 Insulation resistance

Verifies insulation between live conductors (line and neutral combined) and the earth.

Test voltage: typically 500V DC for general equipment; 250V DC for sensitive electronics.

Pass criterion: typically 1MΩ minimum (Class I) or 2-7MΩ minimum (Class II); manufacturer specification may set different limits for specific equipment.

Common failures:

• Moisture ingress producing reduced insulation
• Insulation deterioration through age, heat, or mechanical damage
• Internal damage producing partial short

8.3 Polarity

Verifies that live and neutral are correctly connected on extension leads and similar.

Pass criterion: correct polarity (live to live, neutral to neutral) throughout the lead and at each socket.

Common failures:

• Reversed polarity at one socket of a multi-way lead
• Lead manufactured incorrectly
• Lead repaired or modified producing crossed connection

8.4 Functional test

Verifies the equipment operates. Limited scope — confirms operation, not safety performance.

8.5 Earth leakage

Verifies leakage current within acceptable limits.

Test method: measure current flowing through the earth conductor during operation.

Pass criterion: typically 0.75mA for portable equipment; up to 3.5mA for IT equipment with high-leakage power supplies.

8.6 Test sequence

The IET Code specifies the test sequence to avoid damaging equipment:

1. Visual inspection first
2. Earth continuity
3. Insulation resistance
4. Functional test
5. Earth leakage (where required)

Testing in wrong sequence can damage equipment — for example, applying insulation resistance test voltage before confirming earth continuity may stress components inappropriately.

9. Labels and certificates

9.1 Labels

PAT testing labels (the small stickers showing the next test date) are widespread but not strictly required by the Code. Their value:

• Operational confirmation that the equipment is in the regime
• Immediate evidence for inspectors and insurers
• Identification of equipment in regimes with mixed history

Label content typically includes:

• Pass / fail indication
• Date of test
• Next test due date
• Tester ID or company

9.2 Certificates

The PAT certificate is the documentary output of the combined inspection and test. Format varies but should include:

• Equipment identification (asset number, description, location)
• Test date and tester ID
• Tests performed and results
• Pass/fail determination
• Recommended retest interval

9.3 The wider records

Beyond the certificate, the records that support defensibility:

• Equipment inventory
• Risk assessment supporting frequency determination
• Inspection schedule
• Results of formal visual inspections
• Combined I&T certificates
• Failures and actions taken
• Removal-from-service evidence
• User check awareness in training records

A logbook of certificates without supporting inventory and schedule is incomplete.

10. Competence framework

The IET Code requires competence proportionate to the work:

10.1 User checks

• Awareness embedded in induction
• Basic understanding of what constitutes damage or fault
• No formal qualification

10.2 Formal visual inspection

• Basic electrical safety awareness
• Documented training to perform the inspection
• Ability to recognise faults at the level expected by the Code

10.3 Combined inspection and test

The recognised competence routes:

• City & Guilds 2377 — In-Service Inspection and Testing of Electrical Equipment (the principal qualification)
• EAL Level 3 — Electrical Equipment Testing
• PASMA / IPAF — Not specifically PAT but show wider competence in some sectors
• ECS PAT card — Electrotechnical Certification Scheme PAT competence card
• Documented in-house training to the IET CoP standard

The qualifications include:

• Test equipment use
• Test protocol understanding
• Result interpretation
• Equipment classification
• Recording requirements

For employed testers, the IET CoP accepts documented in-house training as competence evidence. For external contractors, formal qualifications and current certification are typical.

11. Test equipment

PAT testers vary from basic pass/fail units to advanced data-logging models with manufacturer database integration.

Test equipment considerations:

• Calibration — testers should be calibrated annually (typical industry practice; manufacturer specification may vary)
• Calibration certificate retained as part of the regime records
• Test current selection — appropriate for the equipment type
• Data logging — produces electronic records integrated with asset management systems

Basic pass/fail testers are adequate for small simple inventories. Data-logging testers earn their cost on larger or distributed inventories where electronic records produce significant time savings.

12. Records — the documentary regime

Records that support defensibility:

• Equipment inventory — current, accessible
• Risk assessment supporting frequency determination
• Inspection schedule
• Formal visual inspection results
• Combined inspection and test certificates
• Failure and remedial action records
• Removal-from-service records
• User check awareness (induction records, refresher training)
• Tester competence records
• Test equipment calibration records

Retention should be for the working life of the equipment plus a reasonable period — five years minimum, longer where any incident may be subject to claim or investigation.

13. Specific environment considerations

13.1 Construction sites

Construction is the highest-stress PAT environment. The Code provides specific guidance:

• 110V centre-tapped earth (CTE) supply is preferred for site tools
• Tools at risk of damage during the working day require pre-use user checks
• 110V tools: combined I&T at three-month intervals minimum
• 230V tools (where used): more frequent inspection
• Specific colour-coding (often by month) supports visual identification of current testing status

13.2 Healthcare

Medical electrical equipment is subject to specific standards (BS EN 62353 for in-service testing of medical electrical equipment) in addition to the PAT framework. Specialist competence is required.

13.3 Hire equipment

Hire companies typically operate their own internal PAT regime. The hirer should:

• Receive documentation of recent inspection at hire collection
• Verify the equipment is within current test interval
• Apply local controls (typically formal visual inspection on receipt)

13.4 IT equipment

The IET Code 5th Edition specifically addresses IT equipment:

• Higher earth leakage currents are normal for switch-mode supplies (up to 3.5mA per device)
• Insulation testing at 250V DC may be preferred to 500V DC
• Functional earth distinct from protective earth requires understanding
• Equipment connected by structured cabling (no plug) is out of PAT scope

14. Common compliance deficiencies

Patterns in audited regimes:

• Generic "annual PAT testing" without risk assessment of equipment and environment
• High-stress equipment (construction, kitchens, hire) on same annual cycle as office equipment
• New equipment tested unnecessarily while user checks absent
• Combined inspection and test performed but formal visual element skipped
• Class II equipment subjected to earth continuity testing (producing meaningless readings)
• Failures recorded but no evidence of removal from service
• Inventory absent — records show what was tested but not what should have been
• Multiple contractors over the years with no consolidated picture
• Personal equipment brought from home not in any regime
• Charger and IT cable population entirely overlooked
• Hybrid work equipment (home use) not addressed

The remediation pattern: rebuild the inventory, set risk-based frequencies, document the regime, ensure failures are demonstrably removed from service.

15. Enforcement

PAT-related enforcement typically appears as a component of wider electrical safety enforcement under EAWR and HSWA. Standalone PAT prosecutions are rare; PAT failures more commonly contribute to broader electrical safety findings.

Specific themes:

• Construction sites with inadequate or absent regime
• Hospitality and kitchen settings where equipment failure has contributed to fire
• Hire equipment failures where the duty holder relied on the hire company without verification
• Hospital and care settings where medical equipment testing was inadequate

Sentencing follows the Sentencing Council Guideline for Health and Safety Offences. Standalone PAT prosecutions tend to be lower-tier; PAT failures contributing to fatality or serious injury follow the full sentencing framework.

This pillar should be read alongside the layman version at /pat-testing and the related professional pillars on electrical testing and workplace safety training.