Portable appliance testing (PAT) is the process of checking that electrical equipment with a plug is safe to use, and it is more than just clipping a tester onto a lead. Done properly, it runs from everyday user checks, through a formal visual inspection, to a combined inspection and electrical test by a competent person. This guide walks through each step, explains what the tester actually measures, and shows how the results should be recorded.
Step 1: everyday user checks
The first line of defence costs nothing and happens every day. Anyone using an appliance should give it a quick look before switching it on, and this is the most frequent form of checking in any workplace. Watch for a damaged plug or casing, cuts or fraying in the cable, scorch marks, or a lead that has been repaired with tape. If something looks wrong, the appliance should be taken out of use until it is checked.
These user checks catch the majority of obvious faults between formal inspections, which is exactly why they matter. They are not recorded formally, but they keep dangerous equipment out of service in the gap between scheduled tests.
Step 2: the formal visual inspection
The second step is a documented visual inspection by a competent person. Studies of appliance faults consistently show that most defects are found by looking, not by testing, so this stage does a lot of the work. The inspector checks the plug wiring and fuse rating, the condition of the flex and its anchorage, the casing and switches, and whether the appliance is suitable for its environment.
A formal visual inspection can be carried out by someone with less training than full electrical testing requires, provided they are competent to recognise faults and know when to stop. Many items that fail PAT fail at this stage, before a tester is ever connected.
Step 3: combined inspection and testing
The third step adds instrument testing to the visual inspection, and this is where a PAT tester comes in. It applies a series of electrical tests appropriate to the appliance class, confirming that earthing, insulation and connections are sound in ways the eye cannot see. This combined inspection and test is what most people picture when they think of PAT.
The tests carried out depend on whether the appliance is Class I (earthed) or Class II (double insulated). The table below summarises the main ones.
|
Test |
What it checks |
Applies to |
|
Earth continuity |
A sound, low-resistance earth path from the plug to the casing |
Class I |
|
Insulation resistance |
That insulation between live parts and earth is intact |
Class I and Class II |
|
Polarity and lead test |
Correct wiring of plugs, leads and extension cables |
Leads and cords |
|
Functional check |
That the appliance runs safely and draws expected current |
All |
Recording and acting on the results
Every formal test should leave a record: what was tested, when, by whom, the result, and the date of the next test. A pass gets a label; a fail is taken out of service, repaired or replaced, and re-tested. Modern testers store results and download them into PAT software, which removes the paperwork and keeps an audit trail. For the tester's own readings to be trustworthy, it needs regular calibration.
FAQs
Who can carry out PAT testing?
A competent person: someone with the knowledge, training and equipment to inspect and test appliances safely and interpret the results. Formal visual inspection needs less training than combined testing, but both require competence, not just access to a tester.
How often should appliances be tested?
There is no single legal interval. Frequency is risk-based and depends on the appliance type and environment; a power tool on a construction site is checked far more often than a computer in an office. User checks and visual inspections happen more frequently than full testing.
What makes an appliance fail?
Common failures include a damaged flex or plug, poor earth continuity on a Class I appliance, low insulation resistance, or incorrect fuse rating. Many of these are caught at the visual inspection stage before testing.
Getting the process right protects people and keeps you compliant. If you need the right instrument or want your team trained to do this properly, speak to us about choosing a PAT tester and our calibration service.