What Is PAT Testing and What Does It Involve?

PAT testing (portable appliance testing) is the examination of electrical appliances and equipment to make sure they are safe to use. It combines a careful visual inspection with electrical tests, because some faults, like a broken earth wire inside a flex, cannot be seen. The IET publishes the industry's Code of Practice for In-service Inspection and Testing of Electrical Equipment, now in its 5th edition, which is why you will sometimes see the work called "in-service inspection and testing".

What PAT testing is for

PAT testing exists to catch appliances that have become dangerous through wear, damage or misuse before they shock someone or start a fire. The legal background is the Electricity at Work Regulations 1989, which say electrical systems must be maintained to prevent danger so far as is reasonably practicable. The regulations do not mention PAT by name. Testing is simply one of the most practical ways for a business to show it is meeting that duty. That is how we treat PAT testing for offices, shops and rented properties in Wolverhampton, Telford and Shropshire: as evidence of maintenance, not a sticker exercise.

It is one layer of three. HSE guidance describes user checks (staff looking at the plug, lead and casing before use), formal visual inspections by a trained person, and a combined inspection and test. The first two catch most faults. The combined test catches the ones you cannot see.

What needs PAT testing?

Anything that plugs into the mains and can be moved is in scope. HSE's guidance lists typical examples, and they fall into a few groups:

• Portable items: kettles, vacuum cleaners, heaters, fans, desk lamps, irons, toasters and hairdryers.

• Movable but rarely moved: fridges, microwaves, photocopiers, vending machines, washing machines and desktop computers.

• Leads and chargers: extension leads, multi-way adaptors, IEC "kettle" leads and mains battery chargers.

• Hand-held items wired in: a hairdryer wired into the wall of a hotel room is still a portable appliance.

Some things are out of scope. Battery powered equipment under 40 volts does not need testing, and neither does the phone or laptop battery itself (the mains charger does). Large wired-in equipment such as a water boiler is part of the fixed installation, so it is covered by the fixed wiring inspection rather than PAT.

Extension leads deserve a special mention. They get stood on, overloaded and wrapped round chair legs, and HSE guidance treats leads that are not dedicated to one appliance as items in their own right. If the tester finds adaptors plugged into adaptors, that is a sign the area needs more sockets, not more leads.

Class I and Class II appliances: why the difference matters

The class of an appliance decides how much testing it needs. HSE groups equipment into two basic types of construction.

A Class I appliance is earthed. It has a metal case or metal parts connected to the earth pin, so if a live wire comes loose and touches the case, the fault current flows to earth and the fuse or circuit protection disconnects it. If that earth path is broken, the case can become live without anyone knowing. That is why HSE recommends Class I equipment has a portable appliance test to confirm the earth connection is sound. Kettles, irons, some floor cleaners and some kitchen equipment are typical examples.

A Class II appliance is double insulated. Extra insulation stops you touching live parts even if there is a fault, so it does not rely on an earth. It carries the symbol of a square inside a square. HSE says Class II equipment does not need a portable appliance test, but it still needs user checks and visual inspections, because the casing itself is the safety feature. A cracked casing on a double insulated drill is a failure.

If you cannot find the double square symbol, HSE advises treating the item as Class I and testing it.

What does PAT testing involve?

A visit follows the same pattern for each item, whoever carries it out.

The visual inspection

The tester unplugs the item and looks at the lead, plug and casing for damage, heat marks, taped joins and signs of water or dust. On a rewireable plug they remove the cover and check that the fuse is the correct rating and a proper cartridge fuse, the wires go to the right terminals, the screws are tight, the cord grip holds the outer sheath and no bare copper is showing. On a moulded plug, only the fuse can be checked.

They also look at how the item is used. Is it suitable for the job and the place? Has anything changed since the last visit? Has a user reported a problem?

The electrical tests

The tests depend on the class of the item. For Class I equipment, the key tests confirm that the earth path is continuous and that the insulation between live parts and the case has not deteriorated. For extension leads and IEC leads, the tester also confirms correct polarity, so live and neutral are not reversed. The instrument either gives a simple pass or fail, or gives readings the tester has to interpret, and HSE notes the second needs more electrical knowledge.

The result

Each item gets a pass or fail. Most testers fix a label to it and record the result against a description and location. There is no legal requirement to label or keep records, but a record is how you show the maintenance is happening and how you spot trends, such as one area where leads keep getting damaged.

What happens if an item fails a PAT test?

It is taken out of use straight away. HSE guidance says damaged or faulty equipment should be removed from use and either repaired by someone competent or disposed of so it cannot be used again.

Many failures are simple. A wrong fuse, a cracked plug or a lead that has pulled out of its cord grip can often be put right on the spot and the item retested. HSE guidance says a combined inspection and test is justified after any repair, so a repaired item should be tested again before it goes back into service. Items with damaged casings, scorched internals or failed insulation are usually not worth repairing.

How often and who can do it

How often depends on the type of equipment and how hard it is used, not a fixed annual rule. The law sets no fixed frequency, HSE says annual testing is not always necessary in low risk environments, and our guide to how long a PAT test lasts sets out the suggested starting intervals.

A PAT test does not have to be done by an electrician, but the person needs the right equipment, training in using it and the knowledge to interpret results. Visual inspections can be done by a sensible member of staff who has had simple training. For landlords the picture is a little different, and PAT testing for landlords covers what applies to rented homes.

If you are not sure what in your building needs testing, send us a rough list of what you have and we will tell you which items need a full test and which only need a look.

PAT testing questions, answered

Do staff's own appliances need PAT testing?

They fall under the same duty. HSE guidance says the duty covers any electrical equipment your employees use at work, whether it is their own or supplied by you, so a personal heater or phone charger brought into the office should be included or banned.

Does PAT testing check the wiring in the walls?

No. PAT covers equipment that plugs in. The sockets, circuits and consumer unit are the fixed installation, which is checked by an Electrical Installation Condition Report as part of wider electrical maintenance.

Is a PAT pass a guarantee the item is safe until the next test?

No. HSE points out that a test only shows the item was safe on the day. User checks between tests are what catch the lead that gets crushed next week.