IET Code of Practice — In-service inspection & testing (PAT)

Three levels of check

The Code is built around three layers, not just 'the PAT test':

• User checks — informal, by the person about to use the equipment. Visual look-over for damage to plug, lead and casing.
• Formal visual inspection — by a trained person, on a defined interval, recorded. Catches the majority of faults.
• Combined inspection and test — visual plus electrical tests with a calibrated PAT tester. Less frequent, but produces the documentary record.

Class I vs Class II

Class I equipment relies on earthing for safety — tested for earth continuity and insulation resistance. Class II is double-insulated — tested for insulation resistance and touch current. Test regimes differ and the tester must select the right one. Class III (SELV) typically doesn't require electrical testing.

Risk-based intervals — examples

The Code provides suggested intervals as a starting point; the duty-holder sets the actual interval. Indicative figures (formal visual / combined test):

• Office IT and similar in low-risk areas — 24 / 48 months, or by exception.
• Office portable equipment (kettles, fans) — 12 / 24 months.
• Hotel / commercial kitchen equipment — 6 / 12 months.
• Construction site equipment (110V) — 1 / 3 months.
• Equipment for hire — before each hire.

The tester itself

PAT testers must be calibrated to the manufacturer's recommendation (typically annually) by an accredited calibration provider. The calibration certificate should be kept with the test reports — without it, the test results are not defensible.

Records and labels

The label on the appliance and the report in the file must agree. A label without a matching record (or a record without an identifiable asset) breaks the audit trail. A unique asset ID per item solves it.