NEN 3140 inspection: how often and what is checked?

A NEN 3140 inspection is a periodic check of your fixed electrical installation for safety. It consists of a visual inspection, measurements and tests, recorded in a report. NEN 3140 does not state a fixed interval. The installation responsible person (IV) decides how often inspections take place, based on the risks. In practice, for an ordinary business installation, this often comes down to once every three to five years.

The legal basis is article 7.4a of the Arbobesluit (Dutch Working Conditions Decree) . Work equipment, which includes installations, must be tested “as often as is necessary to guarantee its good condition” (zo dikwijls dit ter waarborging van de goede staat noodzakelijk is). If a certified company carries out the inspection, it is called a SCIOS Scope 8 inspection. The fire risk inspection for your insurer is something different: that is Scope 10.

A NEN 3140 inspection covers the fixed installation: distribution boards, cabling and wall sockets. You test electrical tools and extension leads separately. See testing electrical tools.

How often must a NEN 3140 inspection take place?

Since the amendment of 2019, the installation responsible person (IV) records how often a visual check takes place. Only if nothing is recorded does the interval for the visual inspection remain yearly. This is stated on the NEN page on low-voltage installations .

For the full inspection with measurements, the standard gives no number. Inspection companies and insurers commonly cite three to five years. The harsher the conditions, the shorter the interval. An office can wait longer than a wet production hall or a building site.

Factor	Shorter interval if…	Longer interval if…
Environment	Moisture, dust, vibration, heat	Dry, clean office space
Use	The installation is often changed or extended	The installation stays the same for years
Age	Old installation, earlier defects	New installation without findings
Who works with it	Many changing or temporary employees	A fixed, well-instructed team
Consequences of failure	Fire-hazardous substances, public present	Limited consequences

Example: a reasoned inspection schedule

A fictional company with an office, a workshop and a warehouse records it as follows. The intervals are the IV’s own choice, not a requirement from the standard.

Part of the installation	Visual check	Full inspection with measurements	Justification
Office	Yearly	Every 5 years	Dry environment, few changes
Workshop	Every six months	Every 3 years	Dust, vibration, many changes
Warehouse with forklift charging stations	Yearly	Every 3 years	High load, fire risk when charging
Site power distribution boards	At each set-up	At each new location	Arbobesluit art. 7.4a para. 2

The most important thing is the justification. If you can explain why you chose five years, you stand strong with the Netherlands Labour Authority (Nederlandse Arbeidsinspectie). An interval without an explanation is weaker.

What is checked during a NEN 3140 inspection?

The inspection consists of three parts. The inspector decides, based on the installation, which measurements are needed.

Component	What the inspector does	Example of a finding
Visual inspection	Looks at distribution boards, cables, covers, labels and schedules	Cover plate missing from the workshop distribution board
Measurements	Measures, among other things, insulation resistance and the continuity of the protective conductor	Insulation resistance of group 7 too low
Tests	Tests RCDs for tripping time and with the test button	RCD does not trip within the limit value
Documentation	Checks whether the schedules match reality	New group in the machine hall not on the drawing

What you test yourself on an RCD is set out on Testing an RCD. Since 2019 the inspection also checks whether you can carry out safe maintenance and clearly isolate parts of the installation. A distribution board without a recognisable main switch therefore also results in a finding.

Who may carry out a NEN 3140 inspection?

The Arbobesluit only states that testing is carried out by “a competent natural person, legal entity or institution” (een deskundige natuurlijke persoon, rechtspersoon of instelling). In NEN 3140 terms, that is a competent person (VP) with an appointment for inspections. See appointing VPs and VOPs.

You can therefore have your own VP carry out the inspection. Many companies choose an external inspection company with a SCIOS certificate for Scope 8. That gives an independent report and a fixed inspection plan, which carries more weight with insurers and clients.

Example of a NEN 3140 inspection report

A good report is more than a list of measured values. It says what is wrong, how serious it is and when it must be fixed. A summary looks like this:

Field	Content
Object	Business premises at Industrieweg 12, main distribution board and 4 sub-distribution boards
Date and inspector	14 October 2026, J. Bakker (VP, SCIOS Scope 8)
Client and IV	Bakkerij Van Dijk B.V., IV: M. de Wit
Result	Approved subject to conditions, 3 defects
Advice for next inspection	October 2029

No.	Defect	Urgency	Repair deadline	Repaired
1	RCD for group 3 trips too slowly	High	Immediately	15 Oct ✔
2	Schedule for the oven sub-distribution board not up to date	Medium	1 month
3	Cable entry without strain relief at the mixer	Low	3 months

The IV signs off the repair and keeps the report and the proof of repair together. Only then is the inspection truly complete.

What does the inspector or auditor want to see?

The Netherlands Labour Authority, a VCA auditor or an ISO 45001 auditor asks for the same documents:

The latest inspection report, present at the workplace (art. 7.4a para. 6)
Proof that the defects have been repaired
Up-to-date schedules of the installation (art. 3.4 para. 3)
The recorded inspection interval, with its justification
The appointment of the installation responsible person

Common mistakes in the NEN 3140 inspection

Only inspecting, not repairing. A report with open defects is evidence against you.
Seeing the commissioning inspection as an inspection. The test after installation under NEN 1010 is a first verification, not a periodic inspection.
Mixing up Scope 10 and NEN 3140. A fire risk inspection for the insurer does not fully cover your Arbo duty.
Not recording an interval. Then a yearly interval automatically applies to the visual check.
Not updating schedules after a renovation. That is the most common finding.

For what an inspection costs, read NEN 3140 inspection and SCIOS inspection costs.

Frequently asked questions about the NEN 3140 inspection

Must the installation be switched off during the inspection?

Not all the time. The visual inspection is usually carried out with the installation in operation. For some measurements, a group must be briefly switched off. Agree with the inspection company when that can happen, for example outside production hours.

Who arranges the NEN 3140 inspection in a rented property?

The Arbo duty lies with the employer who has people working there, so usually the tenant. The installation often belongs to the landlord. Therefore, record in the lease who is the installation responsible person, who arranges the inspection and who pays for repairs.

Does the inspection interval change with the new NEN 3140?

A revised NEN 3140 was out for public comment as a draft in 2026. Until the final version appears, you work to NEN 3140:2011+A3:2019, with an interval that the IV records based on risk.