OVK intervals: how often ventilation must be inspected

The OVK interval is three years for preschools, schools and care premises regardless of ventilation system, three years for apartment buildings and offices with FT or FTX ventilation, and six years for the same buildings with S, F or FX ventilation. One- and two-dwelling buildings have no recurring inspection at all — only a first inspection before the system is taken into use. The intervals are set out in Boverket's regulations on the functional inspection of ventilation systems (BFS 2011:16).

The table

Building	Ventilation system	Interval
Preschools, schools, care premises and similar	All	3 years
Apartment buildings, office buildings, and staff areas and offices in industrial buildings	FT, FTX	3 years
Apartment buildings, office buildings, and staff areas and offices in industrial buildings	S, F, FX	6 years
One- and two-dwelling buildings	FX, FT, FTX	First inspection only, none recurring

The letters describe the system type: S natural ventilation, F extract air, FX extract air with heat recovery, FT supply and extract air, FTX supply and extract air with heat recovery.

The office case — where it most often goes wrong

An office is not its own category with its own interval. Office buildings sit in the same row as apartment buildings, which means the system type alone decides whether it is three or six years. An office with FTX is inspected every three years; an office with extract air only, every six.

It is the most common misreading we see, and it is expensive in both directions: either an inspection is ordered three years early, or it falls due three years late without anyone noticing.

Two more cases that tend to surprise:

• Industrial buildings. The production space itself is not covered by the recurring inspection requirement, but staff areas and offices in the building are and follow the apartment building row. One building can therefore have two answers at once.
• One- and two-dwelling buildings with FT or FTX must be inspected before the system is taken into use, but never afterwards. No recurring OVK does not mean "no requirement" — the first inspection is mandatory.

When does the interval start running?

From the inspection date in the most recent approved report, not from when the report reached the management office and not from the end of the calendar year. A report dated 14 March 2024 on an apartment building with FTX gives a next inspection of 14 March 2027.

The report almost always contains a pre-printed "next inspection" date. Check it against the table above before trusting it — a field filled in by hand may have been calculated on the wrong category, and it is your responsibility as owner, not the inspector's, that the inspection happens on time. How to read the rest of the document: the OVK report field by field.

Is it 3 or 6 years for an office — I get different answers everywhere?

Both answers are online because both are correct, for different systems. Offices with supply and extract ventilation (FT or FTX) have three years; offices with natural ventilation, extract air or extract air with heat recovery (S, F, FX) have six. The deciding source is therefore not the building's use alone, but the row in BFS 2011:16 where building type and system type are read together. If you do not know which system type the building has, it is in the previous OVK report.

When the interval cannot be calculated

Sometimes the preconditions are missing: the building category is unclear, the ventilation system is not stated in the report, or the building is of a type with no recurring OVK interval. Then there is only one honest answer — no date.

Emphyx is built with that rule baked in: the interval engine returns no date for one- and two-dwelling buildings, industrial buildings and buildings whose category cannot be established, and instead raises a task that the category needs to be determined. A guessed statutory date is worse than an empty field, because a guessed date looks finished.

If you have hundreds of buildings to keep track of: how OVK tracking works, and OVK in a municipal housing company describes the working method in a large portfolio.