Building surveys

An indoor air survey at a city facility is usually arranged to establish the underlying reason for an indoor air issue in the building’s indoor air or to acquire initial data for a renovation project.

We handle some 200 condition surveys per year. We also perform radon measurements, among other things. Condition surveys are realised to provide information for the planning of both minor repairs and major renovations. In addition, we monitor the conditions in the facilities and the success of repairs, as well as investigate the causes of indoor air issues and other damage and defects.

In 2014–2023, we commissioned approximately 2,000 surveys on the city’s facilities. Most of them involved service buildings such as schools, day-care centres or social services and health care facilities. 

An order for an survey is placed with an external consultant. We apply commonly accepted survey methods. Strict quality criteria are in place for surveyors and survey methods, and the content of the surveys is defined on a case-by-case basis.

Usually, the survey report is complete some 4–6 months after the survey starts. During the survey phase, time is spent going over construction drawings and any previous surveys, performing field surveys, analysing laboratory samples, and writing and reviewing the report. Observations that require further surveys may be made during the process. The report will be used as a basis for a plan of the necessary repairs.

How is indoor air investigated?

There are usually several reasons for the deterioration of the indoor air quality in a building. An indoor air specialist will familiarise themselves with the building, examine the construction drawings, find out about the building’s repair history and visit the building themselves.

Indoor air investigations are explained in Finnish in this video.

Investigating indoor air

The City of Helsinki has an established operating model to investigate indoor air issues in buildings. Multidisciplinary cooperation is used to solve the problem.

What do the surveys comprise?

There can be several simultaneous factors that affect the quality of indoor air, which is why the surveys must be sufficiently extensive, and the building must be examined as one unit. An indoor air survey can include measuring and reviewing the following:

  • A structural risk analysis: structure types and technical operating methods of the structures from the perspective of moisture
  • Reasons for and extent of moisture damage through measures such as measuring moisture levels, opening structures and taking samples of materials for microbial analysis
  • Indoor air temperature and humidity and the temperature of supply air
  • Cleanliness of the ventilation system, air volumes and the ‘flushing out’ of the premises, i.e. the distribution of clean supply air in the rooms
  • Condition of building services
  • Differential pressure between the outdoor air and the interior, e.g. between the crawlspace and rooms
  • Carbon dioxide content in indoor air
  • Concentrations of chemical compounds in materials and indoor air
  • Occurrence of mineral wool fibres
  • Hazardous substances in materials, such as asbestos and PAHs

Frequently asked questions about indoor air surveys

Assessment of conditions

If necessary, an assessment of the conditions can be performed alongside or after the condition surveys. Its purpose is to assess whether the indoor air conditions in the premises deviate from the norm.

The assessment is primarily based on technical surveys of indoor air and moisture conditions. It considers the extent, severity, location and potential indoor air connection of the sources of impurities, as well as other factors influencing the spread of the impurities, such as the functionality of the ventilation system and differential pressure. Exceeded reference values alone do not allow for any conclusions to be drawn on the conditions and their significance.

Radon measurements

Radon is an odourless, tasteless and colourless radioactive noble gas produced in the Earth’s crust as a decay product of uranium and thorium. The radioactive decay products of radon increase the risk of lung cancer. Indoor radon levels are higher in Finland than in most other countries due to geology, structural engineering methods and the climate. Radon can enter the indoor air through gaps in the floor structure of a building. 

The City of Helsinki investigates the radon concentrations at its workplaces. These measurements are based on the Radiation Act, according to which an employer is obligated to investigate the radon exposure of its employees.

The radon measurements are carried out in close cooperation with the city’s various divisions. The Urban Environment Division’s indoor air team is in charge of coordinating the measurements, which are implemented by the site contact persons. The measuring process has been made as easy as possible with detailed instructions.

Since the enactment of the new Radiation Act in 2018, the City of Helsinki has carried out radon measurements for approximately 850 buildings (situation in spring 2024). Surveyed targets include daycare centres, playground buildings, as well as cultural, leisure, and social services and health care facilities.

Radon concentrations measured at the City of Helsinki's workplaces have generally been low. The reference value for radon has been exceeded in about 5% of the targets. Based on further measurements, radon concentrations have also been low in these locations when ventilation is on, with a few exceptions. We are developing the monitoring measures for these targets.

Read more: Radon in Finland (Radiation and Nuclear Safety Authority)(Link leads to external service)