Indoor air 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.

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If an indoor air issue is suspected in a building, and the situation cannot be solved by measures such as adjusting the ventilation system and cleaning the facilities, we will examine the building in more detail.

An order for an survey is placed with an external consultant selected on the basis of price and quality criteria for two years at a time. 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.

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

Microbes in an indoor environment refer to bacteria, moulds and yeasts, for example. In layperson’s terms, all these are often referred to as ‘mould’. Microbes and their metabolites are always present, both indoors and outdoors. Microbe concentrations and species vary depending on the conditions such as the season. The microbe concentration of indoor air is affected by factors such as the microbe concentration of outdoor air, dust, human actions and humans themselves, as well as microbial damage. It has been discovered that the microbes in our living environment also have beneficial health effects, which means that not all microbe exposure is harmful.

According to studies, unrepaired moisture damage in a building is one risk factor for respiratory symptoms and asthma. However, it has been impossible to determine any causality between moisture damage and health effects, as it is unknown which factors and mechanisms cause these health effects. Establishing any limit values for specific microbes or results from microbial samples based on the health effects has therefore been impossible. No risk of the development of other diseases has been identified.

Actinomyces are bacteria that grow hyphae and endospores, similar to fungi. Actinomyces are also called actinobacteria. The species include streptomycetes, for example. Actinomyces are very common in the environment and play important roles in nature. Actinomyces are very common in soil, and are often characterised by an earthy, basement smell. Actinomyces can be carried indoors on people’s shoes or outdoor clothing, for example.

When growing inside structures, actinomyces are one of the ‘indicator microbes’ of moisture damage, as they enjoy moist surroundings. Moisture damage provides good growth conditions for many different species of microbes. Small quantities of actinomyces may also enter structures as a result of air leaks, for example.

The detrimental effects of actinomyces on the users of facilities is assessed in the same way as for the other microbes discovered during surveys. Unrepaired moisture and microbial damage, especially if it is extensive, is one of the risk factors for asthma. Moisture and microbial damage can also make other respiratory symptoms worse.

The abbreviation VOC comes from the words Volatile Organic Compounds, while TVOC refers to the measured Total Volatile Organic Compounds.

Indoor air always contains small amounts of up to hundreds of different volatile organic compounds, which come from sources such as construction materials and furniture, cleaning substances, consumer goods and people themselves. New materials release more volatile organic compounds than old ones, but their volume usually decreases to the standard level within 6–12 months. Improved ventilation speeds up this process.

VOC concentrations may also be elevated if materials have got wet, have excessive specific emissions or are old. It is also quite common that the concentration of VOCs is temporarily elevated after the premises have been cleaned. 

Limits have been set for total volatile organic compounds in indoor air, as well as for four individual compounds, in the Decree of the Ministry of Social Affairs and Health on Health-related Conditions of Housing and Other Residential Buildings and Qualification Requirements for Third-party Experts (the ‘Housing Health Decree’). In addition, the Finnish Institute of Occupational Health has determined reference values for specific individual compounds, which indicate whether the concentrations of these compounds are at a normal level. VOCs in indoor air can be one cause of temporary irritation and respiratory symptoms, and they may also cause odour problems.

No, they do not. VOC measurements only detect volatile organic compounds with a boiling point of 50–250°C. These compounds occur as gases in indoor air. 

In addition to VOCs, semi-volatile organic compounds (such as PAHs), highly volatile organic compounds (such as acetone, formaldehyde and alcohols) or particle-bound compounds can occur in indoor air in certain situations. Separate methods are needed to measure the concentrations of these substances. 

Apart from organic compounds, air can also contain inorganic compounds such as carbon monoxide, carbon dioxide, ozone, nitrogen oxides, sulphur compounds or ammonia.

PAHs, or Polycyclic Aromatic Hydrocarbons, are by-products of incomplete thermal decomposition. They can occur in indoor air from sources such as cigarette smoke coming from outdoors and creosote, which is often identified by its distinctive railway sleeper smell. Creosote was used in older buildings as water and moisture insulation (tar paper, bitumen felt). It has also been used as a wood preservative in outdoor structures.

Most PAHs are generated as emissions from traffic, industry and energy production (such as small-scale wood burning), as well as in nature during forest fires, for example. They can also be present in food such as grilled or smoked dishes. 

The quantity and duration of exposure affect the health effects, as does the method of exposure (e.g. by digestion, breathing or touching the compound). PAHs are a large group of compounds with varying health effects. The health effects of the lightest compound, naphthalene, and the heaviest compound, benzo[a]pyrene, have been studied the most extensively. Action limits have been specified for them in the Housing Health Decree.

Benzo[a]pyrene concentrations in outdoor air are monitored in the Helsinki metropolitan area.(Link leads to external service)

Primarily, extensive technical indoor air surveys and moisture surveys are carried out in the building, during which microbial samples of the construction materials are taken. The advantage of these construction material samples is that they help locate the microbial damage, as well as review its extent.

The surveys are started by reviewing the construction drawings to locate areas susceptible to moisture and by arranging an initial site review. Microbial samples are not always necessary if the microbial growth can be seen with the naked eye. For example, moisture and microbial damage detected in connection with water damage can be repaired without any surveys in some cases. Moisture and microbial damage must always be repaired, regardless of the sampling results.

Air leaks refer to improperly sealed areas in structures. The areas can be minuscule spot leaks that can only be detected with tracer tests, or larger gaps or cracks in the material that can also be seen with the naked eye. Air leaks usually occur at wire or pipe lead-throughs and structural joints such as joints between windows and walls.

The principle is that structures should be properly sealed. For example, if there are air leaks through the floor structure of the lowermost storey of a building, impurities from the crawlspace or soil can enter the indoor air if there is negative pressure in the indoor premises.

The effect of an air leak on the indoor air depends on factors such as the condition of the structures and whether the air leak is through a structure or straight from the outside.

Impurities travelling with air leaks may include:

  • Fine particles and other impurities in outdoor air
  • Abnormal microbes from structures
  • Other impurities such as dirt that have accumulated in the structures
  • Microbes from the soil and radon from the ground
  • Microbes from any organic matter left in the crawlspace
  • Cigarette smoke from neighbouring premises or from outdoors

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.

In radon measurements at the workplaces of the City of Helsinki, the radon concentrations have generally been low. In the 2018–2019 and 2019–2020 measurement periods, the limit value for radon was exceeded at approximately 6% of the sites. Additional measurements at the sites with excess concentrations have revealed that the radon concentrations mostly remained low when the ventilation system was on.

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