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