Sensors revealed sky-high levels of particulate matter indoors

– Very few buildings are completely airtight. With properly balanced ventilation, there should be a slight positive pressure inside, which should keep most particulate matter out. However, we often see that even with just a marginal imbalance, particulate matter is drawn in. When outdoor air quality is poor, the indoor climate is also affected, says indoor climate and ventilation expert at Energy Control, Christian Hope.

‍Above the critical action threshold
Energy Control has done a digital review of some of the sensors the company has in office and commercial buildings in Bergen. To measure the amount of particulate matter indoors, so-called Airthings Space Pro sensors are required. This is one of the most comprehensive indoor climate sensors on the market.
– This is a sensor that measures important indoor climate qualities including CO2, temperature and particulate matter, says Hope.
He does not want to be specific about which buildings Energy Control has recorded high particulate matter concentrations in, but says it applies to both offices and other types of commercial buildings.
– The buildings are located in the Bergen valley, from Minde in the south to the centre of Bergen. We have found varying PM levels, but in one place the level at certain times of day was as high as 41 µg/m³. These are high levels and above what is considered critical, says Hope, adding that they have also seen high levels in other parts of the country.
– Particulate matter is not a Bergen phenomenon. Dry and cold air produces a lot of particulate matter regardless of where you are in the country, says Hope.

‍May experience irritation
‍Normal levels for particulate matter range from 0 to 9 µg/m³. Levels from 10 to 25 are defined as an action threshold where you should monitor and consider measures. Levels above 25 µg/m³ are considered critical.
– Shorter periods of poor indoor climate are manageable for most people, but sensitive groups, such as children and people with lung disease, may experience irritation of the airways, says Hope.
Wind and rain often solve the problem, but both January and February have been abnormally dry with very little wind. Particulate matter has thus had free rein to spread.
– There are several things you can do to bring down PM levels. The simplest is to check that intake filters in the buildings are clean and that the correct filters have been used. It is also crucial that the ventilation systems are correctly set up and above all that they are in use, says Hope.

‍What you should do
Filters are therefore a keyword when it comes to preventing particulate matter indoors. We have therefore had a chat with Camfil, one of the country's leading companies in solutions for clean indoor air.
– There can be several reasons why particulate matter gets inside. The first thing to do is to check that no gaps around the windows are open. On days with high particulate matter concentrations these must always be closed, says indoor climate expert and sales engineer at Camfil, Nils Ledermann.
He explains that ordinary ventilation filters normally remove around 60 percent of fine fractions of particulate matter (ePM1 60%), but they do not remove everything. During periods of high particulate matter concentrations you may therefore consider using filters with a higher filtration rating (ePM1 85%).
– Finer filters will remove more of the particulate matter. For some, however, there will be a trade-off between energy use and clean indoor air. Finer filters give somewhat higher energy use, but in certain periods they are a good and effective solution, says Ledermann, adding that in most cases it is quick and easy to change the filters.

‍Free-standing air purifier
‍An alternative to finer filters is indoor, free-standing air purifiers.
– This is a local aid that effectively cleans indoor air. It is the filter quality and the number of air changes that determine the efficiency and capacity – they typically cover 30 to 50 square metres. These are often equipped with HEPA filters and are very effective. For large areas you should have several air purifiers to ensure good, clean indoor air, says Ledermann.

There are therefore several things you can do if indoor particulate matter levels are high.
– The most important thing is therefore to establish the actual conditions – whether you have a lot of particulate matter or not, says Christian Hope from Energy Control.