DELTRI+ is a multi-layer progressive filter, where the first layer is coarse, and all subsequent layers are finer than before. The virucide is “stitched” to the last and most dense layer of filter material with an advanced plasma treatment.

If the filter does not capture a virus, it will touch the filter material when passing through. A short moment of contact is sufficient for the virucide to damage the virus, disabling the virus’ ability to reproduce. More than 99% of all viruses are neutralised after passing through the filter.

Are the components used in the virucidal treatment safe for humans?

The active ingredient (i.e., the virucide) used in the DELTRI+ filter is citric acid. Citric acid is an organic compound that is also produced by many organisms. An example is the citric acid cycle that plays a major role in our metabolism. 

Citric acid has also been widely used for cleaning and sanitizing. It does not cause any known allergic reactions and it is not toxic. The citric acid used in the production of the DELTRI+ filter is suitable for consumption. It is also used in foods and beverages for food preservation and flavour. 

The unique thing about this filter is the production method, in which the citric acid is firmly attached to the filter material. This is the only way to guarantee the virucidal effect for a year. The virucide will not come off and will therefore not enter the airflow; it cannot be smelled. 

So, there is no dangerous chemical treatment. Even if the citric acid were to come loose from the filter, it is harmless. The filter material is also used to produce medical mouth masks placed directly in front of the mouth and nose. The operation and safety of these products have been extensively tested and proven.

Are there standard protocols in the testing of virucidal filters? 

The filter market does not have a fully adapted norm for virucidal filters. The independent Luxembourg Institute for Science and Technology (LIST) has carefully searched for the best testing method available. In tests conducted, aerosols containing a virus are sprayed onto the filter material. This corresponds to the way a virus would float through the air. Here lies a new opportunity for the entire filter market to set up a virucidal filter norm. 

In addition, many other tests have also been performed to determine the function of the virucidal filters. This includes accelerated life tests, tests in dry and wet conditions and tests with dirty filters. These tests confirm that the virucidal layer has a proven lifetime of at least 12 months, demonstrating virus load reduction of more than 99%.

To approach the real use of a filter in an air handling unit, the standard EN17141 (for air purifiers) was modified. During this test, air was loaded with pathogens and pumped through the filter. This test confirmed prior results on the VLR, but also showed that the filter is active against bacteria and mould.
 

Will DELTRI+ allow us to reactivate recirculation functions in our AHUs?

In many COVID19 prevention recommendations, including Systemair’s, it is recommended to turn off recirculation functions in AHUs and switch to 100% fresh air supply mode.

Recirculation was utilised in many situations before the pandemic to save energy (e.g., during low occupancy at night in a building or when CO2 levels in a room are low). In an intelligent ventilation system, this was “normal” and made sense.

Many building operators and owners have contacted us over the past months as they would like to activate recirculation functions again. First, however, they would like to have the confidence to do so.

DELTRI+ is a straightforward solution in this respect. While high-quality ePM1 filters already help, the DELTRI+ technology offers an additional safety net, enabling (partial) recirculation again to save energy.