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Just say no to NO2

The importance of indoor air quality has never been in doubt, with mechanical ventilation with heat recovery (MVHR) systems playing a key role in providing homes with a constant supply of fresh air. However, designing ventilation systems to cope with rising levels of outdoor pollution and NO2 is becoming a major issue for specifiers. So, what cost effective steps can be taken to ensure the air entering properties remains clean and healthy, especially in such a price conscious market? Paul Cowell, Senior Technical Manager at Titon, investigates.

Air pollution is defined as ‘the release of particles and noxious gases into the atmosphere’ – such as when burning fossil fuels, including petrol and diesel. One of the main pollutants of concern is nitrogen dioxide (or NO2) which has detrimental effects on health. After all, it can cause respiratory problems, immunity to infections such as bronchitis plus, in some cases, heart disease. So, from a specifier’s perspective, it is becoming imperative to design cost effective ventilation systems to cope with the increased potential for air pollution. Consequently, MVHR manufacturers, such as Titon, are continually looking to develop products to help combat such pollutants and improve air quality.

NO2 from road transport is estimated to be responsible for 50% of nitrogen oxides, with levels highest in urban environments and near busy roads. In fact, in London alone, it is estimated almost 9,500 people die each year because of air pollution, with most fatalities linked to NO2 “emissions from diesel vehicles and other sources from within the capital.” * Similarly, research in February 2016 revealed “emissions from diesel engines have been poorly controlled and indoor air pollution has been overlooked.” *

Various indoor sources of NO2 have also been identified, including gas cooking, solvents that slowly seep from plastics, paints and furnishings, as well as air fresheners and even gas boilers. This provides significant cause for concern as, according to the BRE, the average European citizen spends at least 90% of their time indoors. **

So, having identified the fact there is a concerning issue here, what can be done to address it? Well, we know that MVHR systems are ideal for new build properties. So, as UK housebuilding moves forward, these systems (System 4) will be specified more and more into new build houses and apartments, due to their ability to remove moisture and pollutants from the air, ensuring a comfortable – and healthy – indoor environment.

Now things can be taken a step further in the cities and urban areas where NO2 is on the rise, with the addition of dedicated filters to an MVHR system to combat the pollutants found in exhaust gases from diesel engines. Products such as the award-winning Trimbox NO2 Filter® from Titon incorporate balanced flow technology to reduce NO2 to an acceptable mean concentration level of 40µg/m3 while improving indoor air quality. (Indeed, independent tests have demonstrated such units to absorb 98% of NO2 not only in normal, continuous ventilation mode but also at boost or higher ventilation rates.) ***

NO2 filters are highly effective in reducing pollutants in urban homes (including sulphur dioxide, hydrogen sulphide, hydrogen chloride and chlorine), as well as reducing the risk of Toxic Home Syndrome and the ailments associated with air pollution. They also perform well against ammonia odours. Plus, as with other impregnated grades of activated carbon, filters will also adsorb the same contaminants as impregnated carbon – e.g. volatile organic compounds (VOCs) and solvents.

From a legislative perspective, it is important any NO2 filters installed conform to the EU Directive 2008/50/EC (AKA the Clean Air for Europe programme or the CAFE Directive). This programme was launched with the aim of developing a long-term, strategic and integrated policy to protect against significant negative effects of air pollution on human health and the environment. Filter units also need to comply with Part F (ventilation) of the Building Regulations.

Utilising filter units with compact designs enables them to be installed in both intake and supply ducting. Plus, if they are capable of working with variable airflow, units can be used in small to large dwellings.

So, with people spending more time indoors, it is vitally important to utilise effective MVHR systems in conjunction with a suitable NO2 filter to ensure pollutants – and predominantly exhaust gases from diesel engines – are effectively reduced. Utilising such products and systems is another step forward in the quest for healthy homes and a high standard of indoor air quality.

* Source: “UK air pollution linked to 40,000 early deaths a year” –

** Source: BRE: Indoor Air Quality:

*** All performance data for the new filters has been derived by independent testing at a UKAS recognised test house. The testing regime was carried out to the World Health Organisation’s and European Union standards. The test report concludes that: “Both filter units performed very well, with nitrogen dioxide filtration performances of approximately 98% being achieved”.

To learn more about Titon’s Trimbox NO2 filter, please visit the website.