Understanding new international standards for air filtration
With less than a year of the transition period for international standards for air filtration to go, Peter Dyment of Camfil explains their implications.
We all need to breathe air to stay alive. If we inhale clean pollution-free air we can expect to live for longer and healthier with a better quality of life.
Inside city buildings we can get a measure of protection from outside air pollution. By taking appropriate action it is possible to make our buildings even safer havens against toxic traffic air pollution. This pollution comes in the form of an airborne chemical cocktail of particles and gases.
The most effective solution currently available to clean ventilation air for city buildings is by mechanical air filtration. (ref. EU Healthvent Project)
Last year (2016) was an important year for improvements in standards for testing air filters. There were two new ISO international technical standards covering the performance testing of particle filters and molecular gas filters. These standards have escaped the attention of many designers and specifiers in the building-services industry.
They will enable better selection of effective HVAC air filter solutions by use of a new improved descriptive classification.
The two standards are ISO 16890:2016 for particle filter testing and ISO 10121:2013 for molecular gas filters. Added to this is the updated Eurovent energy-rating scheme which now offers an A+ energy rating for top-performing low-energy air filters.
The combined use of these standards and energy guidance give a much tighter and more accurate means of optimising air filter selection. Minimum life-cycle cost can be achieved while giving required filtration efficiency to meet clean air requirements.
Just to be absolutely clear, ISO 16890:2016 is running alongside EN779:2012 in the UK during a transition period until June 2018 — at which point the old standard EN 779:2012 will be withdrawn by BSI.
This means there is about a year to become familiar with the new filter classification system and the benefits of the new ISO filter standards.
The vast majority of HVAC air filters purchased in the UK are particle removal filters covered by ISO 16890:2016, so let us first look at the benefits of this new standard.
Firstly ISO 16890:2016 is a world standard, so it will be adopted globally, unlike EN 779:2012 which is a European standard. The new test procedures are more closely related to real-world performance. It measures a wide range of particle sizes and puts the filters into three groups.
• PM1, the best-performing filters
• PM2.5, intermediate
• PM10, the lowest efficiency.
There is also a coarse classification for gravimetric tested filters.
The public concern over levels of city traffic emissions has been rising after recent events such as the VW scandal and health study reports linking city air pollution to cardio-respiratory diseases, cancer and early onset of dementia.
The two outdoor urban air pollutants most commonly identified as health hazards are PM1 fine combustion particles and nitrogen dioxide gas.
PM1 is a mass measurement of airborne particle sizes 1 µm and below in diameter. Particles below 10 µm are invisible to the human eye unaided.
PM1 particles are small enough to inhaled deep into the lungs penetration and enter the bloodstream through the lung wall. Also PM1 diesel particles are a group 1 carcinogen as rated by the World Health Organisation, which says there is 'no safe level of exposure' to them.
The ISO 16890:2016 standard air-filter classification is descriptive. For example a good F9 class filter is ePM1 85% — where 'e' is filter efficiency, PM1 is the particle size range, and 85% is the stated percentage efficiency. Efficiency banding is in 5% increments, which means it is tighter on tolerance than EN779:2012.
Clean and healthy indoor air quality (IAQ) can now be reached by specifying a high percentage efficiency for particle filters with a PM1 rating.
Nitrogen dioxide is the health-damaging gas from traffic pollution that needs removing from air. ISO 10121:2013 testing for molecular gas filters gives a removal efficiency for target gases. A good NO2 removal test reading for a single supply air pass would be 80 to 90% initial efficiency.
High filter removal efficiencies (80 to 90%) are necessary when air pollution levels for PM1 and NO2 are routinely four or five times higher than WHO limits in UK city centres. Other problem gases commonly encountered such as NO, SOx, hydrogen sulphide and ozone can also be removed.
There are indoor sourced air pollutants that also need to be removed to achieve clean indoor air quality. These are typically volatile organic compounds (VOCs) and aldehydes such as formaldehyde.
A recirculation air-purification unit with particle and molecular gas filtration is a good solution, and there are control devices that can monitor PM or gases and operate these units in a demand-led way.
Standalone air purifier units are ideal for residential buildings. They can readily be used at the point of need on bad air-pollution days and consume very little energy compared to ducted air systems.
Peter Dyment is technical manager with Camfil.
