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Last edited 17 Feb 2020
Clean indoor air for healthy living - New air filter standards
Breathing air is a fact of life. Unfortunately, the air that comes into our bodies often carries unwelcome pollution. This air pollution comes in the form of a mix of toxic particles and acidic gases.
Urban traffic air pollution has been a rising public concern especially since the Volkswagon scandal demonstrated car manufacturers have been more interested in dodging emission tests than providing clean running diesel engines.
The government is also slow to take action to remedy the situation, having been responsible for previously promoting use of polluting diesel engines. If you live in a polluted urban area or close to a source of air pollution such as an arterial road, industrial plant or power station then you will be exposed to this invisible health hazard.
These airborne contaminants can penetrate lungs and enter the bloodstream, causing damage to health and diseases. A study from Lancaster University shows that ultra-fine combustion particles generated from high temperature fuel combustion have been found in heavy concentrations in the brains of people suffering from early onset of Alzheimer's disease and dementia.
For a start, we spend typically about 90% of our time indoors so our direct exposure to outdoors air is reduced as a result. The buildings we occupy at work and at home to some extent act as a haven against this threat to our health.
There are also air monitoring and measuring devices that are relatively affordable coming onto the market. It is now possible to use newly available and affordable devices to measure pollutants of concern and compare them with published World Health Organisation (WHO) limits. Some of these measuring devices also have the capability to control air purifiers and air cleaning devices.
The two outdoor urban air pollutants most commonly identified as health hazards are PM1 combustion particulate and nitrogen dioxide. The WHO and Royal College of Physicians recent report ‘Every breath you take’ goes into detail about the health implications.
PM1 is a mass measurement of particulate matter one micron diameter and below in size range. A micron is one thousandth of a millimetre. This is very small as any particle below 10 micron dia. cannot be seen unaided by the human eye. A human hair is typically 70 micron dia.
Once the seriousness of the problem of polluted indoor air has been established then action can be taken. Although a relatively airtight building will offer some protection against urban traffic pollution, there will be penetration into the building by opening windows, doors, passage of people and ventilation air systems. Typically, the penetration for PM1 and nitrogen dioxide will be in the range 30 - 70%.
The only effective solution currently available to reduce this level is to use mechanical air filtration.
ISO 16890:2016 enables selection of filters to remove PM1 particulates to a high level of efficiency. In the new classification system ePM1 85% would equate to a good F9 filter, but is more useful and informative notation to the end user because it actually says what the filter will achieve. Filtration efficiency ‘e’ will remove PM1 size range particles to an efficiency of 85%.
For the removal of molecular gas contaminants such as nitrogen dioxide the new World filter test standard is ISO 10121:2013. A good nitrogen dioxide removal test reading for a single supply air pass would be 80 - 90% initial efficiency.
This is fine for filters in large air handling unit systems in central London but what about me at home? Is there another option available apart from keeping windows and doors shut on bad air pollution days?
The answer is that a good recirculation air purifier unit positioned close to the person needing clean air will give the healthy solution needed. A well designed unit can provide E11 – H13 Hepa particulate filtration with molecular gas filtration for the removal of nitrogen dioxide, but also the commonly encountered indoor sourced air pollutants such as volatile organic compounds (VOC’s) and aldehydes such as Formaldehyde. These units are especially valued by asthmatics and allergy sufferers.
- In several aspects, the new test procedures are more demanding than the existing standards. This will lead to higher filter performance, improved indoor air quality, and greater protection of human health.
- The new test procedures are more closely related to real-world filter performance.
- The classification system is related to filter performance against three different sizes of particles.
- Importantly, the smallest particle fraction of the three, so called PM1, best represents the very fine particles that are known to be the most harmful to human health.
This blog was written by Peter Dyment, Technical Manager at Camfil Ltd.
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