How is air quality defined?
Air quality refers to the nature of the air in relation to the proportion of air pollutants. One differentiates between gaseous impurities and impurities caused by fine dust particles Gaseous impurities such as Carbon dioxide, Carbon monoxide, Sulphur dioxide, Nitrogen oxides or volatile organic compounds (VOC`s), contaminate the air to the same extent as soot, smoke, fibers of wood and metal particles. The air quality can thus be ascertained by means of the presence of said impurities in the air. Also in European standard EN 13779 for non-residential buildings. The 39. BlmschV in accordance with the procedural classifications of the Federal Control of Pollution Act in regards to outdoor air.
Particles and their formation
In the air there are often many different foreign substances from natural processes that can be obtained such as soil erosion, volcanic eruptions, evaporation from the seas or natural forest fires (E.g. lightning). Also from clay, spores, pollen, fungi and other organic materials from plants and animal among others.
There is also man made pollution caused by humans such as traffic, pollution from industrial processes, energy production, traffic, fire clearing and also from agriculture. In Germany in 2002 the main causes of dust emissions were from industrial processes, these accounted for 45% , bulk material handling was 21%. Dust particles emitted from traffic such as tyre and brake wear accounted for 33 percent of total dust emissions nationwide.
The importance of air quality in our lives
Whether consciously or unconsciously our health and performance depends to a large extent on the purity of the air. While in the last few years we have been paying more attention in our everyday lives to our diet and concepts like ‘organic, vegetarian or low fat’.
We react to air impurities through our senses for example
- Irritable coughs
- Inflammation of the skin
We have become sensitized and now need react appropriately to air quality.
With more substances in the air that we are now exposed but not necessarily aware of straight away such as Ozone, carbon monoxide, bacteria Asbestos or fibres . Negative health effects are often not recognized until it is too late and can’t always be cured.
Only measurements of air quality with suitable measuring devices can lead to the necessary education and awareness. In the workplace such measurements are currently only partly obligatory. Employers and employees are strongly advised to carry out these measurements at an early stage and to initiate timely appropriate steps in the event of excessive pollution.
Definition of fine dust
Fine dust particles are airborne particles with a cross section diameter of 10 Micrometres (µm) or smaller.
It is not possible to see fine dust particles with the naked eye, only when large qualities accumulate is it then perceived to be haze or smog. These airborne particles do not sink to the ground immediately they float around in the atmosphere and can be easily inhaled. Particles with a size of 0,3µm can remain airborne for up to a year without settling.
In 1987, the US Environmental Protection Agency (EPA) introduced a "National Air Quality" standard. The standard introduced the dust particles or Particulate Matter as they are known PM and they were categorised by size. Since 2008 the EU has also agreed on air quality standards and emission ceilings (2008/50/EC)
The inhalable particulate matter comprises particles of 10 µm in size or PM10 for short. The respirable fine dust contains particles of 2,5 μm in size or PM2,5. The ultrafine particles comprise extremely small particles of 0,1 μm in size.
Dust measurement methods
There are several ways to measure fine dust, but most accurate measuring methods are costly and very time-consuming.
The current method used is gravimetric measurement. This is widely used by public institutions, cities and local authorities.
The gravimetric measurement method filters the air of fine dust particles over a 24 hour period the residue is then weighed. By dividing the dust mass, by means of the simultaneously measured air volume, the fine dust concentration is calculated in μg/m³.
An alternative is take measurements using a light scattering laser. This will provide a measurement of the size and number of particles per unit.
This enables making a calculation of the dust mass in an air sample within seconds. This provides a projection of the dust mass, it is not as precise as the gravimetric measurement but administers an accurate measurement of the concentrations of the smallest particles that can sometime be dangerous and the risks involved.