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We spend up to 90% of our time indoors, whether in the home, at school or work. Older buildings often struggle with controlling mould, whereas modern buildings are often poorly ventilated. Both can result in the build up of indoor pollutants - exposing occupants to concentrations which can be hazardous to health. If you want to measure if the concentrations of air pollution in a given environment are safe for the health of the occupants, then you might want to consider having an air test done.
There are many instruments available for testing air quality. These can be divided into two main classes, depending upon whether the pollutant to be measured is particulate or gaseous.
Some instruments to test the air quality are hand-held and useful for spot checks while others are more suitable for ongoing monitoring with results being sent to a computer system to gain a picture of pollutant levels over a period of time.
To monitor levels of particulate pollution in the air, such as dust or mould spores, you need a particle counter. This instrument both detects and counts particles by one of three mechanisms: light scattering, light blocking or direct imaging. Air enters the particle counter and any particles present are illuminated by a laser. In light scattering particle detection, the light that is scattered by the interaction between the laser light and the particle is detected by a photo detector. In light blocking, a detector notes the light that is obscured by the presence of the particle. And, in direct imaging, a high magnification camera captures an image of the particle. Light blocking is best for detecting larger particles (one micron or more in size) and light scattering better for particles smaller than this. A conventional particle counter will reliably count particles down to 0.05 microns in size. Remote or hand-held models are available; the former may be part of a more complex monitoring system, while the latter are good for 'spot checks'.
There is growing interest in the detection of airborne nanoparticles (particles of size 1-100 nanometres – that is, 0.001 to 0.01 microns) which are at this point too small to be detected by conventional optical methods. Methods for reliable detection of nanoparticles are still under development and include mass spectrometry and laser-induced breakdown spectroscopy.
There are many gases that may cause a problem with indoor air quality. Three of these are considered in more detail below:
Faulty gas boilers, cookers and car engines running in a poorly ventilated environment are the main sources of colourless, odourless carbon monoxide, whose inhalation can be rapidly fatal. A carbon monoxide detector is generally used alongside a smoke detector in the domestic or business setting. They are easy to purchase and fit in any kind of premises. Because carbon monoxide poisoning can be so serious, care should be taken to purchase a reputable detector, which means looking for the British Standard EN 50291 mark on the product and also a British or European kite mark or similar seal of approval. It is also vital that the detector has an audible alarm, rather than just a colour change or measurement, to alert those on the premises immediately. There are various technologies for detecting carbon monoxide, of which the electrochemical method is the most reliable and widespread. In this kind of carbon monoxide detector, carbon monoxide is oxidised at one electrode, generating a current which triggers the audible alarm.
Volatile Organic Compounds
Gas detection tubes can be used to measure levels of many different Volatile Organic Compounds (VOCs). They are thin glass tubes, sealed at both ends and containing a material such as alumina which can bind to a detection agent specific to the compound being measured. Binding gives a colour change whose intensity is proportional to the concentration of the compound. A pump is used to draw an air sample into the detector tube and the binding reaction takes place. The concentration can be read from a calibrated scale that is printed on the tube. Gas detection tubes are available from various manufacturers for the detection of up to 600 different gases.
A radon test kit can be bought online and consists of two radon detectors which are sent to the premises to be tested by post. A radon detector consists of a plastic hollow shell containing a piece of special plastic which records the ionising damage done by the presence of radioactive radon gas in the air. The detectors are posted back to the lab for analysis and the result is calculated as the annual average radon level in the premises. To find out more visit out Radon Information Page.
DIY v Expert
There are a number of gas detectors available for DIY use. For instance, the IQAir Particle Scan Lite is a simple instrument that can count particles down to 0.3 microns. Meanwhile, the GASTEC and Dräger Short-term, and KITAGAWA ranges of gas detector tubes can probably be used by anyone. The issue really is the context in which air is being tested and whether expert interpretation of results is required. If the aim is to detect a VOC 'hotspot' in the home which is making someone ill and the remedy is simple, such as more ventilation, then the DIY approach may be appropriate. However, in the case of business or industrial premises where Control of Substances Hazardous to Health (COSHH) regulations come into play, then expert advice would be needed. There are many companies out there advertising air quality testing. A good place to start would be the BRE Group (formerly the Building Research Establishment, founded in 1921 as the Building Research Station) which carries out measurements, sampling and analysis of indoor air quality within an accredited UKAS (UK Accreditation Scheme) framework. The Health and Safety Executive is another useful source of information on COSHH and air quality in the occupational context.