Demand for air cleaners surged during the COVID-19 pandemic but while designed to improve air quality, some air cleaners can also generate unwanted by-products that may be harmful in large amounts.
To address this, the National Institute of Standards and Technology (NIST) has led the development of the first standardised test method for measuring chemical by-products from air cleaners. The standard provides a consistent way to assess pollutants such as ozone, formaldehyde and ultrafine particles.
Using NIST’s large chamber test facility, researchers are assessing how portable air cleaners impact indoor air chemistry. Credit: NIST
Not all air cleaners work the same way. Some rely on fibrous filters to capture particles like pet dander (the microscopic flecks of skin shed by animals) or smoke, but these filters do little to remove gases and small molecules.
Others use more active methods, such as ultraviolet light, ionisation, or catalysts designed to break down pollutants. These approaches can be effective but can also create new chemicals in the process.
Dustin Poppendieck, an indoor air quality researcher at NIST explains: ‘Most air cleaners are designed to remove relatively large particles rather than small molecules. So a filter alone might not be enough to remove all things of concern in the air.’
The new standard directly targets unwanted by-products. For example, UV light can create ozone, while chemical reactions inside devices may release formaldehyde or form ultrafine particles.
Poppendieck said: ‘If you see formaldehyde or ultrafine particles in the air after turning on an air cleaner, then you know some unwanted air chemistry is happening.
‘When you have unwanted new molecules, they can chemically react with the air to either get bigger or smaller. If they break apart to get smaller, the parts can break up into formaldehyde. If they get bigger, they form what air quality experts call “ultrafine particles.”‘
The test works by operating an air cleaner in a sealed chamber for four hours in the presence of specific chemicals, then measuring pollutant levels.
Ozone and formaldehyde are detected through ultraviolet absorption, while ultrafine particles are measured by charging, separating and then enlarging them until they can be counted with laser light.
The new standard has been developed over four years with input from researchers, manufacturers and the public.
Poppendieck said: ‘I’m excited that it’s finally coming out and will start impacting the world.
‘Now that these by-products can be reliably measured, we can be more confident that air cleaners are beneficial to the air we breathe.’
The new standard test method can be accessed here.
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