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Air Conditioning System Air Filters
27 March 2020
John Herbert
Director
In Hong Kong the HVAC air filters used in typical air conditioning system equipment, for example
air handling units and fan coil units barely conform with the standard MERV 6. Normally, these air
filters are constructed from aluminium wire mesh to comply with the non-combustibility requirement.
Environmentist John Herbert said that that type of air filter is hopeless for today's threat. A respiratory
droplet with a diameter of approx. 5-15 micrometres, it is microscopic droplet that floats indoors for
upto three hours, carrying thousands of viable virus particules.
Typically Hong Kong wire mesh air filter
The COVID-19 virus is microscopic approx. 6 nano-metres, but the air filter does not need to
stop the virus, it needs to stop the water droplet carrying the virus particules.
To be effective HVAC air filters should be able to arrest particules down to 3 micro-meters,
should be standard MERV 13 or greater to be able to arrest and stop water droplets
circulating in the air. And HVAC technicians need to exercise caution handling and cleaning
these washable type air filters.
Relative size of particules, bacteria, and mould spores || click on image for larger image