Page 46 - Climate Control News Aug-Sep 2020

Air Movement & Fans
Air movement
is key to virus control
The focus of recommendations are on air control and ventilation.
INDUSTRY BODIES AROUND THE GLOBE HAVE MADE IT CLEAR THAT AIR MOVEMENT
IS KEY WHEN MANAGING COMMERCIAL BUILDINGS DURING THE COVID-19 PANDEMIC.
ASHRAE HAS MADE it clear that disabling HVAC systems is not a recommended measure to reduce the transmission of the coronavi- rus. What is needed is air control and proper ventilation.
The Federation of European Heating, Ventila- tion and Air Conditioning Associations (REH- VA) which represents a network of more than 120,000 engineers from 27 European countries, warned infection risk can be high in poorly ven- tilated spaces.
REHVA research and technology committee chair, Professor Jarek Kurnitski, said the size of a coronavirus particle is 80-160 nanometres.
He said the particle remains active up to three
hours in indoor air and 2-3 days on room surfaces. “It is recommended to switch on ventilation systems a couple of hours earlier and also to ex-
tend operation,” Kurnitski said.
“A better solution is to keep the ventilation
on 24/7, possibly with lowered (but not switched off) ventilation rates when people are absent in order to remove virus particles out of the building.
“In buildings with mechanical ventila- tion, window airing can be used to further boost ventilation.”
REHVA has warned against recirculation be- cause virus particles in return ducts can re-enter a building in recirculation sectors of centralised air handling units. Thus, recirculation dampers
have to be closed via the building management system or manually.
Kurnitski said decentralised systems such as fan coil units that use local recirculation should also be turned off to avoid resuspension of virus particles at room level.
Similarly, he said heat recovery devices may carry over virus attached to particles from the exhaust air side to the supply air side.
In rotary heat exchangers particles deposit on the return air side of the heat exchanger sur- face after which they might be resuspended when the heat exchanger turns to the supply air side. Therefore it is recommended to (temporar- ily) turn off rotary heat exchangers during SARS-CoV-2 episodes.
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