Does Your Assessment Consider The necessary Controls?
Particularly we suspect the case in high occupancy areas, little outdoor air, and when people could generate a lot of aerosols (e.g. shouting and singing). Growing evidence suggests airborne transmission may be a route of infection and ventilation has become an important mitigation factor to consider in risk reduction. Dilution of internal air reduces airborne viral transmission by reducing exposure time to any airborne viral aerosols and the chance for aerosols to settle on surfaces.
Ventilation or air conditioning system that normally runs with a recirculation mode now set to run on full outside air where possible.
All mechanical ventilation systems, extend the operation running times
Demand control type systems, the CO2 set point should be 400ppm to increase the delivery of outside fresh air.
Recirculation of air between different occupied rooms should be avoided. However, in the case of any systems serving a single space, partial recirculation of air within that space, such as through a local fan coil unit, is less of a concern.
Simply open windows. The phrase “fresh air fortnight” should be ringing in your ears
On colder days consideration must be given to human behavioural responses. A ventilation system on full outside air which is not adequately heated will create discomfort draughts. There will be the occasions the cold temperature means we have to reduce the ideal aims above.
Remember though stagnant air will spread this virus, so a balance with air changes per hour and temperature is so important to keep in mind. Sorry to say, public health at this time. outweighs the reduction in energy efficiency. caused by not recirculating air.
Viral material that lands in ductwork will become unviable over circa 72 hours, therefore systems prior to buildings being vacated are unlikely to pose any risk. In poorly ventilated spaces with a high occupancy, where it may be difficult to increase ventilation rates, consider using air cleaning devices, e.g. HEPA filters.
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