Heating Ventilation & Air Conditioning
There is no current evidence to suggest that COVID-19 is transmitted through heating, ventilation and air conditioning in the UK, however airborne contaminants can be minimised, if not eliminated, by proper and effective filtration and regular cleaning and maintenance of ventilation systems.
A clean ventilation system is an essential part of a healthy building and it is essential that any ventilation system serving a building where confirmed cases have been diagnosed are sanitised in accordance with best practice, and that any buildings where no cases have been confirmed have their ventilation system cleaned to industry best practice as a preventative measure during this time and on-going.
RECOMMENDATION – clean and change filters, clean air ventilation grills regularly, switch air handling units with recirculation to 100% outdoor air.
To book an appraisal of your HVAC plant and carry out remedial and maintenance work before you return to work please email firstname.lastname@example.org
INCREASE AIR SUPPLY AND EXHAUST VENTILATION
In buildings with mechanical ventilation systems extended operation times are recommended. Time ventilation to start at nominal speed at least 2 hours before the building usage time.
Switch to lower speed 2 hours after the building usage time.
It is not recommended to switch ventilation systems off in any buildings, even those temporarily vacated, but to operate them continuously at reduced speeds.
DEMAND- CONTROLLED VENTILATION SYSTEMS
Change CO2 setpoint to lower, 400 ppm value, in order to assure the operation at nominal speed. Keep the ventilation on 24/7.
At nights and weekends, do not switch ventilation off, but keep systems running at lower speed
TEMPORARILY VACATED BUILDINGS
Continue to operate ventilation systems continuously at reduced speed. This will ensure minimal energy usage but will help to remove virus particles out of the building and from surfaces.
Maximise the supply of outside air as much as reasonably possible while maintaining or increasing the social distancing (min physical distance 2-3 m between persons) among employees to foster the ventilation cleaning effect.
In buildings without mechanical ventilation the use of openable windows is recommended, even if this causes thermal discomfort.
In buildings with mechanical ventilation, window airing can be used to further boost ventilation, but the balance of air within the building envelope has to be considered to ensure no infiltration of foul air from washrooms enters other parts of the building when doors are opened to gain access.
In buildings equipped with centralized humidification, there is no need to change humidification systems’ setpoints (usually 25 or 30%).
FAN COIL UNITS
Including DX fan coils connected as a single split or part of a multi-split or VRF system)
Whether the unit should be switched off depends on the location, use, and occupation density of the area it serves.
If the unit serves an area occupied by one person with access of other persons limited or prohibited, and the air recirculation is all local to that zone, then there is no harm in having the fan coil operational as normal. Any contaminated droplets of moisture in exhaled air will only be recirculating to the person who exhaled it in the first place. The fan coil should be switched off when that person leaves the zone in case others enter in their absence and the surfaces by cleaned down before it is switched back on again.
If the unit serves a multiple occupied area, then it is advisable to switch it off as the potential for air flow distributing a contaminated air droplet towards other people is higher.
If the unit serves a multiple occupied area and it cannot be switched off then care should be taken as to where people are in that area in relation to the air flow emanating from the unit, and the fan speed should be turned down to a low speed setting to minimise airflow.
In all cases:
On the fan coil heat exchanger surface, it is possible to inactivate the virus by heating up fan coils to 60c for one hour or 40c each day. If possible the system should switch to full heating mode every evening, or at a time when the building or affected room is unoccupied, to allow the coil temperature to rise to 60c for at least an hour with the fan on full speed to ensure as much air passes over the hot coil as possible
Where fan coils cannot be switched off, fans should be continuously operated to avoid re-suspension of virus sediment in filters when the fan is turned on. Continuous operation and exhaust ventilation will remove virus particles.
Coarse filters within fan coil units do not effectively filter small particles but still might collect particle matter.
Increasing filter grade may put an undue strain on the fan motor causing burn out, or in the case of DX fan coils cause liquid refrigerant to slug back to the outdoor unit damaging the compressor. For this reason, it should only be done where the air flow can be maintained at a suitable level.
This document is re-produced from the Building Services Engineering Association advice and is meant for general purposes, not for reliance on in relation to specific technical legal issues, in which case you should always seek independent advice. No responsibility of any kind for any injury, death, loss, damage or delay however caused, resulting from the use of this advice and recommendations contained herein is accepted by the authors or others involved in its publication (including the Building Engineering Services Association).